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I've got a strange issue with my '88 300CE that I've been trying to research and troubleshoot. On a cold start-up, acceleration is bogging down quite a bit. I can have the pedal to the floor and it will be crawling along at like 2500 rpm and not accelerating at all. I have to pump/feather the accelerator to get it up to the speed limit. After about 5-10 mintues of driving, everything goes back to normal: acceleration and shifting all working as expected.
I had a similar issue a year ago that I was able to fix. The engine would only rev up to 2000-3000 rpm after a cold start, but it would do so in neutral as well as in gear. I replaced the O2 sensor with a universal (Bosch) O2 sensor and this fixed that issue. This new issue is not entirely the same but it is very similar; a big thing I've noticed is that my gas mileage has not changed (was really poor when I had a bad O2 sensor).
Since the O2 sensor replacement, I've had the following issues that could be attributing to this new problem:
1) Transmission is leaking a bit, but I do my best to keep it topped off. However, without a full drain and refill it's not really possible to get the exact amount of ATF in. The level is within the operating range when I check it.
2) I had a fuel line leak (one of the smaller hoses that connects to the T-joint that connects the fuel tank to the fuel pump and filter). I had trouble finding the exact specifications but the internal diameter was the same as the original line I replaced.
I've seen a few possible suggestions that this could be the kickdown switch, kickdown solenoid, distributor or fuel pumps. Anyone have any experience with anything like this that was not driven by the O2 sensor? Or, is it possible that the replacement sensor has somehow already gone bad?
190E 2.6L 1989, 190E 2.6L 1988, BMW 535dXdrive 2014, BMW 428i 2015
(1) How does it idle right after cold start? Does it go into increased idle to about 1000rpm?
(2) How does it start cold? Should take no more than 1-2 seconds to start
(3) If you are driving with a cold engine you should never have to or want push full throttle, the closed loop emissions is not even operating yet
(4) For the first 3-4 minutes your O2 sensor is not even doing anything as you are in open loop mode, so it is not your O2 sensor
(5) Your cold running issues you have are probably due to the engine is not getting the fuel enrichment that is needed. The culprit for that could be ECU, coolant temp sensor, etc.
You should measure your EHA current during cold running and see if it more or less maps to the front part of this graph below.
Also do not overlook ignition components in case the issue is condensation in the distributor.
(1) How does it idle right after cold start? Does it go into increased idle to about 1000rpm?
(2) How does it start cold? Should take no more than 1-2 seconds to start
(3) If you are driving with a cold engine you should never have to or want push full throttle, the closed loop emissions is not even operating yet
(4) For the first 3-4 minutes your O2 sensor is not even doing anything as you are in open loop mode, so it is not your O2 sensor
(5) Your cold running issues you have are probably due to the engine is not getting the fuel enrichment that is needed. The culprit for that could be ECU, coolant temp sensor, etc.
You should measure your EHA current during cold running and see if it more or less maps to the front part of this graph below.
Also do not overlook ignition components in case the issue is condensation in the distributor.
It does take a few seconds to start and usually requires a bit of pumping the accelerator to get the engine to turn over. It idles at 1000 rpm.
I forgot to mention that it is worse (and takes longer to get running normally) the colder it is outside.
I've got a new distributor cap and rotor in the mail so will get that installed this weekend.
I'll have to test the EHA if the new distributor cap/rotor doesn't fix things. Thanks!
190E 2.6L 1989, 190E 2.6L 1988, BMW 535dXdrive 2014, BMW 428i 2015
Your issues point more in the direction of fuel enrichment. If the car does not start immediately your cold start valve is not functioning properly either.
For my car, when I strike the ignition even for a split the engine will start cold. I mean I can not stop is from starting, it is that quick. And it is not spring chicken at 210K miles.
And if your cold EHA enrichment is not happening, it is possible that there is an issue with your engine coolant sensor signal getting to your ECU.
Have you ever tested that. See if you can get that resistance first at the sensor followed by the same signal at the ECU side by unplugging it.
Make sure your keys are in your pocket when you unplug the ECU. You do not want your ignition to be on when you unplug it.
Have you measured your duty cycle when warm? Is everything normal there? oscillating around 50%?
'06 MB S55 AMG; '04 Audi Allroad 4.2; '05 BMW M3 Conv.; '92 MB 500E
Originally Posted by Philthedrill
I've got a strange issue with my '88 300CE that I've been trying to research and troubleshoot. On a cold start-up, acceleration is bogging down quite a bit. I can have the pedal to the floor and it will be crawling along at like 2500 rpm and not accelerating at all. I have to pump/feather the accelerator to get it up to the speed limit. After about 5-10 mintues of driving, everything goes back to normal: acceleration and shifting all working as expected.
I had a similar issue a year ago that I was able to fix. The engine would only rev up to 2000-3000 rpm after a cold start, but it would do so in neutral as well as in gear. I replaced the O2 sensor with a universal (Bosch) O2 sensor and this fixed that issue. This new issue is not entirely the same but it is very similar; a big thing I've noticed is that my gas mileage has not changed (was really poor when I had a bad O2 sensor).
Since the O2 sensor replacement, I've had the following issues that could be attributing to this new problem:
1) Transmission is leaking a bit, but I do my best to keep it topped off. However, without a full drain and refill it's not really possible to get the exact amount of ATF in. The level is within the operating range when I check it.
2) I had a fuel line leak (one of the smaller hoses that connects to the T-joint that connects the fuel tank to the fuel pump and filter). I had trouble finding the exact specifications but the internal diameter was the same as the original line I replaced.
I've seen a few possible suggestions that this could be the kickdown switch, kickdown solenoid, distributor or fuel pumps. Anyone have any experience with anything like this that was not driven by the O2 sensor? Or, is it possible that the replacement sensor has somehow already gone bad?
Have your caps and rotors been checked for moisture inside? If not, pop over to the 500E Board where most W124 owners congregate and diagnose these issues. Off rip that would be my guess.
190E 2.6L 1989, 190E 2.6L 1988, BMW 535dXdrive 2014, BMW 428i 2015
I should add that the graphic I attached above is for a M103 engine (2.6L and 3.0L versions). It maybe different for a 500E engine variety. Please take that into consideration going forward.
