91 zeee

heres the deal....91 z28. 305 tpi. stock except i did replace all the injectors (ford svo injectors) about 15000 miles ago.

from a stop..wide open throttle... pulls good then gets to about 4500 rpm and just flat stops accelerating. rpms 'hang' at 4500, car doesn't shift...it does this for about 2 seconds and then will shift and start pulling again.

new plugs, wires, cap, rotor, , etc... i thought i had a clogged cat converter (was original one) so i replaced it, same thing, no change.

i checked fuel pressure thinking maybe i had a pump or regulator...pressure looked good.

sometimes it does not exhibit this problem at all...winds up to about 5000, shifts and keeps pulling. but most of the time it gets to 4500 or so and just stops.....any thoughts? (i did adjust the TV cable as well thinking it was a trans issue at first)

bjankuski

Does it rev up to 5000 RPM when the engine is cold or warm? One thought would be bad hyd lifters or weak valve springs cuusing the engine to float the valves at 4500 RPM. Are you sure you are not getting some intake restriction?

Orr89RocZ

iTrader: (20)

Anything ignition related? Trans usually wont hang rpms. Valvefloat may or may not. I have had both happen with valvefloat or worn intake guides, sometimes car will pull thru valvefloat but be down on power, sometimes it hangs up at rpm.

Ignition falling out or not hot enough spark could act like a limiter.

Could pop valve covers off and check springs. Make sure pushrods are straight and oil is getting to top of valvetrain

91 zeee

Yes. In neutral it revs fine. What sort of intake restriction could I have?

91 zeee

If it was valvefloat wouldn't I be getting alot of blowby coming out of the exhaust? Because I dont see anything.

It feels like it could be an ignition issues, however, it is not breaking up or missing at all.

How do I check the valve springs? I dont have the $200 tool... is there a another way?

Guest

Could be the trans/converter...

ask me why I said that...I lost 10 mph in 3rd...then the 3-4 band a bit later....

Azrael91966669

i had the same issue with ford injectors they are ment to run at higher psi to give the posted lbs per hour if running 19 svos in a gm they run closer to 16 17 lb do this for a test pull the vac line off the fpr and ill bet overall your power feels better then will still feel flat at high rpm its because the pressure boost puts the injectors closer to where they should be when in a ford and as rpm climbs you need even more pressure
as soon as i went back to a set of multitecs the problem dissappered completly

Street Lethal

iTrader: (16)

It's called an ECM restriction, it pulls timing based on information being received during Closed Loop, as I assume it happens when the engine is warm, and not when its cold...?