High RPM Hesitation/Stumble

[RUddin3]

My 1998 3.2L M3 has a slight stumble (hesitation) at around 5500rpm and continues sporadically until redline. After all the research I've done, it seems to be the coil packs that are acting up. THe O2 sensors were replaced a few months ago, the coil packs are original, and the car is at 100,000 miles.

I'm still going to pull each one and check resistance on each one, but are there any other tests for me to use to check and be certain? Could it be anything else? The car runs absolutely fantastic except for the high-rpm stumble, which, from what I can surmise, shows itself only when the ambient temp is more than 60 degrees.

Have you guys any leads on a deal for new coil packs?

Thanks!

Drive Safely,
Raza

[klp110]

Hey,

I don't have an answer but I may have the same issue at 3-4000rpm. It's hard to describe but there is ever slight hesitation with incresing the throttle. Does this sound like your experience but at higher RPM. I have a 95 MS with 53K with the 3.0l engine

[RUddin3]

Hey,

I don't have an answer but I may have the same issue at 3-4000rpm. It's hard to describe but there is ever slight hesitation with incresing the throttle. Does this sound like your experience but at higher RPM. I have a 95 MS with 53K with the 3.0l engine

This sounds pretty similar to my experience and the hesitation is ever so slight, but apparent enough.

You might want to check your O2 sensors. I've read they helped people with the lower rpm stumble.

I looked at coilpack prices and they are not cheap. Hopefully I'll be able to find a deal somewhere.

Drive Safely,
Raza

[JClark]

I have a similar issue but its more like klp110's situation as its at around 3k. I'm pretty positive my stumble is caused by the knock sensors needing to be replaced.

[Modena NYC]

This sounds pretty similar to my experience and the hesitation is ever so slight, but apparent enough.

You might want to check your O2 sensors. I've read they helped people with the lower rpm stumble.

I looked at coilpack prices and they are not cheap. Hopefully I'll be able to find a deal somewhere.

Drive Safely,
Raza

Ruddin3, i have the same issue as you. It is higher rpm, only in 3rd and 4th and i would assume 5th if i stayed in it that long. Thing is, i really see it when the temperature DROPS. My take is that the car is leaning out with the intake and exhaust and i may need software to correct it. But the thing is that it used to happen when my car was STOCK! I've lived with it for two years, but i'd love to know what it is...

[RUddin3]

Ruddin3, i have the same issue as you. It is higher rpm, only in 3rd and 4th and i would assume 5th if i stayed in it that long. Thing is, i really see it when the temperature DROPS. My take is that the car is leaning out with the intake and exhaust and i may need software to correct it. But the thing is that it used to happen when my car was STOCK! I've lived with it for two years, but i'd love to know what it is...

That is interesting that it happened stock, especially with east coast gas (higher octane rating).

Interestingly enough, just lately it seemed to go away. I actually switched from Chevron to Shell gasoline and it seemed to have made the difference. Some others on the board (in CA at least) were suffering from my same problem and it seemed that Chevron was actually the cause of the problem. I think it is because most of our cars software was tuned on 92 and the cars are particularly sensitive with the 91. When I am at the race track, if I run 92 or 100 octane, I don't have the problem.

Regardless, when I do my plugs next, I'm going to try the colder, NGK plug that most of the track/autocross guys use. It seems that they had great success with them.

Drive Safely,
Raza