90 300D Power loss - Page 2 - PeachParts Mercedes-Benz Forum

2.5Turbo · #16 03-15-2007, 04:40 AM

Thanks for the replies!

Knew I forgot to list something. The air filter is fine. Turbo is good too. They tested the vacuum system and it's all holding over 20 inches of vacuum. Switchover valve is clear and functioning properly, bypassed to confirm. Built a code reader/clearer today, going to read and clear codes tomorrow. I know it's the EDS that is killing my boost, so I'm going to have to figure out what it's seeing (or maybe what it's not seeing) that it doesn't like.

I find it hard to believe that all three of these sensors went south on me all at once.

Just brainstorming here:

Could the EGR have become suddenly blocked by a chunk of carbon and triggered the airflow sensor code? I really don't want to have to replace it if I don't have to...it itsn't cheap.

The mechanic seems to think that the crank speed sensor and the rack position sensor codes might have been triggered due to the fact that there is no boost and the EDS is expecting that the engine should be turning faster and the rack opened further than it is? Previously he tried swapping the crank sensor out with a new one, but it threw the same code after he reset them, so he put the old one back. He also stated that in order to replace the rack position sensor if it's bad, the IP must come off and be opened up at another shop which is lots more $$$.

Quote:

You're right: Without a turbo, car isn't worth driving.

Exactly. Might as well go out and buy a 240D (no offense to those 240D drivers out there

) Adding that pressure controlled wastegate is sounding better and better

Monomer · #17 03-15-2007, 07:42 AM

I dont know if a stuck EGR would do anything, but be SURE that line isnt clogged or unplugged.

Pressure operated wastegate + boost controller + gage = fun.

Angel · #18 03-15-2007, 07:47 AM

240D owner here =)

One thing that struck me reading your post, and this may or may not help much - you say you have multiple sensors "failing".

In any other electrical system, I'd (at this point) begin to question the voltage supply - either on the wire to the device directly or system wide. Normally we wouldnt suspect alternators overvolt-relays (forget the MBZ name) or batteries, but I'd do some poking - messed up +12 wire somewhere ? consistent +12 to these (and other?) devices when running or when codes are thrown ? A Digital Storage O-scope hooked up to monitor voltages when driving would be the best way to verify this, but kinda tough to do.

Just throwing this out.

-John

pdrayton · #19 03-15-2007, 07:53 AM

I'm a 240D driver, but with 67 BHP you have to get used to not taking offense.

Anyway, my wife has a 1992 300D 2.5 (you can tell who's the boss huh!), and I've been hassling with a 5 code for months now (that's the y31/11 vacuum transducer error). I finally managed to figure it out and have it stay away just this past weekend by replacing the vacuum transducer. Took a while to figure it out though.

2.5Turbo, do you have the workshop manual part with the code diagnosis and repair instructions? It is pretty good. Doing anything without it would be pretty difficult. Let me know if you want me to email it to you.

Also, let us know what codes you get and if they come back after they've been cleared. Check if they take a little while to come back or if they come back immediately, ie clear the codes with the car off (except for 7 - engine speed sensor since the car is not running), and then crank it up and check the codes. If they are still not there, take the car for a drive and see if they come back (they probably do, but at least now you know they are new)

pdrayton · #20 03-15-2007, 07:56 AM

Good point Angel, about the overvoltage.

There is a 14V overvoltage protection fuse near the battery (behind the battery in the hidden compartment with those big electronic boxes I can never remember the name of). I've blown those before and had funny stuff happen - a/c do0esn't work, etc. Check those fuses - there's 2 of them i think.

BigBen · #21 03-15-2007, 03:09 PM

If you read my post here, I think you'll find we have a very similar story:

http://www.peachparts.com/shopforum/showthread.php?t=166429

I read in another post here (don't remember where though) that the EDS wiring harness can be a source of multiple error codes like we have. The same source mentionned this harness sells for about 200$, which wouldn't be that bad IF that was THE problem. I still have to figure out "from where to where" this harness goes...

I'll keep digging into it also. But I'm a very occasionnal mechanic, I started investigating this case one year ago now!

Good luck,

Bye,

asantoni · #22 03-15-2007, 08:56 PM

I have a 92 with the same problem. I installed a boost gauge and when everything is working properly it's a strong running car. The issue I am experiencing is interminent, car will run fine and then all the sudden there be no boost. Although I have not read any of the error codes, I know it's electrical because I can turn the car off and then back on while coasting on the highway and when I turn the ignition back on, turbo boost would come back to normal.

