Help me figure this out - M103
 

I just got a 1990 300E. It seems to be a bit low on power...sometimes going up hills I need to completely floor it and it won't really accelerate much. Really noticeable above 2500rpm. I'm not really sure where to start...I have a bunch of parts on order like filters, plugs/wires/cap/rotor for a tune up. It sounds like there might be an exhaust leak due to a sound (sort of a hissing) but really only hear it under load and somewhat at idle. Would all of this indicate a failing fuel pump? Air pump leak? What would the symptoms be of each? Most of my gas engine experiences were with well...not overengineered engines.

I'm still trying to get my head around all of the acronyms on this board, much more complicated than the old diesels!

Car has in between 100k and 120k I believe, odometer is slow/inaccurate.

Well start with the tune items you bought and make sure to replace all the idle air hoses. Shoot some carb cleaner around the idle control valve, injectors and listen for any vacuum leaks. Start there and if you have done the spark plugs, wires, rotor, cap and idle air hoses and the problem still persists we can go from there.

Until then it will be very difficult to get a good baseline. Just snoop around underneath to find the exhaust leak. That or pay a local guy $50 to patch wherever the hole is.

Any excessive oil consumption currently or before? Cat assy could be plugged up nicely.

Fuel pumps become very loud when about to die.

I agree, start with the basic stuff and go from there.

Are you in an area where you have to get a smog inspection when you buy a car? What were your readings? Those could shed some light on where the problem might be.

Still have the temporary tag on, need to get it tested (only had it for a few days). I wanted to make it run nice and perfect before going for the smog tests. I have to drive up to CT to have it inspected and tested so it needs to pass first time or I'm stuck....keeping my fingers crossed. My parts are coming in today, will get to it if I have time before my night class.

Hitman may have "hit" it; all your symptoms are consistent with a clogged cat. I had one on an old Caddy, and it did just that - ran fine at low speed and idle, but just wouldn't go under power. If the hiss is coming from the exhaust ahead of the cat, then there's another strong indicator.

DG

uh ohhhhh, that would put me pretty deep into this car in terms of money spent. Anyone have any experience using a universal cat on MBs? The one on PP is $700 :eek::eek::eek: I know decent high-flow ones only run 100-150 bucks. It does make sense though, I'll have to get it up on the ramps and take a look under there.

Edit: The PO did mention oil consumption as a problem with the car...I imagine the valve seals are worn, common issue. I didn't really think of the down-river effects of it though. Its beginning to add up, but I don't have the money for a $700 cat. I think I'll get a universal one and have a muffler shop weld it in.

Also side note: small victory in replacing my ignition lock cylinder, raised my spirits.

Yes, I was thinking that too, that's one of the reasons why I wanted to know the results of the latest smog test. I didn't want to say "Cats" until we had more info cause O.P. has three of them to contend with.

And while I agree the cat(s) are the front runner on the suspects list, high oil consumption doesn't guarantee bad cats. The 89 in my sig really swigs the stuff but the cats haven't given up yet!

And no, I'm not gonna bother with the valve seals on a car that has over 232,000 miles on it and isn't worth more than a 1,000 dollars! I love Benzer 1 dearly but that just ain't gonna happen! Too much else to do!

I've heard of upgrading to Mustang Cats.Jegs.com

103
 

Do not forget the fuel filter replacement if there are no replacement records
mak

Do you mean two precats (one per pipe coming off of exhaust manifold) and one main cat (after the 2:1 collector)? I've been looking at exhaust diagrams all morning. I wonder what the best way to test these would be. I could unbolt the main cat, but couldn't run it with a sidepipe dump since the O2 sensor manages the engine once it warms up.

Eventually I'd be wanting to put on a turbo with moderate boost so maybe universal cat with 3" back exhaust using universal stuff might be useful. Idk, I'd have to consider that.

update today. I put on the new distributor cap, rotor, and replaced the ignition wires. Naturally me being me, I managed to break something but luckily it was just the wire cover on top of the valve cover but still :mad:. Anyways power seems to be a BIT better, not too much of a difference (not that I expected too much). Good thing I changed the cap/rotor though, it had quite a bit of buildup on them.

