'94 E320t Problems - Where Do I Start? - PeachParts Mercedes-Benz Forum

RobertFini · #1 05-02-2010, 12:17 AM

I am having some serious drivability problems with my "new" 1994 E320 tourenwagen and don't know where to start to get these things corrected. I violated my own prime directive when I bought this car: "There is nothing so expensive as a cheap Mercedes."

But it was so beautiful and in really good visual condition and it only had 137k miles on it, plus it has heated seats and I am a total sucker for heated seats. The previous owner had a receipt for a head gasket replacement at 124k, but very few other records. I bought this car to support my new business that takes me to racetracks and motorsports parks, and I've put 10k miles on it since I bought it about two months ago.

It starts right up when it's cold, but sometimes (not always) takes a lot of cranking to start when it's hot. The car has a really bad hesitation whenever I put my foot into the accelerator no matter whether the engine is hot or cold, chugging and sputtering and surging and sometimes backfiring. But when the revs build and I begin to back out of the throttle, it starts to pull like a freight train and runs like a scalded dog, definitely letting me feel the kinship with my C36AMG.

I am not getting a "Check Engine" light but I built one of those tester thingamajigs and downloaded the CS1000 Fault Code Scanner manual, and today I pulled codes from it as listed below, with my interpretations from the CS1000 manual listed in parentheses:

DM Code 5 (Exhaust gas recirculation faulty)
DM Code 6 (Idle speed control faulty)
DM Code 8 (Engine coolant temperature sensor open circuit)
DM Code 10 (Voltage at mass air sensor too high/low)
DM Code 16 (Closed throttle position information faulty)
DM Code 24 (Starter ring gear segments and/or crankshaft position sensor faulty)
Socket 6 (SRS/Airbag) Code 2 (SRS Control unit self test failure)
Socket 6 (SRS/Airbag) Code 8 (Voltage supply interrupted)
Socket 8 (HFM-SFI) Code 13 (O2S/Lambda control system operating at rich or lean limit)
Socket 14 (CC-ISC) Code 5 (Stop lamp switch)
Socket 14 (CC-ISC) Code 6 (Starter lock-out/backup lamp switch)
Socket 14 (CC-ISC) Code 14 (Closed throttle position contact switch)

With all these codes showing, I am mortified at the possibility that the engine wiring harness needs replacing, but a visual inspection reveals no cracking or flaking and I cannot find any cracked or broken vacuum lines in the engine compartment.

I would love to hear some suggestions on where to begin with diagnosing this can of worms.

jcyuhn · #2 05-02-2010, 12:02 PM

With all those DM codes, I am surprised you don't have more on pin 8. The first thing to do is clear everything and then see what comes back. You don't know how long these codes have been set, some may predate previoius repairs.

Next step is to determine the condition of the wiring harness. The collection of DM codes point toward an original, unreplaced wiring harness. The driveability issues are also typical of failing wiring harness.

The pin 8/code 13 could be vacuum leaks. But it could also be triggered by corrupted sensor inputs due to a bad wiring harness.

Use the search function to find old discussions on the 124 wiring harness, how to determine condition, etc.

RobertFini · #3 05-17-2010, 06:46 PM

Can someone tell me the procedure for clearing the codes on this car?

Chas H · #4 05-17-2010, 06:57 PM

You should determine the status of the engine wiring harness before you do anything else. Most likely it has not been changed, given your problems.

thauber · #5 05-17-2010, 07:51 PM

Quote:

Originally Posted by RobertFini

Can someone tell me the procedure for clearing the codes on this car?

For my M104 (93 300E) when using the make-it-yourself reader, after reading a code, wait for the flashes to stop then hold switch for 8 seconds and release. Then read next code and repeat. You don't need to wait to long after the code finishes flashing or you will have to try it again. After you have gone through all the codes this way and depending on the pin, you should get 1 flash saying that pin is clear. Look around a bit on the forum, but if yours is the 16 pin connector mine has, that way has always worked for me.

To check your wiring harness, cut back a small area of the outer wrapping near the MAF and the one running across your fuel rail. Inside should be nice colorful wires well insulated. If they are old looking, bend the spot you are looking at and make sure they don't crack. The old stuff will possibly fall apart in your fingers, depending on its condition. Mine was bad enough on the ETA that it was mostly corroded copper and dirt inside the outer wrap.

ji_mbenz · #6 05-18-2010, 02:38 AM

You might also look at the production date of the wiring harness by removing the battery and looking fo a tag on the wire harness in the vicinity of the OVP connection. The production date will be "Fertigungsdatum" (aka the "production" date) FYI - There may be two dates on the harness part number tag - the other date is the design date.

kiwi_bloke_nz · #7 05-18-2010, 06:05 AM

Could be wiring loom. Especially with all those codes and symptoms.

