High rpm hesitation

[Doc Oc]

I am experiencing a sporadic issue that is starting to worry me. On a hard romp the car will hesitate a couple times between 7 and 8k rpm. Feels like a misfire problem I experienced in my last supra where the spark would blow out past 18 lbs of boost if the gap was too wide....however I put in new plugs at stock gaps in June and I am not FI. I thought maybe bad gas but I've been through 3 tanks, from 2 different shells. No codes. The only change I have made to the car recently is going from 5w40 to 5w50. Doubt that could be related but who knows? Anyone have any ideas?

[BPMSport]

Perhaps an intermittent coil, or fueling issue.

[Doc Oc]

Thanks. I did some more testing tonight and it doesn't happen in first and second at all but does in 3 and 4. Not sure if that is pertinent? Any way to trace down a dying coil?

[Rajmun340]

Originally Posted by Doc Oc

I am experiencing a sporadic issue that is starting to worry me. On a hard romp the car will hesitate a couple times between 7 and 8k rpm. Feels like a misfire problem I experienced in my last supra where the spark would blow out past 18 lbs of boost if the gap was too wide....however I put in new plugs at stock gaps in June and I am not FI. I thought maybe bad gas but I've been through 3 tanks, from 2 different shells. No codes. The only change I have made to the car recently is going from 5w40 to 5w50. Doubt that could be related but who knows? Anyone have any ideas?

I don't want to scare you better safe than sorry but long ago i had a similar problem in a different car. On the highway at high rpm the car developped those hesitations which are in fact intermittent short loss of power. It got worse until i almost got rammed by cars behind me, as the car would loose speed very quickly at highway speed due to aerodynamic forces and possible light seizing but recovers. very short hesitations turned to full seconds.

This is very dangerous as your rear brake lights will not turn on while your car looses speed like light to moderate braking. On the good side, if this is caused by RB spinning and recovering and your engine finally seizes a lawsuit like this would be undefendable by bmw and they would have to do sth about RBs.

[squartus]

Had this starting to happen in my truck, was coil packs going bad. Did have some loss of power when I romped on it in the M but that was from Spark plugs and cleared up soon as I changed them.

[Longboarder]

There is more load is the upper gears so that's why it can happen in 3rd/4th and you don't feel it in 1st/2nd. Any way you can get a data logger? Or maybe go to a dyno that can read your vitals?

[Leonardo629]

Pretty sure it it was engine related then the car would like crap at all RPMs.

[Doc Oc]

Originally Posted by Longboarder

There is more load is the upper gears so that's why it can happen in 3rd/4th and you don't feel it in 1st/2nd. Any way you can get a data logger? Or maybe go to a dyno that can read your vitals?

Good ideas....any suggestions on a data logger? Thanks

[Doc Oc]

Originally Posted by Leonardo629

Pretty sure it it was engine related then the car would like crap at all RPMs.

That's what I keep telling myself....really seems ignition/fuel related, but in the back of my head I keep thinking about ARP bolts and bore distortion.....and I'm sure I've read here that high rpm's also have an effect on bore round. However the hesitations are not happening in any predictable manner that would coincide with an engine stroke.

[Doc Oc]

If it matters when I changed plugs I used the ngk's, not BMW.

[Sales@Alekshop]

That is typical for a bad plug but it sounds like a bad coil or fuel delivery issue if you just recently replaced plugs. That RPM and gear is when the car is making max power and has the most load on the engine components.

[Longboarder]

Originally Posted by Doc Oc

Good ideas....any suggestions on a data logger? Thanks

Your tuner Evolve should have something for you. Also, I've heard that you could be asking for problems if you use any aftermarket plugs. I'm not an authority on that but others can chime in.

[Leonardo629]

Originally Posted by Doc Oc

If it matters when I changed plugs I used the ngk's, not BMW.

OE plugs are NGKs....you are fine.

[8600RPM]

Originally Posted by Sales@Alekshop

That is typical for a bad plug but it sounds like a bad coil or fuel delivery issue if you just recently replaced plugs. That RPM and gear is when the car is making max power and has the most load on the engine components.

Most load on engine is at peak torque, not redline. Peak fuel demand is at higher rpm and peak draw from coil and plugs. Therefore you probably realistically need to replace all coils as next step if no codes exist given you just changed plugs.

[Doc Oc]

Originally Posted by Sales@Alekshop

That is typical for a bad plug but it sounds like a bad coil or fuel delivery issue if you just recently replaced plugs. That RPM and gear is when the car is making max power and has the most load on the engine components.

Thanks. Think I'll pull the plugs over the weekend just to take a look....give me something to do while the wife's out of town. Anyone know a good source for coils? Ecs seems to be the cheapest but I'd love to find a whole set at a good price.

[squartus]

Yea NGKs are OEM, been running them for about 18k myself.

[Watersedge1234]

Just went through this myself - ECs has a good deal on a complete kit, coils and plugs. Best I found.

Originally Posted by Doc Oc

Thanks. Think I'll pull the plugs over the weekend just to take a look....give me something to do while the wife's out of town. Anyone know a good source for coils? Ecs seems to be the cheapest but I'd love to find a whole set at a good price.

[Doc Oc]

You are right, thanks, don't know how I missed it earlier. $700 bucks for the kit is good compared to everywhere else but I am still blown away that the coils are $85 each. Ridiculous compared to domestics and even Audi.

[///mawana]

I had this happen to my e46 and it was the fuel pump. It couldn't keep up with demands under high loads. A clogged fuel filter could potentially cause this too and I think, for the e9x m3, the fuel filter in integrated in the pump. Something to consider as well.

[dbyrd]

I had the exact same problem and it was a coil. No CEL but Benvo was able to remote in and identify the specific coil so I didn't have to replace them all. Try tuner or stealer or you could always replace them all.

[Weyne Masters]

I have trying to fix that since last October,unfortunately I haven't any success yet.
The same malfunction same RPM BAND but my car has S/C.

[Watersedge1234]

Hey Doc - just installed my new coil packs/plugs today and my hesitation issues disappeared. My car was stuttering and misfiring under high load, more so in higher gears. When I got in there I found the previous owner used Knockoff coils, definitely worth going OEM. Runs absolutely perfect now. No codes before the swap, I would definitely start there. Wouldn't worry about bore distortion, I doubt you'd experience hesitation due to bearings.

Originally Posted by Doc Oc

That's what I keep telling myself....really seems ignition/fuel related, but in the back of my head I keep thinking about ARP bolts and bore distortion.....and I'm sure I've read here that high rpm's also have an effect on bore round. However the hesitations are not happening in any predictable manner that would coincide with an engine stroke.