Going to do the fuel filter next, that might be the answer (I really REALLY hope) to some of my problems. I also think the trans needs to be tuned. I went looking for the bowden cable, but didn't feel like taking off the air cleaner, maybe tomorrow.
Thank you for all your inputs thus far! I'm pretty familiar with the diesels but the learning process has begun again for the gasser. Currently trying to price out turboing this bad boy, but most importantly to get it in perfect running condition before any of that.

People tend to forget about hours on a motor too, even at 100k like you think (probably much higher, people lie when selling vehicles always). Hours will wear stuff too... pull the old plugs and take a peek for any oil build up. Cap/rotor/plugs will not last too long due to the high cruise RPM from this motor. Same goes for the fan belt/accys.

I have fairly heavy build up on my M103 on a few cyl, head R&R is planned for this summer. My oil consumption/loss is very high as my head gasket is also seeping up front. I am talking around 1 quart per 500 miles type of use.

Granted the '90+ cars received 'hardened' guides supposedly from MB, I would suspect a worn head easily. Remember also, if the car has not been driven to hot often the cat converter will not light off and can plug up too.



I would hit the main cat body with a mallet and see if you can hear any rattling... along with S-class Guru, a pal of mine had a Turbo Buick where the cat died and the vehicle would barely run past IDLE speeds. Blew out the downpipe donut gasket it was so plugged. Hacked the cat off and all was well.

So, of course do the fuel filter and see where that gets you. If not, then I would pull the cat assy and ream out the precats, they are only there for cold start emissions. You could also ream out the main cat, but the fetch decent cash for scrap so I would just cut it out and sell it.

Do not waste your time putting a turbo on this unless you convert to actual EFI and have the head redone. CIS is crap.

Car will still run without an O2.



Magnaflow/Carsound have universal high flows that are application specific to fit your ride for a good price.

Sorry, site double posted. Please see below.

Yes, the two pre-cats and the main cat. I don't know how strict your smog laws are but out here in Calif you can only replace your cats with stock cats or properly "certified" aftermarket cats. (Different states have different rules).

And while on that topic, here in Cali you also won't be able to pass smog unless your non-stock turbo kit has been "certified" by it's maker which of course doesn't work for us because there are no "makers" of turbo "kits" for these cars anymore. I'm gonna get around that by running my turbo car on an alternative fuel. Not trying to discourage you, just want you to be prepared for what may lie ahead.

Like you alluded to, "once it warms up", the car goes into closed loop, but before that happens, it is in open loop mode so there would be no harm in doing a full throttle power run with the cats off. If one or more of the cats are bad, your power will be back. And if I'm not mistaken, these cars are actually in an open loop mode anyway when they are under wide open throttle operation even when warm so it really shouldn't matter anyway. Still, I'm hoping somebody else here has a better test than mine for the cats. The mallet method doesn't work all the time because these things often just melt solid inside which means no rattling pieces, just a plugged cat. Go ahead and try it though, as it may catch the problem, just don't think that all is well if it doesn't rattle cause it/they may still be bad/plugged.
Regards, Eric

That is because CA is in outer space with many of its demands/laws. He is in PA aka 49 state legality. Punch out the precats, weld in new main... off you go. Retaining a cat is not going to hurt any noticeable power on that fire-breathing 177hp motor. Catted v Non-catted M103s had less than a 10hp flywheel difference in output... 6-7hp I think is the difference WHEN NEW. On a chassis dyno you will not see the difference. BMW also had a catted version of the 8:1 M30 for the older E23s and a non-catted 8:1, power diff was about 8hp crank again.

I agree on the mallet, but it is an easy first test. Hell you can just put your hand by the tailpipe and have someone rev the motor up and feel for high exhaust flow. Plus you can see if it will rev to redline in park... it may not.

Plugged cats also harm 603 Diesels badly, I have repaired two others that were so plugged the vehicle struggled to rev to 3000rpm. This of course is in addition to making nearly no boost pressure. Talk about a slug. Mine was plugged also. Key there is 'was' plugged. ;)

I THINK CIS cars attempt to retain stoich A/F even at WOT. i.e. no power enrichment. You would have to attempt to find a dyno of one with air fuel recorded, but I swear I read this some place. Just another reason I do not like CIS.

