Engine hesitation problem - The Unofficial BMW M5 Messageboard (m5board.com)

ArrestMeRed · 1st April 2005, 23:21

I've struggled with the engine missing for well over a year now. Initially, I thought it was related to the IATS relocation issue. It seemed that at idle, while sitting still, the idle would get very lumpy, everything would shake, and if I stabbed the throttle, it would sputter badly, go about 20 feet, then just as if someone hit a button, it would jump to its senses. I ordered the UFMotorsports kit, but never installed it because I decided I wanted the dealer to address the issue, and I didn't want to muddy the water with aftermarket stuff and risk them blaming the problem on me. I have already done the cold air intake reroute to the front bumpers.

The dealer has investigated this problem at least 6 times. Early on, the SES light came on, so that's what they went by. They replaced one MAF. The next time, they replaced both MAFs. Then they said they would replace the computer next. But they never saw any more codes. And I don't think they ever experienced the shuttering I was referring to. They kept asking me to make sure it wasn't my foot jerking back and forth on the accelerator, almost getting into a resonant frequency. That surely wasn't the issue, the frequency of misses was probably around 8 per second - much higher than if the car was lurching due to erratic gas pedal application by the driver.

The car almost always exhibits this issue after it's been warmed up, and then the engine has cooled so the variable rpm meter is at 4500. But sometimes, it does it when the engine is warm. Typically, it's around 1500-2000 rpm, but sometimes it's at 4000rpm. Never at higher rpms than 4000, doesn't affect full acceleration. For a few weeks, it was doing this every time I went out on my lunch break, and again after work. So I left the car with the dealer, told them to drive it in the morning to get it warm, then come back to it at lunch, making sure the rpm meter was at 4500. First day, they said it ran perfectly. Second day, I met them to observe. Same thing, no issues!! Third day, again, ran fine. The day I drove it home, it sputtered. I just can't capture the failure when the dealer is around.

The dealer has thrown their hands up in the air, and I don't necessarily blame them. All codes are showing perfect, time after time, and they haven't even witnessed the failure mode. They certainly believe me that there is a problem since I've been so adamant about it for so long. They just don't know what to do. I do a lot of stop/go driving, though the car always comes up to temperature. I've heard that the car adjusts to the driving conditions: M5s that frequently drive hi speed on the Autobahn may perform slightly different to our cars that don't see sustained high speed running. Maybe mine has fallen into a rut of slow speeds and traffic lights. I was hoping that maybe a day of flogging at the track might reset the computer. Nope - on the way home, it was doing it again.

Anyone else having this problem?? Any ideas are eagerly anticipated.

DIPLOMAT · 1st April 2005, 23:34

Tough one I would have said the MAFS. Have they checked your fuel pump? what about your accelerator cable? Have they looked at the Cam sensor? Spark plugs?
How many miles do you have?

mottati · 2nd April 2005, 01:01

i tried to rig up some air ducting a year or so ago, similar to yours i believe, and i kept getting ses mafs codes too. After a lot of trial and error, i gave up on that. I wonder if it has something to do with airflow and mafs data from the air intakes?
I never had the hesitation you speak of though...
Mike

edit: I have to add, if your dealer hasn't tried blaming your problem on you air ducting you've got a good one!

gsfent · 2nd April 2005, 01:41

Another stab in the dark, how about the ignition coils? If one is bad when it gets hot, it could show as an intermittant stumble. Not hard to check.
Regards,
Jerry

ArrestMeRed · 4th April 2005, 17:09

Quote:

Originally Posted by mottati

i tried to rig up some air ducting a year or so ago, similar to yours i believe, and i kept getting ses mafs codes too. After a lot of trial and error, i gave up on that. I wonder if it has something to do with airflow and mafs data from the air intakes?
I never had the hesitation you speak of though...
Mike

edit: I have to add, if your dealer hasn't tried blaming your problem on you air ducting you've got a good one!

That reminds me - I did one side of the intake first, the other side was still stock and I had to drive it before completing the job. The SES light did come on, I figured because of the variance in the air flow (which suggests that there IS a difference!). Once the job was completed, no issues. Seems like I had the problem before doing the job, too. And you're right - the dealer hasn't said squat about my mods.

I'm not sure what the dealer has checked. For all I know, they look for codes, and when they find none, the investigation is over. Lucky for me, the SES light came on again this weekend. So I'm going to schedule yet another visit to the dealer. Allegedly, BMWNA was in town one of the times I had my car in, and they got involved and didn't have any ideas.

Assuming they don't get it right again, how do I check the ignition coils?

I just rolled past 30K miles this weekend.

gsfent · 4th April 2005, 18:22

Quote:

Originally Posted by ArrestMeRed

Assuming they don't get it right again, how do I check the ignition coils?

I just rolled past 30K miles this weekend.

I assume the coils have a certain current or resistance spec when the engine is running. The dealer should be able to address that since there has to be a procedure other than engine codes to check to see if they are working. Bypass the SA and talk to one of the experienced techs. I doubt it will be a mystery to the tech. And they need to test when warm and then after the car has been run hard, or after you get your miss. They are under the valve covers, which are held on by 8 bolts IIRC. Let us know your progress. Good luck.
Regards,
Jerry

gdoan · 28th April 2005, 05:27

I had symptoms similar to what ArrestMeRed described. The car wasn't idling smoothly and seemed a little sluggish at times. I took my car in for service today. They told me it was a bad ignition coil.

They also discovered an oil leak around the oil pan gasket and are replacing it and performing an oil service. All should be under warranty as I only have 14,500 miles on it.

Greg
2003 ///M5 Jet Black/Black, Sport
Beastpower Sway Bar Brackets, Bluetooth, Aux Audio Input & all "plus" options except PDC

SC'dKellenersM5 · 28th April 2005, 05:31

with the master tech looking at it and it hooked to the Gt1 at the shop, i dont see why they cant find out what is wrong. EVERY engine parameter is measured by the car and shown on the GT1 so its very hard for me to think that they can not find out what is causing this.

Sharif · 28th April 2005, 06:52

My car does the same thing, especially when the car is cold. They put new ignition coils etc. no change.

Tonight the car stalled and would not start again. I have a feeling it's the fuel pump...

DavidS · 28th April 2005, 11:49

Do you have any misfire fault codes stored in the DME (ECU)?

My suggestions:

1. Drive the fule tank almost empty, then add two bottles of strong Injector Cleaner and a gallon of petrol. Drive the engine really warm (oil temp at 90 deg C) at high revs, and much WOT accelerations.

If it helped, fine, else:

2. Check condition of spark plugs.

3. Check compression.

4. Check fuel pressure.

5. Check ignition coils.

David