335i Engine Hesitation between 2500 and 3000 rpm

I have a 335i (8/2007) production 6sp MT. I noticed a hesitation and roughness between 2500 and 3000 rpm under acceleration. There are no SES lights or any other symptoms. The car would accelerate through that range well enough but it was very annoying. It is particularly noticable in 4th through 6th gear. In 1st through 3rd gear the car accelerated too rapily through the rpm range to notice the roughness unless you are looking for it. My car has had the HPFP and all injectors replaced under recall and I paid for new spark plugs about a year ago and it currently has 67K miles on it. Otherwise the car is great.

I had the car scanned and there is a single code stored, (2AAF, Fuel Pump Plausibility). I took it to the dealer and they confirmed my symptoms (I did not tell them that I knew about the 2AAF and the TSB) and said I need a new low pressure fuel pump, the one in tank. I asked my service advisor if they were sure. "Why is it only in that rpm range?" He said the low pressure fuel pump is variable delivery and at that rpm delivery, that is the issue. I said OK but "fuel delivery at 2500-3000 rpm is different at each gear and varies with load on the engine." He said "we are sure that is the problem. I said "OK, do the repair." By the way, the BMW service bulletin says "do not replace low pressure components for 2AAF without testing a lot of other components first."

I picked up the car after paying my $700 and started driving it home. After warm up, I started accelerating and the car was still doing the exact same thing. I immediately brought the car back. The dealer has had the car seven days now and just told me today that they have opened a PUMA case with BMWNA.

I am reserving my opinion of this dealer until I have the problem resolved. Everyone can make a mistake. I will update the post as soon as I have resolution.

Has anyone experienced the same thing?

Your problem sounds to me like a problem I had with ignition coils. It was a misfire and most evident under heavy load in 3rd or 4th gear around 3k rpm. No codes until later, when the ignition coil went completely south.

I am also having the same problem with my car (2008 335xi 6MT). It happens only at lower RPMs as you stated. It feels like the boost is breaking up under moderate to hard acceleration. I too have had the HPFP and injectors replaced under the recall. Also, no check engine light and otherwise the car runs great. I haven't had a chance to bring it to bring it to the dealer yet and won't be able to for another week or so because I'm leaving for vacation Tuesday. Please keep us posted, I'd love to know the resolution to this issue.

Originally Posted by BimmerAWD

I am also having the same problem with my car (2008 335xi 6MT). It happens only at lower RPMs as you stated. It feels like the boost is breaking up under moderate to hard acceleration. I too have had the HPFP and injectors replaced under the recall. Also, no check engine light and otherwise the car runs great. I haven't had a chance to bring it to bring it to the dealer yet and won't be able to for another week or so because I'm leaving for vacation Tuesday. Please keep us posted, I'd love to know the resolution to this issue.

This is exactly what contaminated injectors and carbon buildup feel like. Shuddering at idle and stumbling idle are usually carbon buildup rather than injectors.

Originally Posted by Alpine300ZHP

This is exactly what contaminated injectors and carbon buildup feel like. Shuddering at idle and stumbling idle are usually carbon buildup rather than injectors.

Alpine, my car idles smooth as silk and runs great at all rpm. The only problem is the one I described on my post. The car even runs smooth at 2500-3000 rpm when cruising. It is only under load that I get the roughness.

Originally Posted by Alpine300ZHP

This is exactly what contaminated injectors and carbon buildup feel like. Shuddering at idle and stumbling idle are usually carbon buildup rather than injectors.

Sorry for the late reply, finally back from vacation. Alpine, I am experiencing very minor stumbling/shuddering at idle, but only when the car is cold. Once its warmed up, the stumbling/shuddering is nonexistent. This "boost break up" problem just started occurring recently for me (within the last 1-2k miles) and hasn't gotten any worse from initially noticing it. I'm only at 30K miles. The OP stated that his dealer told him that there was a turbo issue and now the car is running great. Another poster said a few bottles of injector cleaner got rid of his problem. I guess its time to bring her in and see what the dealer says, but due to all the replies while I was away, I feel slightly more confident in bringing it in and giving the dealer some options/opinions as to what the cause may be. I'll try and get her in by the end of the week and keep everyone posted on the diagnosis.

