Misfires/Rough at 4200RPM (99 C43)
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99 C43
Misfires/Rough at 4200RPM (99 C43)
Hello all,
i'm the original owner of a 99 C43 which has spent the better part of 10 years just sitting (in a garage). currently 49k miles. i recently resurrected the car (oil, filters, new gas, new tires, trans/diff service etc.) and have been driving it around. i noticed the other day that while parked, if i run the RPMs up to about 4200-4300, the engine starts running rough, and i suppose is misfiring. i can kind of smell something different about the exhaust when this is happening. i've been a little worried about trying to get the RPMs up there while driving just cause i don't want something to go wrong while driving out on the highway.
i've put a bottle of techron in the latest tank on the off chance that the injectors are dirty. it's too early to tell if that did anything.
there are no codes stored in the computer.
looking at other posts here, it seems like MAS, spark plugs/coils or injectors are likely culprits. kind of in keeping with internal combustion engines in general lol.
is there anything special about 4200 RPM as far as how the fuel injection or spark works? meaning for instance do both plugs fire at all RPMS?
is there any way to isolate which cylinder(s) is/are causing this problem? changing all the plugs and all the coils seems like it would be pretty expensive. if the car eventually throws codes will it identify the cylinders?
i'm thinking of changing the MAS as that's relatively straightforward but i don't necessarily expect that to solve the problem. seems like after sitting so long that something in the fuel system seems a more likely culprit?
thanks, uli
i'm the original owner of a 99 C43 which has spent the better part of 10 years just sitting (in a garage). currently 49k miles. i recently resurrected the car (oil, filters, new gas, new tires, trans/diff service etc.) and have been driving it around. i noticed the other day that while parked, if i run the RPMs up to about 4200-4300, the engine starts running rough, and i suppose is misfiring. i can kind of smell something different about the exhaust when this is happening. i've been a little worried about trying to get the RPMs up there while driving just cause i don't want something to go wrong while driving out on the highway.
i've put a bottle of techron in the latest tank on the off chance that the injectors are dirty. it's too early to tell if that did anything.
there are no codes stored in the computer.
looking at other posts here, it seems like MAS, spark plugs/coils or injectors are likely culprits. kind of in keeping with internal combustion engines in general lol.
is there anything special about 4200 RPM as far as how the fuel injection or spark works? meaning for instance do both plugs fire at all RPMS?
is there any way to isolate which cylinder(s) is/are causing this problem? changing all the plugs and all the coils seems like it would be pretty expensive. if the car eventually throws codes will it identify the cylinders?
i'm thinking of changing the MAS as that's relatively straightforward but i don't necessarily expect that to solve the problem. seems like after sitting so long that something in the fuel system seems a more likely culprit?
thanks, uli
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12' W204 C63 AMG coupe "T-Rex", 12' W451 Smart Fortwo Pulse (99' W202 C43 AMG + Ultima Can-Am sold)
I suspect that if the engine runs rough at 4200-4300 rpm, you have reached the "safety" rpm limiter when in the 'P' position. I would strongly recommend you get the engine up to a good running temperature on the road and then slowly give it the beans. I'm sure you will rev easily pass the 4200-4300 rpm limit.
If it still runs rough, I would suggest you change the MAF sensor, but only for a OE or Bosch unit. It will be a bit more expensive than the cheaper knock-off items you can source on internet but those are just total garbage.
You did not mention sparkplugs in the service items done to the C43. Did you change them?
Keep us posted on your results
If it still runs rough, I would suggest you change the MAF sensor, but only for a OE or Bosch unit. It will be a bit more expensive than the cheaper knock-off items you can source on internet but those are just total garbage.
You did not mention sparkplugs in the service items done to the C43. Did you change them?
Keep us posted on your results
Last edited by DRBC43AMG; May 20, 2025 at 03:56 AM. Reason: completed
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From: Bolingbrook Illinois
1999 C43 Amg
I’ve owned 5 c43’s, each one had the same issue you are describing. Each car needed earthier a coil or a maf sensor. I
would start with buying a new good quality coil, take an old one from your car one at a time and swap with the new one.
After swap run the engine and see what happens. If it still runs rough move on the the other coil etc..
If that doesn’t work buy a new MAF sensor.
Btw, In my latest C43 I bought everything new to avoid problems later . It’s expensive but I knew eventually I would need to replace everything anyways so I just did it.
Hope you find the problem.
would start with buying a new good quality coil, take an old one from your car one at a time and swap with the new one.
After swap run the engine and see what happens. If it still runs rough move on the the other coil etc..
If that doesn’t work buy a new MAF sensor.
Btw, In my latest C43 I bought everything new to avoid problems later . It’s expensive but I knew eventually I would need to replace everything anyways so I just did it.
Hope you find the problem.
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99 C43
thanks for the replies, they are very helpful.
i did not replace the plugs. maybe at 50k and after so much time it would make sense to do that. when i remembered that there were 2 plugs per cylinder i figured that it was less likely to be a fouled plug, so i kind of discounted that in favor of other explanations.
i can't remember the car ever doing that in park (rev limit) but i'm getting old and might have easily forgotten. it does start to shake and stutter when it happens, would that be normal behavior for the rev limiter?
i did order a real MAF sensor from the arizona place but i've been having doubts as to whether or not that could be the problem. on the other hand the crankshaft position sensor died at around 45k miles so maybe these bosch electronics might just fail spontaneously.
yeah i guess that's the way to diagnose if it's a coil problem. i will give that a try. first i guess i'll test the rev limiter theory.
thanks for the help, i will investigate more and keep you posted.
