My fix for low RPM hesitation

[500kE30]

I searched on the forums to find the solution to my problem but never found a concrete answer. But today the problem has been fixed.

Problem:
At low RPM (less than 2k) while accelerating or under heavy load the engine would mis-fire (or hesitate). Despite this, the check engine light did not come on. (Eventually it did, but I had the problem for a long time before it actually illuminated)

Repairs that didn't fix the problem:
Fuel system cleaner
Spark plugs
Vanos seals
upper and lower intake boots

Final repair:
I installed 6 Bosch ignition coils (During diagnosis, I checked the resistance of all the coils but all of them checked out ok)

I hope this helps someone out there with the same problem.

[boostedthree]

Did you ever have your code read to determine if maybe you only needed one coil? I have the same hesitation which sometime happens as high as 2.5k rpm, but I don't think I will buy six coils at about $70 a pop. I still don't have any codes, so there is no way of knowing what might be needed.

[500kE30]

Did you ever have your code read to determine if maybe you only needed one coil? I have the same hesitation which sometime happens as high as 2.5k rpm, but I don't think I will buy six coils at about $70 a pop. I still don't have any codes, so there is no way of knowing what might be needed.

Long version (short version at the bottom)
After a long while of low RPM hesitation, the hesitation eventually occurred at all RPM and the check engine light came on. I used a generic scan tool to find DTC P0304 stored (cylinder 4 misfire). I turned the car off so that I could put the scan tool back, 3 minutes later I turned the car back on, the check engine light was off and the hesitation was only occurring at low RPM again. At this point I was convinced it was either a fuel injector or a coil. To confirm this, I swapped coils between cylinder 3 and 4, hoping to find out if the mis-fire would follow the coil or not. Many months later the check engine light did not come on until I had the car on the race track and it was misfiring at all RPM. The light went off and the all-RPM-misfire ceased before I could hook the vehicle up to a scan tool. The generic scan tool that I have is only able to read codes that are current, so by the light being out, I was not able to read any codes. I took the vehicle to Treehouse Racing and their scanner said I had mis-fires on all cylinders. Being frustrated with the problem, I bought 6 coils on the spot. Problem fixed.

Short version
Yes, it had a cylinder 4 mis-fire.

Pelican Parts sells coils for around $30 each you can replace all 6 in your driveway in 20 minutes or less. All you need is a small flat head screw driver and a 10mm deep socket ratchet to remove the engine cover. Very easy.

[boostedthree]

Did the hesitation cause the whole car to jerk like it was bogged down? My car is especially bad in fourth around 1.5k. This is the best example of the problem my car is having that I have found.

Can't autozone check coils? Maybe I will check them there before I buy anything. I don't want to drop too much money because the car has other problems that still need to be diagnosed.

[boostedthree]

Did the hesitation cause the whole car to jerk like it was bogged down? My car is especially bad in fourth around 1.5k. This is the best example of the problem my car is having that I have found.

Can't autozone check coils? Maybe I will check them there before I buy anything. I don't want to drop too much money because the car has other problems that still need to be diagnosed.

[500kE30]

Did the hesitation cause the whole car to jerk like it was bogged down? My car is especially bad in fourth around 1.5k. This is the best example of the problem my car is having that I have found.

Can't autozone check coils? Maybe I will check them there before I buy anything. I don't want to drop too much money because the car has other problems that still need to be diagnosed.

Yes, it did make the whole car jerk.

I don't know if autozone can/will check coils or not. All you need is a multimeter to check the resistance. Based on my experiece and the experience of one other person (who has checked many coild), you probably won't learn much, if anything, in regards to trying to solve your problem.

[1988 325ix]

If I'm not mistaken wasn't there a problem with ignition coils on e46s or was that just for the m3?

[500kE30]

If I'm not mistaken wasn't there a problem with ignition coils on e46s or was that just for the m3?

I believe that is true for vehicles equipped with Bremi coils. My car had Bosch coils installed.

