M103 Misfiring/fouled plugs issue....
 

Our 300E seems to be having an issue with fouling the plugs.....

I pulled the spark plugs a few days ago and the plugs from cylinders 1 3 and 6 were pretty coked/fouled up with carbon and slightly oily. #6 was by far the worst, the entire electrode/gap was completely coked over... I attributed this to it running rich up until I solved its idle control issues. (had it running mechanically with stuff unplugged for about 700 miles or so) So I cleaned them, re-gapped them and put them back in....ran great. Now its misfiring again, only a couple hundred miles later. On top of the misfire, when you turn the car off, an oily smoke/mist emits from the exhaust pipe. It smells like burnt oil/gas. I'm assuming its oily gas burning off in the exhaust from the misfiring cylinder(s)? It really doesn't use all that much oil....we've driven it nearly 1800 miles since I did an oil change on it with M1 0w40....and I've only added maybe 1.2 qts to keep it near the top. Should I use a different (thicker) grade oil to combat oil burning/leaking?

Tomorrow I am going to pull and inspect the plugs again as well as swap the distributor rotor and cap with new ones....the previous owner(idiot) ran resistor plugs in it, who knows what that did to the distributor...

Any ideas? It doesn't seem to have a head gasket problem....coolant is clean and the oil looks fine..no overheating or pressure in the hoses....so there's no mixing going on or anything, and no coolant is lost at all.

Engine only has 135k on it....

Anyone?

Make sure your Vacuum Modulator isn't leaking. Mine did once and burned trans. fluid through the intake manifold coming from the vacuum hose that connects to the VM. When my trans. fluid was low, I checked the VM vacuum hose at the intake and I could see fluid in the vacuum line. Replaced the VM and problem solved.

Just a thought.

I'll double check it, but I don't think its leaking.....trans shifts great and doesn't lose any fluid. Plus the line was disconnected when I got the car but was not oily inside....

Oh you diesel guys, just helpless with the common cars ;~)

Sounds like you might have a valve seal issue. Not terminal, but it will require removal of the cam cover and rocker assemblies, valve springs and retainers, pressurize the cylinder through the spark-plug holes to keep the valves closed, or TDC on the cylinder you're working on, not sure how it's done on the 103 but I'm betting someone here will.

Funny thing about gas engines, they have this thing called "vacuum". It is greatest when the engine is running closed-throttle, watch your mirror when exiting the freeway or just downshift when coming to a stop. Tell-tale sign is to run the car up in RPM in 2nd gear, let off and let the car slow back down a bit, then give it gas again. If you get a quick puff of blue each time you push the gas pedal trying this, it's valve seals. With a stickshift it is easy to see, automatics hide it a bit.

1st gear is too jerky, and 3rd is probably too fast to get a good puff in the wind.

Good luck.

<<edit>> Also, leaking valve stem seals often cause a blue puff when starting the engine.

Valve Stem Seals.

Look like this?

http://img.photobucket.com/albums/v2.../dad/Plugs.jpg

It doesn't put out any blue as far as I've been able to tell....if you drive gentle for a while then "punch" it, it actually lets out a slight stream of black smoke, then it clears up. Oil consumption seems to be too low to be valve seals....less than a qt per 1000 miles.

Hey now, I am gaining ever more love for diesels because of this car! :eek: If this thing keeps being a pain to maintain (funny how that rhymes :o ) I'll be looking for another diesel!

Actually not. They were black and sooty. With hardened black carbon deposits all over them. Didn't really look like that at all.

They looked a lot like this, just not as wet:

http://www.essexbikers.co.uk/referen...vy_carbon.jpeg


Tomorrow I am also going to check my spark plug wires....if tested with an ohm-meter, what should their resistance be if they are "to spec"?

Leaky valve seals don't really consume much oil. The probem is that when they leak the most is at high-vacuum, which is when the throttle is closed and there's not much other than oil going in the cylinders. The other time is when the engine is off and the oil runs down the valve, starting with a good shot of oil on the valve to hit the combustion chamber at once. Little oil but at bad times for the plugs. The other way to tell is to look in the intake at the intake valves which of course means removing the intake if you don't have a scope.

It's either than or someone's been giving it a steady diet of Slick-50 and the rings are now gummed up/stuck, ... your call. Have a compression tester?

I suppose I could pick up a compression tester.....what should the values be for a healthy M103?

I am probably in denial....perhaps it does need a valve job. :o Is it hard to do? It doesn't sound like something I'd be comfortable tackling....

Can I hire you to do the seals? :D :D

I checked with the Department of Licensing and Regulation, ... I'm only licensed to work on my own cars ;~)

Besides, you'd have to haul away the rest of my 126 junk so there'd be room in the shop.