P.S. Thanks for all the insight everyone. Very much appreciated This is a great forum and I'm glad to be a member here and ONLY on this forum. Everyone here is very knowledgeable and helpful, especially compared to a certain other forum I once visited and never returned to

Originally Posted by BimmerAWD

Sorry for the late reply, finally back from vacation. Alpine, I am experiencing very minor stumbling/shuddering at idle, but only when the car is cold. Once its warmed up, the stumbling/shuddering is nonexistent. This "boost break up" problem just started occurring recently for me (within the last 1-2k miles) and hasn't gotten any worse from initially noticing it. I'm only at 30K miles. The OP stated that his dealer told him that there was a turbo issue and now the car is running great. Another poster said a few bottles of injector cleaner got rid of his problem. I guess its time to bring her in and see what the dealer says, but due to all the replies while I was away, I feel slightly more confident in bringing it in and giving the dealer some options/opinions as to what the cause may be. I'll try and get her in by the end of the week and keep everyone posted on the diagnosis.

P.S. Thanks for all the insight everyone. Very much appreciated This is a great forum and I'm glad to be a member here and ONLY on this forum. Everyone here is very knowledgeable and helpful, especially compared to a certain other forum I once visited and never returned to

My SA said that if it was studdering under light load (highway driving, idiling), then it most likely is caused by some carbon build up. She didn't even suggest I let them look at it. Only if it got worse (it has actually got better with Fuel Cleaner). With you car being so new, I would say that you take it to the dealer.

Originally Posted by Blubaron79

My SA said that if it was studdering under light load (highway driving, idiling), then it most likely is caused by some carbon build up. She didn't even suggest I let them look at it. Only if it got worse (it has actually got better with Fuel Cleaner). With you car being so new, I would say that you take it to the dealer.

Its not stuttering under normal highway cruising, only under moderate/harder acceleration when boost first begins to kick in and as I stated, only when the car is idling when cold. Thank you for your advice, I'll be bringing her in by the end of the week. Other than this minor issue, the car has run great, no other issues, and I could NOT be HAPPIER to be back in a BMW. I've missed them dearly since selling my E46.

Originally Posted by jburke4689

I had the car scanned and there is a single code stored, (2AAF, Fuel Pump Plausibility). I took it to the dealer and they confirmed my symptoms (I did not tell them that I knew about the 2AAF and the TSB) and said I need a new low pressure fuel pump, the one in tank. I asked my service advisor if they were sure. "Why is it only in that rpm range?" He said the low pressure fuel pump is variable delivery and at that rpm delivery, that is the issue. I said OK but "fuel delivery at 2500-3000 rpm is different at each gear and varies with load on the engine." He said "we are sure that is the problem. I said "OK, do the repair." By the way, the BMW service bulletin says "do not replace low pressure components for 2AAF without testing a lot of other components first."

Sooooo, was the LPFP replaced?

You should be aware that LPFP problems will cause HPFP self destruct over time. Very interested in final resolution! Could be as simple as a dirty filter....

Originally Posted by CALWATERBOY

Sooooo, was the LPFP replaced?

You should be aware that LPFP problems will cause HPFP self destruct over time. Very interested in final resolution! Could be as simple as a dirty filter....

Yes, The LPFP was replaced.

I just had an injector replaced last week. Now mine is also hesitating between 2500 and 3500 rpm under highway load acceleration. It won't do it in 1st or second gear when I'm pulling out.

Originally Posted by Blubaron79

I just had an injector replaced last week. Now mine is also hesitating between 2500 and 3500 rpm under highway load acceleration. It won't do it in 1st or second gear when I'm pulling out.

At the OP mileage I suspect that you guys have a combination of carbon buildup on the intake valves and some injector clogging. I have owned 3 N54 engines so I am somewhat of an armchair expert on this motor. I suggest you guys do the following:

1) Fill up with Shell 93 octane or Chevron 93 octane

2) Buy 4 bottles of BMW fuel system cleaner plus (just wait and let me finish)

3) At the first fill up do this: a) put a bottle of fuel system cleaner plus in before filling up the car b) warm up the engine at low RPM and speeds for 20 minutes c) take car onto the interstate and do 70 mph in 3rd gear making sure you are turning at least 4k RPM. d) Do the drive for 30 minutes and then shift to 6th and let the car cool down.

4) Two times a week for the next two-four weeks repeat number three making sure that you are running Shell or Chevron and using a bottle of fuel system cleaner in each tankful until all 4 bottles are gone.

I can almost guarantee your hesitation problems will be gone before or by the time all of the fuel system cleaner plus is used up. Once you have corrected the problem maintain the engine by doing my suggestion once a month. This is how I kept my N54's running good.....

