1990 MY Hesitation/ stumble of engine - ZR-1 Net Registry Forums

jrd1990zr1 · 05-16-2021

Was having this problem late last year, When at idle cold there seems to be a miss, like a bad wire. When the engine warms up the situation is not quite as bad but if you step on it the engine hesitates then seems to catch.

Over the winter I pulled the plenum, new set of GM wires, checked the coils. This Spring, same problem. Changed the injectors (FIC) about 9 years ago so they were supposed to be ethanol compliant and at the same time changed the plugs. This was about 30,000 miles ago. Car has 62,000 on it I don't drive it a lot each year.

I am at a loss, seems like next step is another set of plugs?

Can a set of FIC injectors go bad at about 30,000 miles?

Any suggestions on how to diagnose this issue? Is there a simple procedure to check the injectors without pulling the plenum?

Any suggestions would be appreciated. Thanks.

05-16-2021	#1
jrd1990zr1 Join Date: Dec 2005 Location: Delanson, NY Posts: 925	1990 MY Hesitation/ stumble of engine Was having this problem late last year, When at idle cold there seems to be a miss, like a bad wire. When the engine warms up the situation is not quite as bad but if you step on it the engine hesitates then seems to catch. Over the winter I pulled the plenum, new set of GM wires, checked the coils. This Spring, same problem. Changed the injectors (FIC) about 9 years ago so they were supposed to be ethanol compliant and at the same time changed the plugs. This was about 30,000 miles ago. Car has 62,000 on it I don't drive it a lot each year. I am at a loss, seems like next step is another set of plugs? Can a set of FIC injectors go bad at about 30,000 miles? Any suggestions on how to diagnose this issue? Is there a simple procedure to check the injectors without pulling the plenum? Any suggestions would be appreciated. Thanks. __________________ 1968 convertible Lemans Blue, 1986 coupe Medium Blue NCRS Top Flight (sold), 1990 ZR1 #2529 Red NCRS Regional and National Top Flight (sold), 1990 ZR1 #2124 Charcoal Metallic NCRS Top Flight 2010 & 2018, 2003 Anniversary Red Convertible (sold)