RobertFini · #8 05-19-2010, 11:17 PM

Thank you everyone for your input.

I just checked the date on the wiring harness and it says "03.04.02" so it appears to be a new one . Next step will be to clear the codes and see which ones come back.

In the mean time, any guesses as to what might be the problem?

latief · #9 05-20-2010, 12:42 AM

These might be the codes from when the harness was bad. but no one really cleared them. clear them first, and see what comes back...those will need to be addressed then....

macdrone · #10 05-20-2010, 06:06 AM

Remember throttle assembly has the same wires in it so check if it was changed, also see if lowering wiring harness was replaced.

RobertFini · #11 05-20-2010, 10:07 AM

So, this morning I cleared all the codes and drove to work; the trip is about 35 minutes, almost all highway. The climate control system recirculation light was blinking constantly and the system was not working - no fan and full hot out of the side vents. I also had the check engine light illuminated, which was not the case before.

I stopped for coffee at the 7-Eleven up the street from my office, and after restarting the car the climate control worked normally and the check engine light was no longer illuminated. The stumble is still there, but it feels a little better - wishful thinking, maybe. I'm going to drive the car for a couple of days before I go back and check for more codes.

With regard to the other wiring harnesses in the engine compartment, is it simply a visual inspection to determine if they're bad? I know there are some wires near the oil filter housing that are showing cracked and crumbling insulation - how far do I need to go with this?

latief · #12 05-20-2010, 10:20 AM

Just to be sure, cut a small bit of insulation in the channel the holds the wiring going into the coil area. that is the area most-likely to be affected if the wiring has not been changed. if you see crumbled wiring insulation inside, then you will need a new harness.

the smaller wires near the oil filter are for the lower wiring harness. not-essential to engine performance, and you could rebuild your own easily....

good luck !

daddi · #13 05-20-2010, 09:04 PM

HARNESS

RobertFini · #14 06-26-2010, 01:48 PM

Okay, so I finally got around to checking the new codes after clearing the old ones more than a month ago - good call latief!

The only codes that came back are #5 on the DM (EGR faulty) and #13 on pin 8 (O2 control system operating at rich or lean limit). So it looks like my problem is in the EGR system.

I'll do a forum search and see what turns up, but if anyone has any suggestions in the mean time let's hear them!

Best Regards,
Rob

RobertFini · #15 08-04-2010, 09:53 PM

I must give enormous credit to Arthur Dalton for helping me through this, with innumerable private posts back and forth - thank you for your patience, Arthur.

The old plugs were the proper Bosch F8DC4 units, and while they had obviously seen better days, they weren't in terrible shape so I cleaned, re-gapped and reinstalled them. The car ran very well, much better than before, but there was still a hesitation and surging under full throttle.

I had cleared all the codes and decided to ride it out for a while to see if any codes came back and whether the drivability improved. They did and it didn't, in fact the drivability deteriorated to the point where the car was chugging and missing and making me so disgusted that I must admit that I harbored thoughts of switching to a Toyota (not really, but almost) and continuously cursed myself for violating my own Prime Directive about nothing being as expensive as a cheap Mercedes, so I decided to try replacing the plugs as a "what could it hurt" step while I prepared myself for having to get deeper into this problem.

After a futile search for another set of the Bosch F8DC4 plugs, Arthur advised that some guys have had success with NGK BP5ES plugs, so I placed an order for a set down at my local NAPA and waited for them to arrive. Finally, they showed up and when I tried to install them, I found that they could not be installed because they require a 13/16" socket that won't fit down into the plug tube.

Drats - foiled again!

After some more research, Arthur forwarded to me a copy of the NGK part number decoder and we identified the part number for the 5/8" socket configuration: the BCP5ES.

Another wait while my local NAPA ordered the new ones, and when they finally arrived I gapped and installed them and it worked like you wouldn't believe! The car now runs like I knew it should, pulling like a freight train with nary a stumble or a cough all the way out to redline under full throttle. The kinship to my C36AMG is very clear, once again.

Who woulda thunk all it would take is a $12 set of plugs?!?

Thank you , Arthur!!!

Best Regards,
Rob