'88 W124 260E stalls when warm

[El Caballo]

My 1988 260E runs fine when it is cold, but only after a few minutes it starts to stumble, shudder and tries to stall under load. The ABS light comes on and given all of the other posts on the subject, one would suppose that it was the OVP. I thought so as well and am now $132 poorer as it didn't fix a damn thing. I won't gripe about having the new one anyhow because the old one literally came apart as I removed it, I just wished it worked as the fix is all.

So, that leads me to think that there must be some sort of temperature related part that is making the computer believe the car is too hot. Whatever the computer believes, it's running like it has one shoe nailed to the floor.

Again, cold runs fine, warmed up wants to die. I stopped it one time and turned the engine off, tried to restart it and had to give it a go three times before it caught. High revs will keep it alive, like over 2,000rpm which is useless at a stoplight.

Your help is greatly appreciated.

 

[219]

I've had the same with various M103 2.6 and 3.0 litre and M104 300-24 engined cars .

They are not so 'clever' as to be fitted with a computer .

Usually it is something basic like a cracked distributor cap or just needing a new set of spark plugs .

 

[Benzowner]

As above, with none of the computer problems, you have to revert to basics. Check the HT leads, plugs, distributorcap, rotor, fuel filters etc.

 

[grober]

If your car has the early Jetronic K injection system your problem is almost certainly the Warmup Regulator which has a direct effect on mixture control pressure. Its an electromechanical device with lots of diaphrams bimetal strips and springs to go wrong. Its normally found bolted to the front of the cylinder head.

see http://mercedes-190.co.uk/topic/219465/1/#new look for warmup regulator

 

[El Caballo]

So what is the OVP attached to? I was sure I was looking at a computer. Thanks for the schooling, I guess I was making it harder by half then.

Semantics question: what is an HT lead? I need an American translation.

 

[219]

HT leads are High Tension leads - from the distributor cap to the spark plugs and from the coil to the cap .

As Graeme says the warmup regulator is a distinct possibility , however I have had those exact symptoms with every one of the half dozen cars I have owned with those engines and it has always been either the plugs or the cap .

All the other suggestions above are valid too .

You may well have had a problem with the OVP causing low voltage and bringing on the ABS light , however not connected to the warm running issue .

 

[grober]

The OVP powers the ABS unit and the fast idle regulation and engine ECU. One symptom of OVP problems is that the abs light comes on simply because its supply voltage is too low- there isn't anything wrong with the unit itself just its supply. The fast idle regulator is a motorised unit which opens and closes the throttle bypass to assist idling when cold or when extra loads are imposed on the engine such as air con etc. Again an OVP fault might cause that to malfunction-- however early systems had a more primitive bimetal strip based unit. Without seeing the car its difficult to know what injection system you have.

HT lead= high tension lead= sparkplug or coil leads

Derek beat me to it.

 

[El Caballo]

Thank you, I will try to post a picture of the engine bay tonight.

 

[stwat]

The fuel pump relay is also worth a check.

 

[El Caballo]

Is it next to the fuel filter?

 

[219]

Can't remember on the 124 , but the FPR will either be behind the battery , or near the fusebox ; it's the one about the size of a 20 pack of cigarettes and usually has 'kickdown' printed on top .

 

[grober]

Thank you, I will try to post a picture of the engine bay tonight.

Try to remove the the air filter first before you take a photo. Then take a photo from the fuel injection side of the engine. There's little to be learned from the exhaust side.

 

[SHAKTER]

I had the exact same issue with my 1990 300CE (albeit without the ABS light coming on). Its a common issue.

There was moisture build up in the dizzy cap - had that cleaned out and sealed properly. Put a set of new leads in and now running smoother than ever.

Under load however I do get a very minor drop in voltage (eg, can see headlight power fall intermittently) so guessing that could be linked to the OVP - I may as well get that checked out. Could just be a fuse so a relatively easy fix.

As all the posts above, get your dizzy cap and leads looked at - hopefully all will be well.

Regards.

 

[El Caballo]

I'd like to thank Graeme, Derek, and Geoff for the reminder to go back to the basics.

As it happened, the distibutor cap was the culprit and it was in one word, appalling. All of the conductors inside the cap were so corroded that there was no way I could even clean them up as a temporary fix. I made a solution of bicarb and water and it removed the corrosion alright, but there really wasn't anything left. The little bobbin inside in the center of the cap for the coil lead was non-existent. I can only imagine that this cap had been in there for ages. Funny thing is, or not so funny, there are receipts for a cap and rotor and a tuneup shortly before I bought the car.

I have to say that the way the car performed up until very recently is a tribute to the way these cars are designed and built. The fact that it even ran at all is surprising to me. It ran so smoothly that those ignition pieces didn't pop up as the first place to go when the problems did show. Lesson learned.

BTW, yes I replaced the rotor as well, and threw in a new set of plugs to boot. Now it runs flawlessly.

 

[grober]

Glad you got it sorted. I had assumed [wrongly!] you had checked all the basics. On older cars the first port of call is always the HT circuits followed by the low tension side followed by fuel supply. the "basics" as Geoff2 pointed out. RESULT!