Yes, it's likely his Penn. laws will let him get away with stuff that I can't get away with here, I'm just saying he should know what he can get away with before he tries it so he doesn't have to spend even more money later to undo something he can't get away with. Or more money having to bribe a smog guy like some folks I know. :o

The difference between the cat M103s and non-cat M103s was 13 hp (177 vs. 190), admittedly not very much, but still a little more than 7 or 10 hp. Just keeping the facts accurate. ;):P:D
Regards, Eric

Do you have a link for the 190hp non cat version?

Thank you much for the info guys. I am actually registering the car in CT, but the laws are not much different than here in PA. I've been thinking about it and I think that I will go through emissions just for S&Gs, since the PO passed about a year ago in Jersey (tighter emissions/inspection laws). If I fail I'll order a universal cat and have it welded in within a few days, pass will give me more time. The 100k estimation is my own, the odometer reads 81k but its going slow. 100k was just a rough number from the condition the car is in. Guess I'll see where this leads me.

Turbo idea is a long-term one...would be converting to EFI (probably megasquirt) and all the fun stuff associated with that. Interesting post on the performance paddock section notes that the 350SDL is basically a turbo manifold that will fit the M103 for a T3/T4 turbo. But, as the #1 rule in modding states, need to get everything working 100% before any mods.

I have my precats hollowed out on my 300TE and have a high flow Magnaflow cat downstream. What type of power gains do you think I got from this? (I did it mainly for $$ reasons rather than HP...was much cheaper to hollow out than to buy precats)

Looks to be just what I am planning on doing in the near future. Do you happen to have the part number still available? It looks like the 94xxx series is the popular type. Any total cost figures (welded in by exhaust shop or something)? How are your emissions results looking? If you don't want to post in the thread here feel free to PM me, any specific info would help to steer me in the right direction. Thanks!!

Tuff Metal
 

Yesterday I used a cicular saw up side down to cut off down turned tips.It was a concrete blade.Still picking metal out my arms.
See son in law borrowed my other tools.

Well I passed the CA smog this year with the setup. I paid the exhaust guy I think $320 all said and done.

I don't remember which model cat he used. I have my exhaust on the garage floor right now waiting to go in once the transmission is in. Is the model # written on it anywhere? Want any pics?

I read it in one of my old Car and Driver mags where they did an article on the European 300E just before the "Americanized" version came here. So it was a late 1985 issue I reckon. The author was ole David E Davis Jr. hisself. That issue is packed away in a box somewhere and even if I found it, I have no ways or means to scan it. Maybe you can find it on the web somewhere or in the library. That 190 hp number really stuck in my head cause that's what another I6 that I love makes (the AMC/Jeep 4.0 HO). And get this: the earlier pre-HO 4.0 made 177 hp! (The first one made 173 hp.)

Actually, now that I think about it, there is a thread here where European members talk about their 190 horse M103s. I'll try to have a link for you tomorrow night.

Gee, this isn't cause you don't believe me now is it? :P;):D
Regards, Eric

What?!? It would seem that you are gonna have an unfair advantage against the 525i wagon this April 3 that you didn't tell anyone about........ ;):D:cool::P

Wait a minute son, you're getting ahead of yourself here. You haven't even established that your existing cats are bad yet.

tbomachines - as a previous longtime M103 owner I'll throw in my $0.02...

Are you sure your engine actually has a problem? If it runs and idles fine, gets proper mileage, and posts good e-tests results, I would wager there is nothing likely wrong with it other than age.

I always felt the M103 was underpowered for the W124 chassis. The M104 was a much better fit in terms of how the car felt and performed. I've driven both.

The M103 only had 177 hp out of the factory IIRC and with the age of yours, that number is probably down around 150 by now due to wear. For the weight of the car, that is not a lot of power. Minivans would always burn me at lights, quite depressing really. :o

So if everything basically checks out, I would stop hunting for issues that are likely not present and just enjoy driving it. A tune-up (replacing common items) is fine but I wouldn't start throwing money at things in the hope of seeing significant performance gains.