Not valves, just seals. Head and manifolds stay on for seals, usually in/out in a day but I can't say on the M103, have never done M-B valve seals (never owned an older gas one 'till now).

I'll do some further testing to see if its for sure the valve seals....I'll do the second gear accelerate and coast thing tomorrow to see if I get blue exhaust....

Tomorrow I am going to pull the plugs again to have a look and also I'm replacing the distributor cap/rotor/plastic shield....and I will test the wires for proper resistance.

If it does need valve seals then it may be headed to Betten! :eek:

Say Hello to the shop foreman, ... he's the guy with the 400E.

Yeah, I think he's the one who did the inspection on it when I brought it in last week. Is his name Don? He seems to always be the guy that works on the older cars.....

Do you know by chance what the ohm reading should be on the wires for a M103? :D

And....what is the "shop time" estimate for valve seals. (and should I have the guides done too if I end up doing that) Any idea?

The leads are copper so the resistance is close enough to zero, however the ends plugs (the plug ends) should be between 900 and 1100 ohms. If they are Beru then the ohmage is actually printed on them (at least they are on mine). The distributor cap also has built in resistance. Check this cap and the rotor and make sure they are good. Dissy caps are known to develop small cracks in them so clean it out well and do a very close inspection.

There is a DYI sticky on this forum that shows how to change out the valve seals. If you have upwards of 120,000 miles (180,000 km's plus) and then depending on the use of vehicle, the valve seals are in line for replacement. If the car has been left for long periods between runs the seals can dry out so (this can explain why M103 engines with relatively low mileage seals require replacing - previous owners include little old ladies who only drive the car to church on Sundays or once a month).

If you have upward of 160,000 miles on the engine it's time for a head pressure test. Possibly valve seals, stems and head gasket are due. Although this is a little expensive if you intend on keeping the car for a few years this would be money well spent.

Definitely VALVE SEALS!!!! Been there, done that!

This is from my service manual.
Model 124, test data for engine at normal operating temp

minimum compression pressure at (normal compression) approx 12 bar, (low compression) approx 7.5 bar.

Allowable difference between cylinders max 1.5 bar

ignition cable w/ spark plug connector 700-1300 ohm.

The compression test is a 1hour job on a 103. Once the plugs are all out, a remote-start switch in one hand, a rubber-ended compression gauge in the other, hold the rubber tip in each spark plug hole as you crank, quick and easy compared to the diesel version. Some things are actually easier with the gassers!

If you haven't already been following the thread, this: http://www.peachparts.com/shopforum/tech-help/241701-my-300te-head-gasket-thread-yes-pics.html one has a couple of nice photos of the M103 valve and rocker assembly.

Problem with doing the valve seals myself is that I have none of the following:

All special tools
Shop air supply (or any air supply)
confidence in doing it. :D


Anyways, today I re-gapped the plugs properly (my guess job was a bit off on most of them) None were really much dirtier than last time, so thats good...

Replaced distributor rotor and cap/cover, rotor was singed and scary looking, the cap was coroded and burnt, and the carbon tip was worn....only 2 of the tips measured properly on the ohm-meter! :eek:

I haven't started it yet, but I will be going out and doing so in a few minutes....I'll report back any improvement.

Well, it still ran with a miss/crappy. So out of frustration I slapped in the old champion resistor plugs that came in the car when I got it. Well what do you know, fires right up and runs smooth/powerful. No miss at all.

Explain that!!!

I just bought some el-cheapo "copper core classic" splitfire brand plugs....I am going to see how it runs on those......they were $1.29 each, I'm going to go gap them to .034" and throw them in and see how it runs.

Why does it seem to run better on the resistor plugs? Makes no sense.

Splitfire copper core
 

I'm afraid if you check www.splitfire.com Copper Core classic plugs are resistor plugs. Everybody says non resistor is the way to go. The dealership can provide them for less than platinums and you'll have the recommended plug in there. Also the exact proper heat range may be coming into play with other than recommended H9DCO.
I worked at a car parts store in the '80's when platinums came out and in Bosch plugs one platinum plug would replace up to 4 different heat ranges in the copper core. We had plenty of people bring platinums back because they wouldn't run right with the application being used.
Dan

ignition wires
 

Do you know by chance what the ohm reading should be on the wires for a M103? :D


the ignition wires are normally solid . the problem is at the plug connectors over a period of time the rubbber inside becomes conductive due to oil/water residues .The ignition will then develops a light miss and hesitation on acceleration.
when you remove the plugs look for a corona ring on the porcelin portion of the plug indicating a leaking plug connector. resistor type plugs compound the problem. use non resistor bosch HD 9c plugs

mak
300se 103

Well, it runs excellent on them, so I'm leavin' them in for now. The non resistor bosch plugs got all sooty and gross after barely 1500 miles and wouldn't run right even after I cleaned them off. (Sputtering and missing). Threw in these $1.30 apiece china plugs, and she's running awesome, and tons of power/rev's freely and smoothly. I'm a believer. So until it stops running smoothly, I'll be keeping them in it.