Originally Posted by Alpine300ZHP

At the OP mileage I suspect that you guys have a combination of carbon buildup on the intake valves and some injector clogging. I have owned 3 N54 engines so I am somewhat of an armchair expert on this motor. I suggest you guys do the following:

1) Fill up with Shell 93 octane or Chevron 93 octane

2) Buy 4 bottles of BMW fuel system cleaner plus (just wait and let me finish)

3) At the first fill up do this: a) put a bottle of fuel system cleaner plus in before filling up the car b) warm up the engine at low RPM and speeds for 20 minutes c) take car onto the interstate and do 70 mph in 3rd gear making sure you are turning at least 4k RPM. d) Do the drive for 30 minutes and then shift to 6th and let the car cool down.

4) Two times a week for the next two-four weeks repeat number three making sure that you are running Shell or Chevron and using a bottle of fuel system cleaner in each tankful until all 4 bottles are gone.

I can almost guarantee your hesitation problems will be gone before or by the time all of the fuel system cleaner plus is used up. Once you have corrected the problem maintain the engine by doing my suggestion once a month. This is how I kept my N54's running good.....

Awesome! Thanks for the suggestion. Can I use any other type of fuel cleaner??? Or BMW fuel cleaner only?

I think I haven't used fuel cleaner enough in this car.

Originally Posted by Alpine300ZHP

At the OP mileage I suspect that you guys have a combination of carbon buildup on the intake valves and some injector clogging. I have owned 3 N54 engines so I am somewhat of an armchair expert on this motor. I suggest you guys do the following:

1) Fill up with Shell 93 octane or Chevron 93 octane

2) Buy 4 bottles of BMW fuel system cleaner plus (just wait and let me finish)

3) At the first fill up do this: a) put a bottle of fuel system cleaner plus in before filling up the car b) warm up the engine at low RPM and speeds for 20 minutes c) take car onto the interstate and do 70 mph in 3rd gear making sure you are turning at least 4k RPM. d) Do the drive for 30 minutes and then shift to 6th and let the car cool down.

4) Two times a week for the next two-four weeks repeat number three making sure that you are running Shell or Chevron and using a bottle of fuel system cleaner in each tankful until all 4 bottles are gone.

I can almost guarantee your hesitation problems will be gone before or by the time all of the fuel system cleaner plus is used up. Once you have corrected the problem maintain the engine by doing my suggestion once a month. This is how I kept my N54's running good.....

I did this yesterday and it really seems to have helped! It's not perfect yet, but from what I can tell its much better. I hope this is a decently long term solution.

I would also like more information about the BMW additive being different/better than Chevron's Techron. My SA really didn't know if it was any different.

Is there any definitive evidence that BMW's cleaner is better?

Anyway thanks for the advice, I drove 80mph in 4th gear (right around 4k rpms) for 30 mins.

I have a 2008 335i with 42,000 miles -- the HPFP and fuel injectors were replaced around 30k. Somewhere around 40k I started to experience the exact same symptoms that the OP described but on 5 different occasions over a 2 month period I also got the yellow check engine light with "limp" mode. Interestingly, the last three were while cruising at highway speed in 6th gear.

I took it to the dealer, described the symptoms and told them my best guess was carbon build-up. Called at the end of the day to say the car was ready. Based on the error code they replaced 2 hoses connected to the waste gate(s) because they were pinched and deemed "defective." Interesting that the OP's dealer also replaced a defective waste gate part, although not the same parts apparently. By the way, they did not see any evidence of carbon build up - not sure if they were blowing smoke or if they actually checked.

I can confirm that the car is running better but I still feel a very slight hesitation in the 2,500-3,000 range while accelerating in 5th or 6th gear. No yellow check engine lights or limp mode so far. I have run fuel treatment a couple times before the last dealer visit and noticed some modest improvement. I'll probably try it again soon with some high RPM runs for good measure. Hope this info helps.

Originally Posted by SAM67

I have a 2008 335i with 42,000 miles -- the HPFP and fuel injectors were replaced around 30k. Somewhere around 40k I started to experience the exact same symptoms that the OP described but on 5 different occasions over a 2 month period I also got the yellow check engine light with "limp" mode. Interestingly, the last three were while cruising at highway speed in 6th gear.

