CALL FOR HELP! '89 260E Intermittent Stumble / Check Engine Light; Codes? - PeachParts Mercedes-Benz Forum

ducaromeo500e · #1 08-22-2008, 01:39 PM

Let me start by saying I've read every stalling and hesitation thread on this site regarding w124s but the problems are so varied I feel I need direction.

My Mom's car, '89 260E has had an intermittent stumble with check engine light for a year. It will happen while she's running errands and then the stumble will just clear up and the light will go off. It has died on her once which leaves me concerned. The car has 199K and the only thing that doesn't work is the AC (saving that problem for later).

I've had the car all week and gave it a thorough once over looking for obvious stuff. I replaced a corroded negative battery lead (which I initially thought was the problem), idle control valve, and fuel filter. I've proceeded to put 300 miles on it this week with no problems! I gave it back to my Dad this morning triumphantly declaring that it's fixed; an hour later I get a phone call and he tells me he's sitting in the car staring at the check engine light and listening to the engine stumble!!

Being a Mech Engineer, I feel I'm qualified to fix the darn car if I can figure out the best way to proceed. I have an extra OVP relay, fuel pump relay, and ECU for this car but I don't want to swap anything unecessarily. Maybe the O2 sensor?

My other car is a 500E and I've successfully troublehooted all kinds of gremlins. I made the code reader on Jim F's site and it has been invaluable on that car. Will it work on this '89 260E? Is the code list the same? I need some direction! Please help me fix my nice Mom's car!

Thanks in advance,
Gregg

Arthur Dalton · #2 08-22-2008, 04:07 PM

If you have a spare OVP, then start there.......

ducaromeo500e · #3 08-22-2008, 04:44 PM

Will an intermittent OVP activate the check engine light?
The fact that the check engine light goes on while this is happening seems to be an important data point. Or will the light go on with a very low idle, while it is hesitating (it also illuminates at speed during the hesitation)?

I was also thinking of swapping the fuel pump relay. If I understand correctly, this model (1989) also has the mass air sensor relay bundled with the fuel pump relay?

Thanks for any input,
Gregg

deanyel · #4 08-22-2008, 04:48 PM

Your car may have an 8 pin diagnostic connector, would have for sure if it's a CA version, but it's a different pin size than on the 38 pin connector, and not the same code list. Code reading was quite primitive in that era.

Arthur Dalton · #5 08-22-2008, 04:51 PM

Change the OVP.

ducaromeo500e · #6 08-22-2008, 05:08 PM

I'll change the OVP tonight. I have a spare one with the double fuses. Then I'll give the car back to my Dad, because the problem only manifests while he's driving.

I downloaded the tutorial on checking codes for this model. However, the car was bought in Arizona and only has wires on pins 1, 6, and 7. So I don't think I can get any worthwhile info from the codes.

Thanks for the advice guys. If anyone has any other suggestions please chime in.

Gregg

deanyel · #7 08-22-2008, 05:31 PM

Pin 7 would be for the AC, pin 6 probably for the SRS. It looks like you don't have any engine code reading.

ducaromeo500e · #8 08-22-2008, 05:40 PM

That's how I understand it as well. Maybe I can get some clues as to why the AC is dead from one of the pins but that's for another day.

One a side note - when the car runs good (which is everytime I drive it, not my parents), it runs and drives so amazingly well for 199K, what a great chassis this is.

Gregg

ducaromeo500e · #9 08-22-2008, 10:54 PM

I put in my spare OVP............up goes the idle and "on" goes the ABS light. Looks like my spare is no good. Just for the heck of it I pulled it apart and sprayed it out with contact cleaner; fuses were good already. I put it back in and got the same result. So, the old one (single fuse) went back in and the car is running "fine" again.

If the original OVP in the car is bad, it is certainly displaying a different failure mode than the spare one that I tried.

I just got back from a 10 minute drive and it's running great as I expected. Tomorrow I'll drive it down to the local Pick N Pull and see if I can get another relay (they can't all be bad can they?). I'm planning on driving below the speed limit and keeping it under 3500rpm - just like my Mom would drive it!

She drives this car around with my 5 year old in the back

and I REALLY want to find the problem!

Thanks,
Gregg

Tims450SL · #10 08-23-2008, 10:58 AM

gregg, I have a 88 300E and I experience the same stumble at idle, then all of a sudden "POOF" its gone..no engine check light comes on, but I have a possible solution that most people over look....check the cat converter...sounds like it may need attention. Gets hot-clogs up...hope that gives a diff approach.

ducaromeo500e · #11 08-23-2008, 12:01 PM

Timothy, would it clear up without a restart? Sometimes it's happened at a traffic light, then she'll nurse it down the road and suddenly everything will be OK again.
Thanks for the ideas. Smog check is coming up in a couple of months and I've been wondering about the 199K cat.

Gregg

ducaromeo500e · #12 08-23-2008, 07:41 PM

For anyone that's interested

:

I swapped the ECU for another last night and gave it back to my Mom.
I had a chance to acquire a few more OVPs today just in case the ECU doesn't do the trick.

I talked to my Mom more about the failure mode. Always a check engine light accompanied by "chugging." Usually happens at idle but has happened while cruising under light throttle.

I'm starting to wonder about the hoses going to the idle control valve. If (when) the car malfunctions again I'll attempt another OVP swap and have a better look at the ICV hoses.

Gregg

Tims450SL · #13 08-23-2008, 10:03 PM

that is a basic challenge with a bad cat. mine is acting up, and ran to my midas muffler guy and he told me that the cat is a bad thing to get hot and clog up and effect the exhaust, and sometimes that makes the car idle poor, run bad, and stall. Mine is going in this week for a new one. tHEY ARE NOT CHEAP. :0(

Tims450SL · #14 08-25-2008, 06:33 PM

someone just told me that it is a coil issue-or a o2 sensor- I am locating them now...

ducaromeo500e · #15 08-26-2008, 12:53 AM

The car has been running good since I swapped the ECU. I am not convinced, but my Mom and Dad are very happy with it so far!
If it happens again the OVP relay is next to swap.
I must say, the car seems to have a more stable idle and feels a bit more peppy (as peppy as a 260E with 200K is going to feel) since I swapped the computer.

Fingers crossed.