If you want power going up a hill get an M104, or better yet a 400E or E430.

As far as oil consumption, are you sure the engine is burning it? Look for leaks, the M103 was notorious for a leak at the front passenger side of the engine at the camshaft cover. The leak would show oil on that side of the engine, running down towards the alternator.

Good luck!

Yeh but I got a rough idle and ran into some problems with my front pump...so not sure if the car will be on the road for April 3rd yet :( I'm waiting for a few people to email me back over the part I need...Until then I'm sitting idle.

Well vintage car mags I have also said my Ljet 745i turbo was 225hp when all factory documentation rated them at 252hp... That is a pretty significant disparity in power.

Hell Wikipedia shows 185hp catless. But how reliable that information is can be disputed as any fool can write up that information. http://en.wikipedia.org/wiki/Mercedes-Benz_M103_engine

Like I said, either way the power difference (cats/catless) is something you will not notice in the seat of the pants and is nearly in the realm of dyno error for rear wheel HP/TQ.

I'm not going to buy anything exhaust-related until I get a smog test. As I mentioned earlier, there is an exhaust leak somewhere up the pipe, regardless of whether or not the cat is plugged. You can hear it alongside traffic, jersey barriers, fences, etc. when driving along, especially accelerating from a stop. It does burn a bit of oil, though not much....I've driven it about 500 miles since I got it and it is just a tad lower on the dipstick. No leaks around the engine, it is spotless.

I know the car is underpowered in terms of performance numbers but my 300SD shouldn't be able to outrun it.....I live basically on the edge of a river and after crossing the bridge, there is a massive hill on the other side. The 300E loses speed with the pedal to the floor, even after it upshifts. I think the trans needs to be tuned a bit (it upshifts to 2500 rpm, have to put it into "2" to get it to maintain speed at 3-4k). My 300SD has no problem going up that hill and that is a significantly heavier car (especially with all the crap I have in the trunk), though a bit more torque. Along with a transmission adjustment (bowden), I'll probably check/tighten up the throttle linkages too....

Idle is a bit rough and shuddery as well. I am going to go through and clean all the sensors I can, along with testing them out via multimeter and diag port just to make sure there is nothing odd going on. I've the the weekend ahead of me, might as well put it to good use!

Edit: also been getting below expected mileage...gone 120 miles mixed city/highway and it is down half a tank, haven't done the figures yet but it seems quite low.

Honestly, my well-tuned....M103 with a fairly low mileage bottom end, and a fresh top end has oodles of power (even at 5500ft). I believe it is very close to the factory spec'd 7.5sec 0-60.

I can't wait to take it down to sea level. Not sure why people bag on the M103 so much. Honestly the published 0-60 times for the late M104 engined cars are slower than that of the early M103. Especially with first gear start, the 300E is a joy to drive. IMO, the M103 redlining sounds ten times better than an M104 under the same circumstances. No, it's not going to blast people from the line. But 20mph rolling starts, it's going to take something with considerably more power (or less weight) to put it to shame. The M103 loves to rev and I think some people are afraid to drive it hard, but that is where it performs the best. One of the favorite parts of my usual commute is a ~1/2 mile considerable up grade portion of highway, punching it at 55, and by the top of the hill I can just touch 100mph.....it's quite fun. I think many people don't realize how nice a proper low-mileage/maintained 300E engine is. :cool:

you are experiencing the difference between a gas and diesel vehicle. A diesel vehicle will offer much better low end torque because of the design of the engine, the chemical structure of diesel. A gas engine is only 20-25% efficent and a diesel is 50% efficent in terms of combustion.

As for the fuel mileage problem sounds lambda needs to be adjusted, fuel injectors to be checked. A common place for those to leak oil is on the right side of the motor at the front because of the head gasket design. I would do a compression test and cylinder leak down test to see the health of the motor. do you know how to do a cylinder leak down test?