Just tonight I replaced all the vacuum lines. Most were in pretty bad shape and although the car would hold vacuum I suspect it was slowly bleeding off and throwing off the Mass Airflow sensor. I took the car for a 5 mile drive and turbo boost held throughtout the entire run. I will take it on a longer drive tomorrow before I pronounce it fixed. I have Garrett Turbo with an adjustable wastegate so if it's fixed I plan on bumping up the boost pressure to about 14 psi. Overall I can't complain about a car with 220,000 miles.

Good luck.

2.5Turbo · #23 03-15-2007, 08:57 PM

Did some digging today...think I narrowed it down a little.

Read codes. Got 2 (control rod travel sensor L7), 3 (air flow potentiometer B2/1), and 7 because the engine wasn't running. Cleared them all, still no boost. I drove about 30 miles around town (engine fully warmed up) today and it didn't set any codes while driving around. So all seems somewhat fine in computer world.

To test the turbo, wastegate and ALDA system, I disconnected the wastegate hose from the transducer and connected it to straight vacuum. Lightly drove it around being careful to not overboost too much, and the acceleration was there. So we can eliminate the possibility of a bad turbo, wastegate, or ALDA system, since they all worked when the wastegate was closed. Obviously I can't leave the wasegate closed all the time, since it would eventually lead to engine damage.

I also did a non-scientific audible test at the exhaust. Having someone rev the engine with the wastegate connected to the transducer like normal, no turbo spooling could be heard. With the wastegate closed with straight vacuum, the turbo spooling could be heard at the exhaust like when the car was accelerating to spec.

I'm thinking either it's the transducer or the wiring from the EDS to the transducer. Am I correct in assuming that all three Y31/x transducers are the same? Can I swap the wastegate transducer with say the EGR transducer and narrow it down? My transducers have the blue ring which are the old style that are noted in this service note: http://www.peachparts.com/shopforum/showpost.php?p=1395026&postcount=15

If changing those out and checking the wiring doesn't work, I really hope that the EDS hasn't taken a dump....

psfred · #24 03-15-2007, 10:10 PM

Check the transducers -- they split a diaphram and leak. Doesn't matter what signal the computer gives them, they do not provide vac to the servo (EGR, resonance tubes, or turbo wastegate). They should hold vacuum indefinitely at the supply line from the vac pump.

They are about $60 each, I think. Probably all bad, and that wil give you the errors as they do not activate the servos (no control rod movement, hence a no movement error).

Peter

2.5Turbo · #25 03-15-2007, 11:38 PM

That was it!!! Many thanks to all who replied...this forum is great! The transducer was bad. I swapped the Y31/3 wastegate transducer with the Y31/2 intake flap transducer, and the boost came back. Might be heading right over to MB tomorrow and getting one. Would buy from Phil but I kind of need it now before the GTG on Sunday. I bet the computer will eventually figure out that the flap is not closing and throw a code, but it didn't in the short drive that I took around the block. Do you think this would be a stocked item at the stealership?

And my indy told me the transducers were good...

pdrayton · #26 03-16-2007, 07:56 AM

Glad it's working for you.

I've been considering disabling the EGr. THat's makes the one transducer obsolete, as far as I know. Maybe you could do that? The transducers are about $160 at the stealership becuase they've been upgraded/modified. Old part # 0015407997, not sure what the new number is, but it is 2 different parts I think. I used a 0015407497 from a gasser and it is working too, so junkyards are an option if you want to keep the EGR going.

2.5Turbo · #27 03-16-2007, 12:21 PM

The computer would find out if the EGR wasn't working. I heard of somebody successfully disabling the EGR on a 2.5T, but I don't know how they did it. I drove around for about 20 minutes last night and it eventually figured out that the intake flap wasn't working due to the swapped transducer and cut boost. Restarting the car reset it. So I guess it's off to the stealership to spend some dough

I'll report back with the price this evening.

pdrayton · #28 03-16-2007, 01:28 PM

Rusty at the store on this site can get the transducer - you have to email him or put it in as a special order. Probably cheaper than from Merc.

Bio300TDTdriver · #29 03-17-2007, 02:01 PM

Do you mean Phil? Rusty is on another site.

Chris

BigBen · #30 03-17-2007, 04:49 PM

Quote:

Originally Posted by BigBen

I'll keep digging into it also.

So I got out today and plugged in a constant supply of vacuum to the wastegate actuator. And kept an eye on the boost gauge and WOW! There it went, flying like I've never seen this car go before. It seems everything was wrong since day 1 when I bought the car. Previous owner would not have sold it to me if he'd known about this. Too bad we were in snow storm today (12 inches of snow!), I had to be careful during test drive!

So I'll give a try to this method of testing the Vac transducers found here:

http://www.peachparts.com/shopforum/showpost.php?p=1395026&postcount=15

Then I'll try swapping Y31/1 (EGR Transducer) with Y31/5 (Wastegate transducer) and see how it goes.

I'll report my findings later.

Bye