I took it to the dealer, described the symptoms and told them my best guess was carbon build-up. Called at the end of the day to say the car was ready. Based on the error code they replaced 2 hoses connected to the waste gate(s) because they were pinched and deemed "defective." Interesting that the OP's dealer also replaced a defective waste gate part, although not the same parts apparently. By the way, they did not see any evidence of carbon build up - not sure if they were blowing smoke or if they actually checked.

I can confirm that the car is running better but I still feel a very slight hesitation in the 2,500-3,000 range while accelerating in 5th or 6th gear. No yellow check engine lights or limp mode so far. I have run fuel treatment a couple times before the last dealer visit and noticed some modest improvement. I'll probably try it again soon with some high RPM runs for good measure. Hope this info helps.

SAM67. It wasn't the wastegate parts that fixed my problem. It was the O-Rings and clamps that connect the charge air hose (the one going to the intercooler) from the front turbo output. I'm glad they were able to fix yours too. It was driving me crazy.

Originally Posted by clspruiell

I did this yesterday and it really seems to have helped! It's not perfect yet, but from what I can tell its much better. I hope this is a decently long term solution.

I would also like more information about the BMW additive being different/better than Chevron's Techron. My SA really didn't know if it was any different.

Is there any definitive evidence that BMW's cleaner is better?

Anyway thanks for the advice, I drove 80mph in 4th gear (right around 4k rpms) for 30 mins.

The fact that you noticed an improvement after one high RPM run tells me that you have carbon buildup. As for the BMW fuel system cleaner plus vs. the auto store techron see what I wrote above. Mike Miller tells me the BMW stuff is of a stronger concentration, but no one really knows. The price spread is close so I would buy the BMW branded stuff myself.

Originally Posted by SAM67

I have a 2008 335i with 42,000 miles -- the HPFP and fuel injectors were replaced around 30k. Somewhere around 40k I started to experience the exact same symptoms that the OP described but on 5 different occasions over a 2 month period I also got the yellow check engine light with "limp" mode. Interestingly, the last three were while cruising at highway speed in 6th gear.

I took it to the dealer, described the symptoms and told them my best guess was carbon build-up. Called at the end of the day to say the car was ready. Based on the error code they replaced 2 hoses connected to the waste gate(s) because they were pinched and deemed "defective." Interesting that the OP's dealer also replaced a defective waste gate part, although not the same parts apparently. By the way, they did not see any evidence of carbon build up - not sure if they were blowing smoke or if they actually checked.

I can confirm that the car is running better but I still feel a very slight hesitation in the 2,500-3,000 range while accelerating in 5th or 6th gear. No yellow check engine lights or limp mode so far. I have run fuel treatment a couple times before the last dealer visit and noticed some modest improvement. I'll probably try it again soon with some high RPM runs for good measure. Hope this info helps.

I think you have carbon buildup and possibly injector buildup. Before you waste any more time with the dealer I suggest you do what I recommended in my first post and then go back to the dealer if that fails to help. At your mileage, carbon buildup is all but certain.

Originally Posted by Blubaron79

I just had an injector replaced last week. Now mine is also hesitating between 2500 and 3500 rpm under highway load acceleration. It won't do it in 1st or second gear when I'm pulling out.

Blubaron. It may be doing it in 1st and second but the engine pulls through that rpm range in less than 1 second making it hard it notice. It is much more noticeable in 4, 5 and 6 because it spends more time in that range.

I visited my dealer today and talked with the service manager. The car has been there 2 weeks. He told me that the regional engineer from BMW NA was there and they aren't sure what it is yet but are leaning toward the wastegate. I never had the rattling issue but wastegate sounds right to me based on the symptoms. Feels like the boost is dumping in that rpm range. I hope they do a goodwill repair. Even with the class action (wastegate warranty extended 1 year or 12,000 miles) I am screwed. I have 67k on mine. Hopefully they will take into account the fact that they replaced my low pressure fuel pump for $700 and that didn't fix it.

I stopped in last night to grab some fuel system cleaner. The SA said it was carbon build up if I only felt it under light engine load on the highway. She said to run 1 to 2 bottles of cleaner through it, and all should be good. The Westgate would be throwing a SES light, plus 2009 is when BMW started putting the upgraded Westgates on to get rid of any Westgate problems.

Originally Posted by Blubaron79

Awesome! Thanks for the suggestion. Can I use any other type of fuel cleaner??? Or BMW fuel cleaner only?

I think I haven't used fuel cleaner enough in this car.

