Help!! Stumble/Cut at 5000 RPM

[Purplehazedog]

Okay guys, need your help. I missed my SPEC E30 race on Sunday because I could not get my car to run.

Here's the problem:
My car would Stumble/Spudder at 5000 rpm. I could not get it to REV past 5K.
This is the second time this has happend and both times the car will run fine on Saturday, but Saturday night and Sunday its starts the madness!

My Crank Sencer was Frayed From the belt, When I replaced it with a good one (From a donor car) My car would just cut out at 5000. It is a sudden cut of power. I was able to race when it was spuddering at least, but I was stuck in last place.

Here is what I replaced to try and fix the problem:
Coil
Cap
Rotor
Fuel pump
Fuel filter
plugs
Plug wires
ECU
tested Battery
AFM
Air Filter
Adjusted valve lash

I have no Idea what to try next, Has this happend to anyone else? What do I do next?

Thanks!!

[jlevie]

Check the WOT switch in the TPS. If it is bad performance will be badly down above 5000rpm.

[Purplehazedog]

I will check that today, Thank you

[603Racing]

Jim's probably right. Sounds like a fueling issue (running lean), probably due to the TB not sending the proper signal to the ECU.

[Gregs///M]

When you replaced the AFM, did you replace it with another used one? Or a rebuilt one? Cutting out at specific RPM is a symptom of bad AFM.

[jlevie]

When you replaced the AFM, did you replace it with another used one? Or a rebuilt one? Cutting out at specific RPM is a symptom of bad AFM.

That is true below ~4500rpm. Above that the DME no longer uses data from the AFM.

[Purplehazedog]

The AFM was a used one but I had the same problems. So I swapped my old one back in. I've been very busy at work so I plan on working on the car over the next few days.

[603Racing]

Do you have an air/fuel ratio gauge in that race car? Fuel pressure gauge? This data would be helpful.

[Purplehazedog]

Well guys, swapped out the TPS from another car and same issues. I also replaced the crank sensor to no avail. I swapped out the three relays that are on the drivers side next to the strut tower, and nothing.

Could I have a bad Distributor module?

[FLG]

Did you check the air gap on the cps?

Also might be wise to hook up a fuel pressure gauge and see whats happening at the cutout point.

[Purplehazedog]

I did not check the gap on the CPS. .040 right? could that cause this problem?

[FLG]

Yes and yes, too far and you could be fine at lower rpm but start to loose data at high rpm.

Sent from my Galaxy Nexus using Tapatalk 2

[saturnv7890]

Might be worth a shot, I had an issue similar and it was the C191. A bad connection causes poor injector performance.

Took me 20 minutes with a soldering iron and all these issues I had been chasing for months disappeared. Might be worth checking out!


If you do it, I'd recommend a 7 pin weather proof connector and some serious dielectric grease, I just soldered all the wires together and bypassed the connector

[Purplehazedog]

I opened up the C191 connector. It looked perfect?!? (the inside connectors and the wires on the bottom). I added dielectric grease and I still have the problem. Not sure if it is something else, or If I should just replace and solder the wires together just because. I have not idea what to do next.

[ak-]

Swap ECU's with a friend.

edit: whoops. Looks like you tried that.

Check the harmonic balancer to see if it wobbles giving the CPS a bad signal.