[boostedthree]

So the Bosch coils were the ones that had issues on your car? What was wrong with Bremi?

[1988 325ix]

I believe that is true for vehicles equipped with Bremi coils. My car had Bosch coils installed.

Gotcha.

I have Bosch

[500kE30]

So the Bosch coils were the ones that had issues on your car? What was wrong with Bremi?

Yes and I don't know

[04 E46]

My car sounds similar to the other threads but idles fine and even slow acceleration is fine only when I accelerate harder does it jerk. Happens all gears above 2K RPM.

It sounds like the only way to find out if this is the problem is purchasing 6 coils. If the coils work properly at lower RPM and slow acceleration then the coils will probably test OK.

Thoughts?

[500kE30]

My car sounds similar to the other threads but idles fine and even slow acceleration is fine only when I accelerate harder does it jerk. Happens all gears above 2K RPM.

It sounds like the only way to find out if this is the problem is purchasing 6 coils. If the coils work properly at lower RPM and slow acceleration then the coils will probably test OK.

Thoughts?

Or you could buy one coil, and swap one at a time until you find the culprit.

[waveblaster]

After buying a used 2004 330CI and having the hesitation out of the gate, this post was a life saver. I had the car fully anaylized and nothing showed up but replacing the coils did the trick. I found them on line for $27 per for Bosch and it is was well worth it!!!

Thanks 500kE30!!

[rjsquire]

I'm about to order the coils, but man, this really goes against my intuition! The sudden drop in the power is so severe that it's hard to believe that it's due to one coil failure. I would have sworn there was something going on with the gas pedal.

Thanks for posting!

[hon2bmw]

Same issue when I bought my wagon, pulled codes even though I was not getting a CEL, misfire in Cylinder 1, switched that coil out with Cylinder 4, cleared codes, drove it a bit, came back, Misfire code followed the coil, replaced....

done,

hesitation, lugging, slugishness gone.

Luckily I had only replaced the plugs and air-filter up to that point.

[daytonatrbo]

I've been dealing with "soft" failures on coils for a while. My car never really hesitated, just cold idle shakes that usually went away, until they didn't one day.

[rjsquire]

Same issue when I bought my wagon, pulled codes even though I was not getting a CEL, misfire in Cylinder 1, switched that coil out with Cylinder 4, cleared codes, drove it a bit, came back, Misfire code followed the coil, replaced....

done,

hesitation, lugging, slugishness gone.

Luckily I had only replaced the plugs and air-filter up to that point.

Do you have a code reader? If so, which one? I've been thinking about buying one, and would like one that will pull all codes, even those that don't trigger the CEL.

Thanks

[mckazok]

I have had dropping rpm at cold starts, slight throttle lag and hesitation from time to time at moderate to heavy acceleration for months with no codea.
I always thought it was vanos seals but never got to fix it.
Finally yesterday, cylinder 2 stopped working, traced the misfire to ignition coil, replaced the same day.
Now there is no rpm drops, hesitation or lag, idles smoother, accelerates smoother.
Look like an old dying coil shows itself with different symptoms before it actually decides to give up.

Mine are also Bosch and even the bad one showed same resistance values with others.

[limberneck]

E39 528i M52TU
Just to thank 500KE30. I had the identical problem of hesitation at low speed under load, around 1200 rpm. Ran completely normally on motorways, fuel consumption normal. No CEL, no faults on my diagnostic software. No induction side leaks, cleaned the MAF, replaced all 6 sparkplugs - no effect. All 6 coils had same resistance of 5 ohms. Fault occurred even with MAF disconnected so I was leaning towards a coil problem but this thread was very helpful. I replaced all 6 coils - I really could not be bothered tracking down which one was faulty as the car has done 212k (miles). Cured the problem immediately. Oh - i bought Hella coils - just under 30 GBP each. Thanks again to 500KE30 - much appreciated.

[limberneck]

Apologies - that should be 0.5 ohms, not 5 ohms