I suspect that if the engine runs rough at 4200-4300 rpm, you have reached the "safety" rpm limiter when in the 'P' position. I would strongly recommend you get the engine up to a good running temperature on the road and then slowly give it the beans. I'm sure you will rev easily pass the 4200-4300 rpm limit.
If it still runs rough, I would suggest you change the MAF sensor, but only for a OE or Bosch unit. It will be a bit more expensive than the cheaper knock-off items you can source on internet but those are just total garbage.
You did not mention sparkplugs in the service items done to the C43. Did you change them?
Keep us posted on your results
If it still runs rough, I would suggest you change the MAF sensor, but only for a OE or Bosch unit. It will be a bit more expensive than the cheaper knock-off items you can source on internet but those are just total garbage.
You did not mention sparkplugs in the service items done to the C43. Did you change them?
Keep us posted on your results
i can't remember the car ever doing that in park (rev limit) but i'm getting old and might have easily forgotten. it does start to shake and stutter when it happens, would that be normal behavior for the rev limiter?
i did order a real MAF sensor from the arizona place but i've been having doubts as to whether or not that could be the problem. on the other hand the crankshaft position sensor died at around 45k miles so maybe these bosch electronics might just fail spontaneously.
I’ve owned 5 c43’s, each one had the same issue you are describing. Each car needed earthier a coil or a maf sensor. I
would start with buying a new good quality coil, take an old one from your car one at a time and swap with the new one.
After swap run the engine and see what happens. If it still runs rough move on the the other coil etc..
If that doesn’t work buy a new MAF sensor.
Btw, In my latest C43 I bought everything new to avoid problems later . It’s expensive but I knew eventually I would need to replace everything anyways so I just did it.
Hope you find the problem.
would start with buying a new good quality coil, take an old one from your car one at a time and swap with the new one.
After swap run the engine and see what happens. If it still runs rough move on the the other coil etc..
If that doesn’t work buy a new MAF sensor.
Btw, In my latest C43 I bought everything new to avoid problems later . It’s expensive but I knew eventually I would need to replace everything anyways so I just did it.
Hope you find the problem.
thanks for the help, i will investigate more and keep you posted.
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From: America
1999 C43 AMG, 2005 E55 Wagon
Have a sneaking suspicion it's just the rev limiter... Only happens while parked? It has a very hard limiter that makes the RPM's bounce like crazy at 4200 RPM.
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99 C43
hopefully it's normal. as mentioned it seemed like new behavior to me, but i don't drive the car regularly anymore so might have forgotten.
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99 C43
well, i guess i'm just stupid because it is apparently the rev limiter. got it up to 5500+ RPM on the freeway in 2nd gear with no problem.
i didn't expect that the rev limiter would work in such a way that the engine stutters and the car shakes, but i guess that's how it is. with all these EVs i tend to think in terms of fly by wire nowadays but if the gas pedal is actually mechanically connected to the throttle then i can see how this would happen.
i didn't expect that the rev limiter would work in such a way that the engine stutters and the car shakes, but i guess that's how it is. with all these EVs i tend to think in terms of fly by wire nowadays but if the gas pedal is actually mechanically connected to the throttle then i can see how this would happen.
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From: Land of mountains, cheese, chocolate and watches
12' W204 C63 AMG coupe "T-Rex", 12' W451 Smart Fortwo Pulse (99' W202 C43 AMG + Ultima Can-Am sold)
well, i guess i'm just stupid because it is apparently the rev limiter. got it up to 5500+ RPM on the freeway in 2nd gear with no problem.
i didn't expect that the rev limiter would work in such a way that the engine stutters and the car shakes, but i guess that's how it is. with all these EVs i tend to think in terms of fly by wire nowadays but if the gas pedal is actually mechanically connected to the throttle then i can see how this would happen.
i didn't expect that the rev limiter would work in such a way that the engine stutters and the car shakes, but i guess that's how it is. with all these EVs i tend to think in terms of fly by wire nowadays but if the gas pedal is actually mechanically connected to the throttle then i can see how this would happen.
Last edited by DRBC43AMG; May 23, 2025 at 05:03 AM.
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From: America
1999 C43 AMG, 2005 E55 Wagon
Glad to hear it's fine. Note that this is an M113 V8. They are idiotproof and bullet proof. If it runs for at least 1 minute and appears to be healthy, then it is completely healthy.
Don't baby it, go out and push that throttle to the floor and enjoy it. Unbreakable engines.
Don't baby it, go out and push that throttle to the floor and enjoy it. Unbreakable engines.
MBWorld Fanatic!
Joined: Mar 2010
Posts: 5,890
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From: Land of mountains, cheese, chocolate and watches
12' W204 C63 AMG coupe "T-Rex", 12' W451 Smart Fortwo Pulse (99' W202 C43 AMG + Ultima Can-Am sold)
Glad to hear it's fine. Note that this is an M113 V8. They are idiotproof and bullet proof. If it runs for at least 1 minute and appears to be healthy, then it is completely healthy.
Don't baby it, go out and push that throttle to the floor and enjoy it. Unbreakable engines.
Don't baby it, go out and push that throttle to the floor and enjoy it. Unbreakable engines.
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99 C43
i guess at this point the only question is if it is normal for the engine to stutter and shake when it hits the rev limiter.
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From: Land of mountains, cheese, chocolate and watches
12' W204 C63 AMG coupe "T-Rex", 12' W451 Smart Fortwo Pulse (99' W202 C43 AMG + Ultima Can-Am sold)
Also when you bounce off the rev limiter at WOT the engine will also stutter. However, I wouldn't do that too often as I can imagine it makes unnecessary stain to the engine components.
Last edited by DRBC43AMG; May 25, 2025 at 05:09 AM.
