1992 500sel gauge issue and missfire - PeachParts Mercedes-Benz Forum

rwd4evr · #1 03-21-2017, 06:44 AM

I got a 500sel not too long ago partially disassembled. the guy said the fan clutch was bad. reassembled it with a good one guess what? Not the issue. It would start and immediatly stall, i could get it to keep sputtering but no point. had no operable gauges either. the engine injector harness was original and total garbage. found a used one 2014 delphi build date. I installed it tonight and now it will idle but pretty rough. I cleaned the distributor caps and rotors with my dremel and a brass wire wheel but they are pretty pitted. it seems to clear out when you rev it up but its got some thing strange going on with the asr. when the engine is revved sometimes you can hear it change tone and in order to keep it running you have to give it a lot of throttle to the point where the mechanical throttle overtakes the asr actuator, then it will stall when released and the asr light is on on the dash. All of this time even with the new harness i have no gauges working(including speedo and tach) except temp, but there are no warning lights while its running and its illuminated perfectly. The majority or all of the warning lights work when first turning the key to on. i took it for a short spin down the road and i have a vacuum issue with the brakes for sure, they only feel right after the engine gets a pretty good rev. fonzi had the thought that the brake booster could be leaking and causing a big vacuum leak and the terrible idle, but its still got other issues for sure. it seems to wake up and have most of its power over a certain rpm/ throttle position. ive checked all the fuses, it is charging fine, 14.3 Volts. gonna check the booster for leaks but im clueless on the gauge thing.

rwd4evr · #2 03-22-2017, 11:46 AM

UPDATE. We tried adjusting the throttle cable to bring the idle up but all it did was trigger the ASR light and when that is on it won't stay running. When I pass my hand over the mass airflow sensor not sealing it or anything, it drastically changes idle. So I disconnected the plug on the MAF and the idle smoothed out. So I'm guessing the MAF is bad? I am also able to wiggle the MAF A little bit, that's not correct right? None of this is doing anything for the gauges(not that I expected it to). Anybody have any ideas?

Junkyarddawg · #3 03-22-2017, 01:39 PM

The car really should be scanned with HHT or impulse counter so you can document the codes, try to erase them, then see whats coming back. I can tell you from experience that the hot wire MAF sensors on those cars are extremely sensitive and require laminar flow to operate as designed, this means that all testing and operation should be performed with the air filter housing installed or you will be chasing your tail, wondering whats going on. Some of the more common issues are the dist caps, rotors, suppressors, wire ends and coils. I would do a compression test and check the fuel pressure and volume before I started making rocket science out of it. Make sure you check all the fuses in the control module box, base module, and be sure the engine to chassis ground straps are clean and tight.
Best regards

rwd4evr · #4 03-22-2017, 02:55 PM

OK. So I checked all the fuses in the coffin box. All the fuses in the box by the brake master and all the fuses in the trunk. Am I missing any? As far as codes go. When it's running I have no warning lights on unless I mess with the throttle from under the hood then the ASR goes off and idle drops and it stalls. It's a 1992 so no obd2 that I'm.kinda familiar with, so I'm guessing the code reading is a Mercedes only deal? I don't know anything about HHT or impulse counter. I'll have to check the ground strap. I did run it with a timing light on all the wires and it seemed consistent. Cleaned the caps and rotors but they are rough looking. Haven't pulled the plugs either but it sure sounds healthy when it's revved up. What about the gauges? Could it be the cluster or a plug disconnected? It has function on the lights and temp but no other gauges.

Rick76 · #5 03-22-2017, 03:31 PM

The impulse counter is a self-made tool. All you need is an LED, a resistor for current limiting to the LED, a switch and a couple of wires. Plans are on this forum and all over the internet.

rwd4evr · #6 03-22-2017, 03:36 PM

Cool. Thank you.