Mike Miller tells me to stick with BMW fuel system cleaner plus so I trust what he says. There is apparently some difference from the BMW stuff and the Techron stuff you buy at the auto parts store. Given the nominal price difference (less than 3 bucks a bottle) I will buy the BMW stuff.

Originally Posted by jburke4689

Alpine, my car idles smooth as silk and runs great at all rpm. The only problem is the one I described on my post. The car even runs smooth at 2500-3000 rpm when cruising. It is only under load that I get the roughness.

Under load roughness and a smooth idle is, more than likely, injector buildup. I would still recommend you run 4 tankfuls of BMW fuel system cleaner plus even if you do not to the high RPM drive. I would still do the high RPM drive as it can only help and cannot hurt.

Originally Posted by jburke4689

I visited my dealer today and talked with the service manager. The car has been there 2 weeks. He told me that the regional engineer from BMW NA was there and they aren't sure what it is yet but are leaning toward the wastegate. I never had the rattling issue but wastegate sounds right to me based on the symptoms. Feels like the boost is dumping in that rpm range. I hope they do a goodwill repair. Even with the class action (wastegate warranty extended 1 year or 12,000 miles) I am screwed. I have 67k on mine. Hopefully they will take into account the fact that they replaced my low pressure fuel pump for $700 and that didn't fix it.

Maybe it is the wastegate, but before you pay them money to replace/fix the turbos why don't you try my suggestion. If my suggestion fails to improve the problem then consider wastegates. It is rare for wastegates to malfunction without codes and noise...

Originally Posted by Blubaron79

I stopped in last night to grab some fuel system cleaner. The SA said it was carbon build up if I only felt it under light engine load on the highway. She said to run 1 to 2 bottles of cleaner through it, and all should be good. The Westgate would be throwing a SES light, plus 2009 is when BMW started putting the upgraded Westgates on to get rid of any Westgate problems.

I agree with everything you said about the wastegates and it sounds like your S.A. basically told you to do what I did. Let me make sure you understand (as you S.A. seems not to understand) that on a direct injection motor as the N54 the fuel system cleaner plus will not clean the carbon buildup. If the fuel cleaner helps it is only because there was injector buildup (which is quite common on the pizeo injectors). The high RPM run is the only thing that will clean up carbon buildup on the valves (or an engine cleaning with walnut shell blaster for $500 bucks) because that is the only way to get the motor hot enough to start breaking the carbon down and blowing it out.....heat is what gets rid of the carbon....sustained high heat. Since we are not sure if the problem is one or both of these I recommend my dual approach which addresses both issues at the same time and is more effective than telling people to do each remedy separately.

Originally Posted by Alpine300ZHP

Let me make sure you understand (as you S.A. seems not to understand) that on a direct injection motor as the N54 the fuel system cleaner plus will not clean the carbon buildup. If the fuel cleaner helps it is only because there was injector buildup (which is quite common on the pizeo injectors). The high RPM run is the only thing that will clean up carbon buildup on the valves (or an engine cleaning with walnut shell blaster for $500 bucks) because that is the only way to get the motor hot enough to start breaking the carbon down and blowing it out.....heat is what gets rid of the carbon....sustained high heat. Since we are not sure if the problem is one or both of these I recommend my dual approach which addresses both issues at the same time and is more effective than telling people to do each remedy separately.

Water injection will clean cylinder carbon big time...all will be gone. Usually done with 50/50 methanol, of course. Put a smile on yer mug too.

There is doubt same will clean intake valves where PCV carryover gunks & clunks 'em. $600 dealer walnut shell blast there unless you DIY for dramatically less - a little solvent and a lot o'DIY PITA labor.

But...should be no carbon buildup in a stock motor!
.

Originally Posted by Alpine300ZHP

Mike Miller tells me to stick with BMW fuel system cleaner plus so I trust what he says. There is apparently some difference from the BMW stuff and the Techron stuff you buy at the auto parts store. Given the nominal price difference (less than 3 bucks a bottle) I will buy the BMW stuff.

Doesn't seem like BMW has much of a problem with Techron.



http://www.ebay.com/itm/BMW-Group-Fu...524ac8&vxp=mtr

Thanks. I'll be pushing the hard a little harder the next few tank fulls.

I met with my dealer today. I spoke with the service manager and shop foreman. Now they believe it is seals in the "turbo bypass." I can't find that in the parts list unless "turbo bypass" is the wastegate. The jury is still out on the dealer. We'll see. Both the foreman and service manager were courteous. Thats something. Three weeks and counting.