slovie

My 1991 zr1 runs great in valet mode but in full power starts to bog most of the time when engine warms up?? any ideas

FASTAZU

Two things come to mind secondary fuel pump or vacuum issues. You really need to hook up a scanner to see whats not working.

Goldcylon

and one other thing secondary injectors since the OP did not mention a SES alight in the DIC. GC

ccmano

with all of the above. Just had that with mine, it was like the secondaries didn't work a all. Turned out to be a collapsing intake accordion. The one between the air filter housing and the throttle body.
I simply took the accordion off a drove it without it, what a difference.
I fabricated two Haibeck style hoops, put them in the accordion and reassembled. All good. Some times it's the simple things, sometimes it's not.
H

1971 Judge

Yep - I just purchased the "accordion loops" from Haibek for this reason as well.

slovie

just eliminated accordion no change noticed that the power was good when the engine was cold worse when heated not that good even in valet. still hunting look for someone that can troubleshoot in my area I guess

darklordftt

Are the injectors stock? Mine is the same way, except there is a cluncking sound coming from under the car when in neutral, due to the engine misfiring from the injectors being bad. It gets worse as the engine warms up. No dash lights either.

Paul Workman

I'd want to start with what the fuel pressure reads, ESPECIALLY at WOT. (Should read 52 ro 55 psi @ WOT, dropping back to atound 45ish cruising.)

slovie

zr1 stock 4000 mi. any experts in the Detroit area ? other than Les Stanford ?

ShawnZR-1

How does it idle when it's warmed up? Does it bog under normal acceleration or once it passes a certain RPM?

I had an issue with injectors and fouled plugs (one begets the other). 4000 miles is pretty low, injectors rust and stick... I'd do a fuel system pressure bleed test and check all of the plugs.

Z51JEFF

The injectors died in my 91 @8000 miles so you can't rule out low miles.

ShawnZR-1

Agreed, they're more likely going to quit from non use than from being exercised often

slovie

Probably could rule that out before operating temp runs very strong in power mode maybe a fuel problem pressure when hot though sure is troubling when no trouble light indication occurs. Thanks for input

bad-zr1

Both fuel pumps run until about 176 degrees and then the secondary turns off until called for (WOT full power). See if starts running bad about 175 or so. Could be a week primary pump.
You can pull the fuses on each pump to check pressure from each.

mhobtr

please delete this post