Misfire and quasi-limp mode

[circuiticon]

I have a '97 M3 with bolt-ons and a tune.

In general, it runs fine. However, sometimes when I'm beating on the car and going WOT until redline, it will start missing immediately after an upshift, accompanied by a CEL. The CEL will generally read out to be misfires on multiple cylinders. The car will run really rough and weak (like it's not firing on all cylinders) until I clear the codes. As soon as the codes are cleared, it will purr like a kitten.

Has anyone experienced this before?

[flyfishvt]

What mods do you have? Who did the tune?

[circuiticon]

Engine Mods:
M50 Intake manifold
Intake
ASC delete
ebay headers
exhaust (no cat)
Tuned by Jordan @ RK Tunes

Note that the mods have been there since early this spring, and this is only a recent issue.

[QuinnClark]

I would start at the source of misfires, spark plugs,coil packs, injectors, fuel pump, ext. could be something little not working correctly under stress. If your fuel pump isnt as strong as it should be, it might work just driving around, and not work under full load. Analogy: if you have asthma, you dont have problems walking around, but you have problems after you break out into a full sprint.

[circuiticon]

So far I've tried the fuel pump, plugs, and coil pack boots.

But when you get a misfire, is it normal for it to go into a sort of "limp" mode once a MIL is set?

[circuiticon]

Injectors didn't help either.

[circuiticon]

Bump

[circuiticon]

When it goes into the "limp" mode, cylinder 5 isn't firing at all. If I uplug coil pack #5, it makes no change in how the engine runs.

[circuiticon]

Rebuilt the engine. Problem still exists.

[spyderg0d]

Lol, that sucks. Is check all the sensors while hey are hot. Use gloves or something yo keep from the heat. Is suggest at testing that coil pack. Crank sensor, cam sensor, get a readout on the mad and 02 done at a shop if you can.. Lastly, get a new updated or better tune. Check your bolt on mod. However, I would think one would have enough sense to do all his before rebuilding an engine... And how and what exactly did you rebuild?

[Eric93se]

How old are the cam and crank sensors?

[XnWarden]

Personally i think this sounds tune related

[circuiticon]

Lol, that sucks. Is check all the sensors while hey are hot. Use gloves or something yo keep from the heat.

Check what about them, exactly?

Is suggest at testing that coil pack.

Tried that, no dice.

And how and what exactly did you rebuild?

In a nutshell, I did new piston rings, bearings, seals, lifters, complete head rebuild, rod bolts, gaskets, etc. Spent a couple of grand just on parts.

- - - Updated - - -

How old are the cam and crank sensors?

No idea.

- - - Updated - - -

Personally i think this sounds tune related

I tried the stock tune to no avail.

[circuiticon]

So I had previously replaced the crank sensor with one from my spare engine to no avail.

I ordered a new sensor and sensor harness from rockauto and no more misfire!!! Problem solved?