Nursing a 190E back to health. a few bugs left.
 

So I acquired a 1992 190E 2.6 a little while ago. I am convinced that someone put oil in the cooling system, because it shows no signs of head gasket failure. I fixed the cooling system and I am very happy with the results. I just have one problem that I feel like is specific enough that someone might know the answer right of the bat.

Car starts a little hard when cold. If you push the gas it starts up quickly, otherwise it dies, then starts up on the second try. I don't think this is related to anything else. The real problem is this...

It runs very well while warming up. Once it gets up to temperature, sometimes it will start hesitating on takeoff and idling rough. I have pulled over, turned the car off, counted to 10, then started back up and it runs great for the duration of the drive. Also, it tends to work itself out after some highway driving.

This seems like a computer or sensor issue, rather than a physical problem to me, but I don't know where to start looking. Vacuum seems a little low (16hg), but everything vacuum operated works and the transmission shifts smooth.

Thanks everyone! I'm hoping to be able to drive this car 300 miles and back around christmas.

Back in the day when I had a 190E (I think we still used dial-up modems in those days, and a gallon of gas could be (sometimes) had for under a dollar)), the various pieces of vacuum hose on the idle air circuit had become brittle and needed replacing.

My guess would be OVP relay.. which can be re-soldered.. if its the problem.

Right, or at least check the OVP fuse, sometimes it's as easy as that.

Second guess would be the valve stem seals, have you looked at the plugs for deposits? Are you running the correct plugs?

Hey, thanks for all the suggestions. Turns out the issue isn't quite as predictable and is kind of random. Restarting usually temporarily gets it back to running right, but it still comes backs at random. I managed to get it home while the issue was happening. I tested the voltage at the battery: 13.4v, pretty good. Checked the vacuum. 11hg, not good. I restarted the car and it ran smooth and the vacuum was back up to 16hg. It is acting just like a car with a vacuum leak. I had the air filter off and didn't see and disconnected lines. Maybe I need to dig deeper?

I fiddled around with the OVP relay. it looks fairly new with 2 good fuses. I don't have any ABS lights either and my voltage is fine. I changed the plugs because it had bosch platinum 2s in it. I replaced them with bosch super plus 7978, which are what peach parts sells.

Maybe there is something to the idle air vacuum circuit thing.

Was the 13,4 volts while running?? If so it explains most of your problems, should be 14 volts with lights on.

if it makes any difference, the lights were on. is 13.4 really too low?

13.8 to 14.2 when running. Doubt it's the problem though. Could look at the brushes in the alternator, usually easy as replacing the voltage reg or if you want to lowbuck it you can replace the brushes if they are worn out.

I pulled the distributer cap. These was a little carbon on the contacts. I cleaned it a little bit and put it back on. Cold starting seems to have improved. I guess I'll see if the hesitation goes away. I'm ordering a new cap and rotor this weekend along with a fuel filter.

well, The car started hesitating again, but it takes way longer for it to start. I checked the trouble codes. There is nothing that can't be attributed to me tinkering with stuff. Intermittent problems are the worst. I guess we will see what the cap and rotor do when they show up. Cold starting is still bad. Even warm starting isn't much better. When it is running well though it barely feels like its even running.

I just figured out that when the poor running occurs, Running the car hard for a bit will clear it up. Reving the car in park does not though.

The cold start enhancements are in the "E" part of the CIS-E system, which is why they are difficult to cold start if the OVP misbehaves.

My experience with older cars with electronics is that connectors can be a problem that cause intermittent misbehavior. It just takes a little corrosion on these low voltage connectors to cause problems, which are usuallly intermittent.

My suggestion is to remove the big multi-pin connector from the ECU, give the pins and receptacles a good inspection with a magnifying glass. Dress off any corrosion with a sharp metal tool like an Xacto knife or dental scrapper. DO NOT USE ANY KIND OF SANDPAPER!

Once everything is clean give the connector a shot of WD-40 and reinstall it. No guarantee, but it's worked for me in the past. You should also inspect the other connectors associated with the ECU - like the various sensors on the engine that are part of the system.

About 15 years ago I had an infrequent intermittent engine stumble on my Cosworth Vega that has what is essentially a Bosch D-Jetronic EFI system with those miniature Bosch connectors. I systematically did the above process with all the connectors on the ECU, injectors, and sensors. I didn't find any obvious problems, but the hour I spent on the task was worthwhile. The problem has not reoccurred since.

Duke

Thanks! I will give all of that a try tomorrow.

I checked out all of the electrical connections. Inspected and resoldered the OVP and Tested the o2 sensor. Everything checks out. Something told me it would be a good idea to pull plug wires while it was running. Not sure why I thought it would be productive. The 2nd wire gave me a few light zaps. I was several inches away from the conductor holding on to the metal shield. The wires all tested fine resistance wise and look pretty good. Should I be getting wires for this thing? While testing the o2 sensor signal, I noticed that whenever there would be a slight rumble in the idle, the voltage would go up for a second. could this mean an injector problem or an ignition problem? The car always seems like it is getting plenty of fuel.

So I changed the cap and rotor. No change. I'm waiting for the adaptor so that I can check the fuel pressure. I tried driving with the o2 sensor unplugged to see if preventing closed loop solved the problem. This didn't change anything either. I periodically check and adjust the duty cycle (anti-tamper was already removed). It always seems to have a different reading every time I look a it. I'm suspecting a dripping injector for the hard starting, although I'm not too sure how to verify it. I'm kind of stumped here. It seems reliable enough even with this problem though. If anyone has any ideas I would appreciate the input. thank you.