Engine stutter (loss of power) between 4-4.5k rpm only

[rcfanatic]

Check the WOT switch in the TPS (electrically). If bad it will cause that.

Jim, would you mind elaborating on the mechanism by which a bad TPS could cause the symptoms that I'm seeing? The small rev range is what's confusing me

[jlevie]

Check the WOT switch in the TPS (electrically). If bad it will cause that.

[rcfanatic]

No one? Yesterday I checked the flap on the AFM to see if it was getting hung up in one spot but it moved smoothly

[rcfanatic]

Hope everyone had a fun thanksgiving!

So about a month ago I began noticing a stutter near and at WOT, between 4000-4500 rpm. It sounds like someone rolling an "r", and there is a loss of power that feels like fuel starvation or an ignition issue. When this occurs my AFR shoots up to around 17. After 4500 rpm it drops back to under 14 and accelerates normally again.

What's odd is that it only happens in this small rpm range, and is dependent upon load/throttle position and engine temp.

I have an m20b27 with 885 head, motronic 1.3 conversion, wide band o2. Cap/rotor, plugs, wires, fpr, coolant sensors, afm, fuel filter are all two years or less. Injectors were reconditioned about 3 years ago when I did the motronic 1.3 conversion. The TPS and CPS are also about 3 years old. I replaced the coil about a week ago but it had no effect on the problem. The car idles smoothly and accelerates smoothly aside from that narrow rev range.


Any ideas?

Thanks,
Adam