Hey, I'm not bagging on it at all, it's a fantastic engine! My 300E went to 333,000 Km all original - zero work done on the engine. Just saying it is a tad underpowered for the chassis is all. Just MHO, not fact. I thought it was a decently peppy engine until I got the E430, which changed the entire picture. Part of the issue I think is also that 4-speed tranny. It's hard to find a sweet spot and it has a mind of its own in terms of shifting. I got tired of either slamming it off the mark to force a 1st gear start, or using the shift down and back up method at stop to get the 1st gear start. That obviously makes a big difference, but I do remember times when I hit the gas hard (like passing on a hill, etc.) and I didn't get as much power as I'd hoped for.

The diesel vs. gas is a good point as well.

I guess all I am trying to say (in a long winded way) is that perhaps there is not as much wrong with the engine, but rather it is not delivering as per tbomachines' expectations in this case?

Yours sounds rebuilt and I'm guessing that would make a significant difference compared to a higher-mileage specimen.

I've driven an M103 300E, a M104 300E and a M104 E320 and in all cases the M104 pulled significantly harder than my M103 ever did. Nothing scientific, just seat of the pants observation. Significant differences in the two.

The M103 however, has been touted as being one of the toughest I6's around. Just check out the Performance board on this forum and see what those guys are doing with them and turbos...500HP+! :eek: :D

That would solve the little hill problem. ;)

The performance numbers for the 300SD and 300E should absolutely not match as mine do. Of course the diesel will have more low end torque but the gas engine should leave the diesel in its dust in a drag. My cars are about the same performance level...not good. I've driven a number of gas vehicles, not new to them...just new to this car.

I agree I need to do some diagnostic work to fiddle with the AFR and fuel injection system. I noticed today that when I rev it in neutral a bit and let off the gas, it comes VERY close to stalling, which would indicate running a bit rich (in my past experience at least). Fuel pump is pretty loud too...crawled under there while the car was running to check it and for exhaust leaks. Cat-back is all like new, definitely replaced but with OEM pieces ($$$). All that I've got left to do is really to start picking this thing apart and check all of the sensors. Will update this thread as I do it.

Thank you for all your input!!

Edit: the line about the fuel pump was supposed to be accompanied by this bit--tried to get the fuel filter off but damn those nuts were STUCK. Had a tough time getting leverage but still....Blasted it with PB, letting it soak a bit then I'll get at it again tomorrow. Looks like the filter hasn't been changed in forever so that'll be a good thing to do for sure.

Indeed. It just seems most people resign themselves to the fact that the stock M103 is never going to be fast. The transmission on mine is also quick, snappy and changes gear at the right times. If you learn the shift points (and double kickdown points) and drive accordingly, you can make the 300E look damn impressive. Mine just had a "proper" head job done, nothing too fancy. The compression on my motor is a little higher due to the fact I had the head skimmed by the machine shop the smallest bit. I looked a good ten or so 300's before choosing mine. It doesn't take much neglect over the course of just one owner.....to turn these cars into granny shifting pigs that can barely get out of their own way......;)

In its day the 300E was a FAST 4 door sedan. I mean the non-turbo 944 was almost a full second slower 0-60. It is not FAST by today's standards, more like QUICK.....As you said, or someone else; minivan's can now crank out sub 8 second 0-60's. But it's all in how you get there. And how reliably you can get there well past 200K. :D.

I also picked up a 95 540i just recently, now that would definitely smoke the W124 for breakfast and lunch....probably similar performance to your E430. V8 sedans are a whole different animal.Boy that thing is FUN on the highway. :D:D:D:D:D.......I just prefer the silky smooth high revving I6.

Sorry for the threadjack BTW. ;)

Yep, agreed.

I'd love to drive my 300E hard at times and that I6 sounded fantastic when you opened it up. It had a great steering feel as well, nimble yet firm. The only thing that really stank about the 300E was the stereo...:D Mind you, I upgraded that as well (I wrote a DIY article for this site re: amp install).

540? Nice. I considered one, but a) didn't want to stray from my MB comfort zone and b) needed a bit more interior room (kids/car seats). Great car though, and it would likely beat the E430 all-around as well.

Cheers,
C.

Good luck, hope you get it sorted out!

