STEVS
08-26-2014, 01:00 PM
Hello,
Just thought I would post this up on here, it can be useful for troubleshooting similar problems.
I recently purchased a 1997 C36 AMG and before I put it on the road I went about converting everything back to factory (previous owner had done some modifications) which included things like installing the factory grille, hood star, headlights and full factory Bose system (sounds much better than the giganto sub setup the previous owner had in it before). I also went about doing a full tune up, replacing all the fluids with factory specified types.
I bought the car with a stutter and a code showing a misfire. To shortly sum it up, the car had a serious lack of power, a rough stuttering idle (which results in jerking when you are waiting at stop lights) and if you try enter the high revs, which is where this motor really shines, specifically if you go WOT, it would trigger the check engine light, and turn off injector #4.
My trouble shooting process included checking/replacing the following, after reading up on similar problems on the internet, and speaking with some knowledgeable friends:
1. Engine wiring harness: This is a common known issue for these cars, but mostly affected earlier models. I did not think this was the culprit since I have seen affected harness, and this one looked like a revised version. Also some jiggle test, and light water spray helped with that confidence.
2. Coilpacks/Supressors: I started off by swapping the coil packs around, and actually tried a complete different set of coil packs/supressors. There was no change in anything.
3. O2 sensor: From all of the codes read, this was one of them, stating that it was the second 02 sensor, which my friend thought was strange as it does not have any role of controlling the air/fuel mix. The other codes were cylinder misfires, as well as intake air sensor, which is referring to the MAFs.
4. MAFs: This was one of the first things that came up on the search after typing in my exact symptoms. I felt that this would solve the problem. I started by cleaning the sensor first with a cleaner. I hopped in the car and it instantly felt better, the car drove great for about 20 min, then the engine light came back again. I purchased an original Bosch unit and installed it, the issue was still there, but I noticed that my idle had lowered to a more factory spec.
At this point I thought that it could be an ECU issue or there might be a need for reprogramming (a post from a member described that his exact issue was solved by a hook up to the STAR at mercedes. I did not see this being likely). One night my friends and I grabbed a multimeter and some wiring diagrams and had some fun. We checked all of the connections going from the ECU to the coil packs, the wiring to the MAFs, the voltage at the injector plugs and everything was perfect. We sprayed some water over the rail to see if there were any bad o-rings, nothing.
So from everything that was done, I thought the only thing left to try was a new ECU (very tough to find) or to swap out all the injectors (much easier). If you google 'leaking injector' you will see that a rough idle is a major symptom. One quick trip to the scrap yard with my friend and a stubborn stripped fuel rail bolt on my car later, and the new injectors were in and................hello powerrrr! Rock solid idle, smooth and full power. No engine light, no misfires, no limp mode. My guess it was either one or two bad injectors, but I just swapped in all 6 to be sure.
So hopefully this will shed some light on some people who are having similar issues. In the end a problem with a car can stem from anywhere, but sometimes the simplest and most evident things are the best place to start before you spend money on un-needed parts.
I have my power back. I am a happy camper!
Cheers!
Just thought I would post this up on here, it can be useful for troubleshooting similar problems.
I recently purchased a 1997 C36 AMG and before I put it on the road I went about converting everything back to factory (previous owner had done some modifications) which included things like installing the factory grille, hood star, headlights and full factory Bose system (sounds much better than the giganto sub setup the previous owner had in it before). I also went about doing a full tune up, replacing all the fluids with factory specified types.
I bought the car with a stutter and a code showing a misfire. To shortly sum it up, the car had a serious lack of power, a rough stuttering idle (which results in jerking when you are waiting at stop lights) and if you try enter the high revs, which is where this motor really shines, specifically if you go WOT, it would trigger the check engine light, and turn off injector #4.
My trouble shooting process included checking/replacing the following, after reading up on similar problems on the internet, and speaking with some knowledgeable friends:
1. Engine wiring harness: This is a common known issue for these cars, but mostly affected earlier models. I did not think this was the culprit since I have seen affected harness, and this one looked like a revised version. Also some jiggle test, and light water spray helped with that confidence.
2. Coilpacks/Supressors: I started off by swapping the coil packs around, and actually tried a complete different set of coil packs/supressors. There was no change in anything.
3. O2 sensor: From all of the codes read, this was one of them, stating that it was the second 02 sensor, which my friend thought was strange as it does not have any role of controlling the air/fuel mix. The other codes were cylinder misfires, as well as intake air sensor, which is referring to the MAFs.
4. MAFs: This was one of the first things that came up on the search after typing in my exact symptoms. I felt that this would solve the problem. I started by cleaning the sensor first with a cleaner. I hopped in the car and it instantly felt better, the car drove great for about 20 min, then the engine light came back again. I purchased an original Bosch unit and installed it, the issue was still there, but I noticed that my idle had lowered to a more factory spec.
At this point I thought that it could be an ECU issue or there might be a need for reprogramming (a post from a member described that his exact issue was solved by a hook up to the STAR at mercedes. I did not see this being likely). One night my friends and I grabbed a multimeter and some wiring diagrams and had some fun. We checked all of the connections going from the ECU to the coil packs, the wiring to the MAFs, the voltage at the injector plugs and everything was perfect. We sprayed some water over the rail to see if there were any bad o-rings, nothing.
So from everything that was done, I thought the only thing left to try was a new ECU (very tough to find) or to swap out all the injectors (much easier). If you google 'leaking injector' you will see that a rough idle is a major symptom. One quick trip to the scrap yard with my friend and a stubborn stripped fuel rail bolt on my car later, and the new injectors were in and................hello powerrrr! Rock solid idle, smooth and full power. No engine light, no misfires, no limp mode. My guess it was either one or two bad injectors, but I just swapped in all 6 to be sure.
So hopefully this will shed some light on some people who are having similar issues. In the end a problem with a car can stem from anywhere, but sometimes the simplest and most evident things are the best place to start before you spend money on un-needed parts.
I have my power back. I am a happy camper!
Cheers!