Mystery Missfire Solved! - ZR-1 Net Registry Forums

tccrab · 09-22-2006

For those that have been following my posts for the last month or so, Success at last!
Girlfriend purrs like a kitten! YAY!

At little History:
'90 ZR1, 10,900 miles.
After a hot restart, small misfire was noticed, that got worse and worse on the 25 mile ride home.
When I pulled her into the garage, it sounded like I was getting ready to drop a rod. Now I know what the dual mass flywheel sounds like when it's trying to shake itself apart.

Subsequent investigation discovered that one primary fuel injector failed, two more out of spec.
Replaced both primary and secondaries with Accel 150121 using Haibeck's special "O" rings for the primaries.
Started her up, still a misfire on 4, 6, 7.

Removed plenum, found secondary fuel injector "O" ring not seated properly on cylinder 6, replaced the damaged "O" ring.
Now only missing on 4 & 7.

Interstingly enough, this would indicate a coil problem as those two cylinders are on the same coil.
Trouble is, got spark. Coils Ohm correctly.
Plenum comes off again (10 minutes Johnny? Are you kidding?), check all fuel injectors again, and their connectors. Check the coils and their connections.
Everything OK, so button her back up and restart her.
Still a misfire on 4 & 7.

Borrowed a ECM from a fellow Forum member (A MILLION THANKS, you know who you are, enjoy the Bubbly, it's the best from the Napa Valley), and problem goes away.
YAY!
Searched online, ECM's are availabe from quite a few different places, but they all need you to send your ECM to them and they have it repaired, gosh knows how long that would take.
At Haibecks' advice I call the local Chevvy shop and they have one for me in one day for $134 plus $15 for overnight shipping.

Welcome home Girfriend.

I'm glad that your're back.

And the wife's glad that I won't be spending so much time under her hood and spending so much money. Why are women so jealous of cars?

Fuel Injectors:
$525 (Atlantic Racing/Summit Racing)
Top End Gasket Kit
$180 (Thanks JeffVette)
ECM
$150 (Local Chevvy Shop)
PCV connector and assorted vacuum hoses and connectors:
$75 (White Racing, thanks Limey and also JeffVette)
Haibeck's "O" rings (what a great guy, VERY HELPFUL, I sould probably send him a bottle of Bubbly too... hmmm...)
$20
Oil & Filter & antifreeze
$75

Roughly, $1k.
Now she's good as new, and actually idles much better that she ever did.
What a relief!

TomC
'90ZR1 #792

tomtom72 · 09-22-2006

Hey Tom,

Tom

09-22-2006	#1
tccrab Join Date: Oct 2004 Location: Folsom CA Posts: 1,655	Mystery Missfire Solved! For those that have been following my posts for the last month or so, Success at last! Girlfriend purrs like a kitten! YAY! At little History: '90 ZR1, 10,900 miles. After a hot restart, small misfire was noticed, that got worse and worse on the 25 mile ride home. When I pulled her into the garage, it sounded like I was getting ready to drop a rod. Now I know what the dual mass flywheel sounds like when it's trying to shake itself apart. Subsequent investigation discovered that one primary fuel injector failed, two more out of spec. Replaced both primary and secondaries with Accel 150121 using Haibeck's special "O" rings for the primaries. Started her up, still a misfire on 4, 6, 7. Removed plenum, found secondary fuel injector "O" ring not seated properly on cylinder 6, replaced the damaged "O" ring. Now only missing on 4 & 7. Interstingly enough, this would indicate a coil problem as those two cylinders are on the same coil. Trouble is, got spark. Coils Ohm correctly. Plenum comes off again (10 minutes Johnny? Are you kidding?), check all fuel injectors again, and their connectors. Check the coils and their connections. Everything OK, so button her back up and restart her. Still a misfire on 4 & 7. Borrowed a ECM from a fellow Forum member (A MILLION THANKS, you know who you are, enjoy the Bubbly, it's the best from the Napa Valley), and problem goes away. YAY! Searched online, ECM's are availabe from quite a few different places, but they all need you to send your ECM to them and they have it repaired, gosh knows how long that would take. At Haibecks' advice I call the local Chevvy shop and they have one for me in one day for $134 plus $15 for overnight shipping. Welcome home Girfriend. I'm glad that your're back. And the wife's glad that I won't be spending so much time under her hood and spending so much money. Why are women so jealous of cars? Fuel Injectors: $525 (Atlantic Racing/Summit Racing) Top End Gasket Kit $180 (Thanks JeffVette) ECM $150 (Local Chevvy Shop) PCV connector and assorted vacuum hoses and connectors: $75 (White Racing, thanks Limey and also JeffVette) Haibeck's "O" rings (what a great guy, VERY HELPFUL, I sould probably send him a bottle of Bubbly too... hmmm...) $20 Oil & Filter & antifreeze $75 Roughly, $1k. Now she's good as new, and actually idles much better that she ever did. What a relief! TomC '90ZR1 #792 __________________ TomC '90ZR1 #792 Honorary Pirate [B]If it ain't FUN, you're doing something terribly WRONG. [/B]

09-22-2006	#2
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,645	Re: Mystery Missfire Solved! Hey Tom, Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member