Have an '01 M5 w/@ 70,000 miles. Supersprint cat-back, power pulleys and K&N filters, among other non-engine mods. These mods have been on the car about 1 year+ and have had no issues other then on a rare occassion the yellow service engine light, which I have been told could be related to the exhaust. About 3 weeks ago, the car developed a severe hesitation when cold at around 2,000-2,500 rpm, to the point the car would buck or feel like it was going to stall until you got the revs up. Once you got above @ 2,500 rpm the car pulled strong as ever with no problems. In addition, once the car warms up, the problem at the lower rpm isn't nearly as bad, almost like a pause or the traction control kicking in (which it wasn't). Has anyone experienced this? Any ideas what it could be? It is currently with the dealer getting diagnosed again and the first read of the codes was indicating it was exhaust related (which I am not buying). They are going to do further tests to try and uncover the problem. Any help would be greatly appreciated.
first thing I would do is get it out of the dealer and to an indy mechanic. In my experience the dealer will always point to aftermarket stuff as a problem, they are part replacers, not diagnostitians. Plus they will drain your wallet faster than Uncle Sam! Get a peake code reader, and post what codes are found.
SM - I am having the same exact issue and I just got my fault codes cleared. I am leaning toward a problem with the MAFs???? I am not sure but I think the ones on my beast are the original ones that may have come with the car. Any info from other members would be appreciated...
check that fuel filter. i could be totally off base here but when the filter went bad on my E30 M3 it went bad fast and the problem was similar to what you're describing.
Have an '01 M5 w/@ 70,000 miles. Supersprint cat-back, power pulleys and K&N filters, among other non-engine mods. These mods have been on the car about 1 year+ and have had no issues other then on a rare occassion the yellow service engine light, which I have been told could be related to the exhaust. About 3 weeks ago, the car developed a severe hesitation when cold at around 2,000-2,500 rpm, to the point the car would buck or feel like it was going to stall until you got the revs up. Once you got above @ 2,500 rpm the car pulled strong as ever with no problems. In addition, once the car warms up, the problem at the lower rpm isn't nearly as bad, almost like a pause or the traction control kicking in (which it wasn't). Has anyone experienced this? Any ideas what it could be? It is currently with the dealer getting diagnosed again and the first read of the codes was indicating it was exhaust related (which I am not buying). They are going to do further tests to try and uncover the problem. Any help would be greatly appreciated.
smbimmer
I'm having the same issues and mine is also an '01 with 74,000 miles. Additionally, my car is completely stock. Thus no K&N issues. The car starts fine. Good steady idle. As I drive away it starts to run rough and buck at about 2000 RPM. Once I get 2-3 miles, the car runs great. No issues. The "seat of the pants" meter says it's not a MAF issue as the car pulls strong once it's driven 2-5 miles.
I just had a diagnostic check at my dealer and no issues were noted. It's almost as if the ECU can't quite figure out the current temperature and atmospheric pressure to meter the correct air/fuel mixture.
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That's my opinion, although I might not agree with it.
Initial thoughts are MAF's - have you recently cleaned and oiled your filters? The K&N's have a long history of clogging the MAF's with oil especially if over oiled. I would also look at O2 sensors and spark plugs.
__________________ Current Toys: 2000 M5 with lots of goodies, 1997 993 Targa mostly stock, 2002 Jeep GC all set for offroad, 2004 Acura TL bone stock
Have an '01 M5 w/@ 70,000 miles. Supersprint cat-back, power pulleys and K&N filters, among other non-engine mods. These mods have been on the car about 1 year+ and have had no issues other then on a rare occassion the yellow service engine light, which I have been told could be related to the exhaust. About 3 weeks ago, the car developed a severe hesitation when cold at around 2,000-2,500 rpm, to the point the car would buck or feel like it was going to stall until you got the revs up. Once you got above @ 2,500 rpm the car pulled strong as ever with no problems. In addition, once the car warms up, the problem at the lower rpm isn't nearly as bad, almost like a pause or the traction control kicking in (which it wasn't). Has anyone experienced this? Any ideas what it could be? It is currently with the dealer getting diagnosed again and the first read of the codes was indicating it was exhaust related (which I am not buying). They are going to do further tests to try and uncover the problem. Any help would be greatly appreciated.
smbimmer
My vote is for fuel filter as well. Especially with the mileage you have.
There are good threads on this board related to this. Do a search.
Also, you may need a reflash of your ECU. Was this done when you did the headers, etc.?
If not, it should be done asap. You are not taking full advantage of the better breathing.
An ECU reprogramming has a good history here of smoothing out a lot of cold start hesitation.
... Additionally, my car is completely stock. Thus no K&N issues. The car starts fine. Good steady idle. As I drive away it starts to run rough and buck at about 2000 RPM. Once I get 2-3 miles, the car runs great. No issues...
I'll chime in and make 3 of us.
When cold the car stumbles between 1000 and 2500 rpm. Once warmed up (about 3-5 minutes) mine still has a very slight version, but is really only noticeable in top gear at low speeds.
The only additional information I can provide on mine is that the problem only applies at partial throttle - if I bury it the issue goes away completely. It feels a lot like a manual choke motor with the choke in the wrong position.
Hopefully it goes away with MAF changes in a couple thousand miles, but I'm sure interested in everyone elses solutions!!!
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