'90 N/A engine, stumbles above 6K intermittantly...WHY?!!!
 

I would just like opinions from the masses as to why a NA engine would stumble above 6000 RPM sometimes so bad that it wont go above 7K at wide open throttle.

Other times its fine.

Secondary injectors are new and not at fault.

Opinions please...

Adequate spark?

TPS. I bet a dollar.

When my TPS went out on my old '91 it only stumbled on idle though. But I guess it could be. I am not the best at troubleshooting.

When my TPS started going bad on my TII, it did exactly what he described...especially after washing the engine.

When it died completely, the car wouldn't rev over 1500.

I assumed as much.
I gave the owner of the car a new TPS to install.

He had to leave.

I was doing this as warranty work on the 1990 GXL I just sold him.

I'll see if that does the trick.
(It has a lumpy/low idle sometimes too, but not all the time.)

Hey, before you spend money on a new TPS, try regrounding the ecu and block. I'm trying to help someone else with a problem that sounds similar to yours. I've found some possible causes but the regrounding sounds like the best place to start. It's good to hear that your injectors are new, narrows it down. Good luck.

-Colby

the grounding isnt a problem either.
I scoped the voltage drops and got no noticable difference anywhere.

Im calling the new owner to see if the TPS is the trick.

Make sure the new TPS is adjusted properly.l..otherwise it'll still seem like the problem.

cats ?
 

heh...i remember those days...mine used to do that...
rev good until about 6 or 7k...and take forever to redline..it was those good ole stock cats...i switched it out with a bonez highflo cat....boy! it made miracles happen...it brought her back alive

Mine had that problem....
I re-grounded everything, did the timing, TPS, and reset the ECU.
It went away.
I can duplicate the EXACT same problem by over-richening my S-AFC.
The ECU was over-riching for some reason... and my mileage was around 12 mpg.
It's all fine now!
Yours could be that, or something else.