LOL thanks me too! :D I'm sure I'll have more questions as I go through everything....

I know somewhere in this thread there is info on the Euro 190 hp M103. I just can't remember which page. http://www.peachparts.com/shopforum/showthread.php?t=32224

Some info and links to videos and photos of actual 300E, 400E, 500E and 540i dragstrip experiences: http://www.500ecstasy.com/forums/showthread.php?t=6323&page=12

A video of my 400E running a 14.551: http://www.youtube.com/watch?v=sOpeNXP0sMw&feature=channel

The final word on the 540i vs. 400E/E420 debate: http://www.peachparts.com/shopforum/showthread.php?t=172171 The best info is near the end of the thread on the last page (but not right at the end).;)
Regards, Eric

My 1995 540i with the 4.0L M60 is spec'd at 6.2 secs 0-60 (AUTO). The 1993 and 1994 540's were significantly slower for some reason. Mine gets 18-19mpg around town, with a lead foot, and about 24-25mpg highway. The 6 Speed 1995 540i with a Dinan chip is exactly as fast as the 500E, and would have no problem keeping up with an E34 M5. 5.5secs 0-60 for the 6spd. I've driven both....the 6-Speed is scary fast. :)

I am not sure if this will help but did you look at coils for arcing. Mine cause all kinds of problems at under 2000 RPM . Just a cheap thought . I also went nuts and drew no codes Spent 1k and it was $120 parts
Worth a look IMHO.

Its just that I very seldom see anyone mentioning coils for anything intermittent, under load , or in any other way obvious , and I from experience going thru 3 certified MB techs know better .

Do not over look a posssibilty that is free to see . Any arcing , white stuff like everyone describes for caps/rotors. It was on one of my coils instead

Well bring it out here son! Our next track day is a week from today Sat, April 03, 2010 in Fontana. We'll line 'em up! http://www.peachparts.com/shopforum/showthread.php?t=251933&page=7

I'll make you a deal: if you'll come out to our next track day, I'll give you that ECU for your M103!

This is my knappy 400E holeshotting a 97 540i 6spd: http://forums.turbobricks.com/showthread.php?t=193034&page=7 (Go down to post number 169, first and fourth pictures). In all fairness though he wasn't on top of his game yet cause it was in fact the track's first run of the day and the track was still cool and damp. (but he got much better later in the day, see next paragraph). He only ran a 17.73 on that first run. Still makes a nice picture though don't y'all think?

That 97 540i 6spd. got better as the day wore on. Here he is seen spanking a Camaro while running his best E/T of the day, a 14.908 at 97.33 MPH: http://www.youtube.com/watch?v=0og-7EoUJ20

My best E/T of that day, a 14.530 @ 97.22 with this car's best ever 60 foot of 2.297 despite the track still being cool and damp, was ironically the run against him. That E/T is even with me hitting the rev limiter! (of course nobody got a video of our run but thanks to one of my Volvo buds it is at least caught on film). My last run of the day was a 14.727 @ 97.57.

For the record, this is kind of a "slow" track, over 1000 foot elevation, a so so launching area, and the last half runs slightly uphill! Don't forget those times you see published are corrected to sea level and cool temps (60 F I believe). The 14.476 in my sig corrects to a 14.07 @ 101 MPH!

Bottom line: Benzes rule :P:P:P:P;):D:cool: Bimmers drool! :o:o:o:o

Back on topic now I would add to Peter's post that spark plug wires are another very overlooked part under the hood. Look for arcing there too.
Regards, Eric

Eric,
You really drive your car like that? I baby mine like a granny till I get to 70 MPH at least and then if I feel safe I will downshift it once to 110 MPH but only when I have good cop connections , and feel I can talk my way out of a speeding ticket.

Benz's drive like yours does? Coulda fooled me :)

Thanks guys!

I did replace the cap/rotor/wires already as tune up items. The coil still looked good and I haven't seen any arcing under the hood at all. Haven't made much progress since then, just another try at the fuel filter (no progress). I'll be driving it up to CT this coming weekend for registration/tags/etc. I have more tools and time up there so I will hopefully get to the bottom of it. All I have left for the initial tune up is the fuel filter and replacing the front brake rotors since the current ones are warped...have slotted ATEs waiting to be put on.