Oh, and it got 11mpg on the Bosch plugs on the last fillup. The mpg's continuously fell each fillup when using those plugs. Makes no sense.

The exhaust even smells normal/not oily or gassy with the splitfire plugs.

And I don't think it needs valve seals yet, it doesn't put out the slightest bit of blue exhaust, even if you rev it up in 2nd, coast, then hit the gas again....nothing. Oil consumption is less than a qt per 1000 miles.

M103s don't tend to smoke much during oil consumption from what I have seen. Don't judge anything by simply that. Mine doesn't, 260k and the head hasn't been rebuilt.

Keep the oil weight around 0/40 or 5/40. Plenty of film at high RPM and quick pressure on cold starts.

Have you pulled the old cap/rotor yet? They don't last that long as the M103 is a high rev car... just like the rest of the accys. With a poor arcing setup...

Do you have a lazy injector or many?

Do the stem seals to rule them out, under $20 and a few hours. Plus you get a new valve cover gasket and oil cap seal then to help idle vacuum. Also the upper timing cover always leaks, go ahead and replace the seals while it's apart, then toss on new cap/rotor.


Your PO sounds like a moron, so you get to basically replace everything and start fresh to get a solid base.

I'm going to wait till we build up some more $$ before I get the valve seals done....I'll get a quote tomorrow from the stealer on it. (I don't have the resources to do it myself)

It has a new: coil, rotor, cap, cap cover, and spark plugs. I've also changed the rubber tubing for the idle control valve, the valve itself, and the temperature sensors. This car has cost a fortune! :eek:

We'll see on the valve seals...if its not too expensive I'll just get it done right away so I don't keep fouling plugs....that'd be nice to not be pulling them on a bi-weekly basis! :D

As for oil, its currently on Mobil 1 0w40....think the turbodiesel truck 5w40 would work as well or better? Just curious....

You just need to rent a valve spring compressor and you can rotate the motor to TDC on each piston when you do them and put some string or something in there to support the valves.

OR justify this as a reason for a compressor. ;)

When I bought my 300SEL, I just replaced everything due to mileage. I had a decent amount of records and dealer stamps in the booklet (until about 190k) but from there was hit/miss until 221k. So about 30k of nothing.

1/4 of a million miles was enough, so I just resealed/cleaned/replaced anything related to the motor.

Is your O2 sensor cycling properly? Lambda set properly?

Mine is a California emissions setup car....(its from Nevada)....it has the diagnostic light and check engine light for the emissions system....if the O2 sensor was malfunctioning wouldn't that throw a code/light?

Depending what the dealer wants for the valve seals will decide if I get a compressor and do it myself.... :D Thats happened in the past...it might again.

The motor doesn't leak much, just a little bit by the timing cover. No idea on the Lambda....it gets about 20-21mpg....does that mean anything? :D

I think the Check Engine light is only for the O2 closed loop. Not familiar with CA emission gassers

Don't forget oil leaks are also vacuum leaks...

When's the last time you changed your spark plug wires? Why do I ask? :rolleyes:

My 300E performed like crap for months (after running great following a total top-end rebuild incl. head gasket). Plugs were fouled. Plugs replaced, and all was well for a few weeks. Pulled plugs again for re-inspection and they were once again fouled. Replaced plugs AND wires this time. Plugs stopped fouling, but I might add, that all of the excess carbon and fuel destroyed the O2 sensor, so I had to replace that as well.

Yeah they are not new.....I'll replace them at some point in the near future....they're $81 a set....so I was being cheap. This car isn't cheap. :eek:

I'm holding out to find a 300E in the junk yard with new wires on it. :D

Currently its running good, but if it fouls the plugs again quickly....wires/valve seals are on the list.

By the looks of those plugs......
 

I'd say the valve stem seals are leaking. Also as far as those plug wires go they can be replaced as a set or fabricated from bulk wire and oem wire ends. If you promise not to tell anyone, we can "lend" you the tools for both jobs.
Peace

... and Don should know, chances are he's done "a few".

I used to just replace the spark plugs on my M103 every 2 months or so. :D