1990 ZR-1 Misfire Carbon'd up 2 & 7, BLM 115 at idle

[J & J Speed Shop]

Looking for some help or something that I missed. I am working on a 1990 Corvette ZR-1. The vehicle originally came in and the dual mass flywheel was banging like crazy at idle. I ordered the brand new injectors from FIC and replaced both the primaries and secondaries. The idle misfire was greatly improved and 4-5 injectors were bad 3-4 ohms and about 3-4 were questionable under 10 ohms. The vehicle has new spark plugs, coil and oxygen sensors. There is still a slight miss at idle BLMs rich at 115 and INT around 89-94. If I drive the car down the street it is fine at part throttle, but once you try to go WOT in normal power mode the car falls on its face misfires like crazy and will not clean up. Turn the switch to full power mode and it will stumble for a split second and then accelerate normally. I have already checked fuel pressure, and I have spark with a tester on all cylinders including 2 & 7. Did a compression 215 psi and leakdown and everything checks out. If I pull the plugs they all look normal except 2 & 7. Both of these plugs have a good amount of carbon buildup. I also saved the old plugs I removed before I started this job and noticed 1 plug from each bank was more carbon'd then the rest of the plugs. I don't know weather it was 2 & 7 but I assume it was. At first I was thinking maybe I received 2 bad primary injectors but the plugs before the injectors kind of ruled that out in my mind.

I was thinking maybe a bad ECM ?? Suggestions please help

[Schrade]

Welcome onto the boards there...

[J & J Speed Shop]

Welcome onto the boards there...

Thank you. If this car wasn't driving me crazy I would be doing a lot better

[FU]

2 & 7 share the same coil.
Wire's on right ?
Bad wire's on 2 & or 7
Coil bad

[J & J Speed Shop]

2 & 7 share the same coil.
Wire's on right ?
Bad wire's on 2 & or 7
Coil bad

2 & 7 do not share the same coil. Coils are 8/5 1/6 4/7 3/2

Yes I have the wires firmly on the coils as well as the spark plug end. The coils are all brand new and I checked the one wires and had approx 17,000 ohms of resistance on the number 2 which is a long wire

[FU]

Oops 4 & 7 - 3 & 2

Check 4 pin connector at the coil pack maybe not connected right.
Arching wire.
Mile's on car ?

[J & J Speed Shop]

Oops 4 & 7 - 3 & 2

Check 4 pin connector at the coil pack maybe not connected right.
Arching wire.
Mile's on car ?

Checked all the coil pack connectors and the car has approx 20,000 miles

[WARP TEN]

Did you eventually figure out what the problem was? It sounded from your initial post that you were quite thorough in your work, but there are a few idiosyncrosies to these engines. If not, and if you have not done so already, you might contact Marc Haibeck (website www.zr1specialist.com (http://www.zr1specialist.com)). He should be able to shed some light on it. Good Luck--Bob

[jimmy b.]

Double check all the vacuum lines especially the map sensor , this could cause some of the symptoms you described. Hope this helps..jimmy

[FU]

:happy1: curious to know what the problem was-is.