As far as power is concerned...I can't wait to get this thing up and running/tuned properly despite its inherent slowness. The engine is smooth as can be while running, can't wait to unleash it!! A T3/T4 turbo should do wonders :D

Update: Passed emissions today-- it did really well, way within the boundaries. Now, to make it run smoother and more powerful...pretty much going to take the entire day tomorrow to work on the car and polish it all up.

:D

I'll have to take a raincheck on that invitation. But I'll be out in CA sooner or later. Most likely to buy another Benz. LOL @ at the Bimmer's first run. Doesn't a well tuned 300E run somewhere close to a flat 16-16.5?

Pshhhhh, I don't even really own that 540i. It's just a fix-n-flip sorta deal. It just so happens to be kinda fast so that's a cool bonus,I love to beat on it. But it's a piece of shiat compared to the W124. Seriously. Sporty my ass. I also never knew how slushy BMW auto gearboxes were. Damn. The 124 gearbox is 10 million times better. My 300E still feels like a stronger car than the 540i, but the BMW can throw you back in the seat pretty good. But it's comparing apples and oranges (Quad Cam 32V V8 vs 12V Single Cam I6). But none of the E34/E30 stock 6 cylinder BMW's can hold a freaking candle to the M103 I-6. There's a reason why! .......I've been thinking I might start looking for a nice 400E. They are soooo cheap if you wait to find one.

If you go that route, try to get an early 93, one made before 03/93. That's when everything came together. You will get a closed deck, metal oil tube, 11.0 to one compression, 32 valve, 4.2L V-8 engine in a car that looks just like your 300E. Talk about a sleeper!
Regards, Eric

Were you still on the old cats?

Keep us updated!
Regards, Eric

Yep, old cats (I assume original) but newer OE catback system (can't even imagine how much that went for at the dealer...). I changed the fuel filter yesterday and the old one appeared to be original with the car :eek:. It was really heavy as well even without any fuel left in it, I think I'm going to cut it open just to appease my curiosity. The car does seem marginally faster by the seat of the pants dyno after doing the filter change. Unfortunately, the fuel pump is pretty loud (assume from running on a clogged filter for so long), so I will need to replace that at some point. I do think that is contributing to the "hissing" sound on throttle, but it would be more of a constant than noise under load. Still have a lot more work to do today, will report back at some point.

Ok - update as promised:

Changed out oil/filter for 15w-50 synthetic. Also changed the transmission fluid and filter. I was quite unhappy to find a bunch of metal shavings on TOP of the old filter, though none in the pan. The fluid was a little on the brown side, but smelled okay and not burnt. Seems to be shifting okay now so hopefully the fluid flush was all it needed. The fluid and filter clearly hadn't been replaced in at LEAST 50k (my diesel had 45k on its filter/fluid and it was better condition when I changed it out). Also replaced spark plugs finally, the PO had Champions in there, most likely with resistors. I changed them out for the proper Bosch plugs. I also lubricated the entire throttle linkage assembly, tightened the throttle cable and gave a turn to (tighten) the bowden cable. I cleaned around the lip of the MAF sensor with carb cleaner and a Q tip, making sure it wasn't getting caught on it.

Tightening the Bowden cable (moving shift points upwards) seemed to make a huge difference, now the engine is actually using its ideal hp/torque bands under heavy acceleration. Also, the idle seems to have smoothed out a bit (spark plugs?). I floored it coming out of Home Depot and noticed there was a nice bit of smoke behind me. Unburnt fuel perhaps, but maybe a good ol' italian tune up spew of soot :D there was an M3 behind me.

I still think I can improve on power, but it has DEFINITELY seen an improvement since I got it. Right now, I feel accomplished. Just need to get the slotted rotors on tomorrow and give it a nice wash/wax/polish.

Edit: I also did the mileage figures for my trip from Philly to CT - 29 miles a gallon. I had to double check everything to make sure I did it right because I didn't believe it could be that high...but it was GPS tracked and I actually overfilled at the gas station so it was marginally above 29.