'89 Cavalier 2.8L Z24 won't accelerate over 25mph, car just jerks.

[1990Cavz24]

Yeah I figured it was a long shot. I still think it sounds CPU although my initial feeling was fuel pressure until I read the post where the fuel pressure tested fine (including dead heading the pump by shutting the vaccuum off to the regulator). Only thing I note is that the readings were not given. If someone was going on the TBI #'s (15-20psi) instead of the MPFI #'s (35-40 regular running and upwards of 60 under full pressure) that may be where the error lies. Wonder what the readings obtained were.

[pappyl]

Will need to hook it up to a scanner and monitor what's going on.
I would suspect the TPS (throttle position sensor).

What could be causing this...
1) insufficient fuel pressure (pump not keeping up, bad regulator)
2) timing not advancing properly (bad ignition control module)
3) Computer thinks everything ok
- bad prom
- bad sensors (like TPS) flatline and lie to computer
- maybe a physical interference on throttle

If timing chain skipped a tooth it should be idling like a dog.

[matthew24u]

the compression could all be 50 psi it would still rev up and accelerate you don`t have a compression problem. I would get a scantool & look at injector pulse with sounds like your not getting fuel delivery to the engine. should be TBI if so you can look in the TB and rev it up under the hood and see your fuel spray just dumping everywhere at WOT. IF you can`t then you have got injector or PCM problem. signed, always stuck in diagnostics!

[Joe W]

This does seem to be a possible VSS issue, although I must question why a code has not been set, the same reguarding the CPU, even through failure they throw a code. Have you tested the VSS?