Misfire cylinder #5
Thread Starter
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Joined: May 2014
Posts: 91
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Misfire cylinder #5
Hey guys!
Got a 99 C5 A4 Corvette..
Mods :
Fast 78 Intake
Long tube headers
Catback
Vararam
Plugs + wires are brand new.
So the car misfires a lot on idle and when going easy on the pedal...Seems to be normal at wot.
Went to my friends place and hooked it up to his scanner to see real time misfires... A lot on #5
We changed plug, wire, changed the coil pack with another one, I even reinstalled my stock intake and the misfire is still there... Sometimes the car will run and idle just fine and sometimes I start it and it would run like complete crap. I installed brand new injectors o-rings everywhere, cleaned the surface between head/manifold and still that intermitent misfire...
Any suggestions???
Got a 99 C5 A4 Corvette..
Mods :
Fast 78 Intake
Long tube headers
Catback
Vararam
Plugs + wires are brand new.
So the car misfires a lot on idle and when going easy on the pedal...Seems to be normal at wot.
Went to my friends place and hooked it up to his scanner to see real time misfires... A lot on #5
We changed plug, wire, changed the coil pack with another one, I even reinstalled my stock intake and the misfire is still there... Sometimes the car will run and idle just fine and sometimes I start it and it would run like complete crap. I installed brand new injectors o-rings everywhere, cleaned the surface between head/manifold and still that intermitent misfire...
Any suggestions???
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Just for grins,,, try a couple of things:
Examine the schematics below and measure the test slots on top of all the fuses to chassis ground. Some will need the ignition ON to be hot.
You should see full battery voltage on each fuse.
You should disconnect the connectors for the coils and read the ground wire to a known good ground to make sure that you dont have a poor ground.
Examine the schematics below and measure the test slots on top of all the fuses to chassis ground. Some will need the ignition ON to be hot.
You should see full battery voltage on each fuse.
You should disconnect the connectors for the coils and read the ground wire to a known good ground to make sure that you dont have a poor ground.
Thread Starter
Advanced
Joined: May 2014
Posts: 91
Likes: 0
Oh well..Updates :
We changed plugs, wires, changed the coil pack with another one, I even reinstalled my stock intake and the misfire is still there... Sometimes the car will run and idle just fine and sometimes I start it and it would run like complete crap. I installed brand new injectors o-rings everywhere, cleaned the surface between head/manifold and still that intermitent misfire...
I also checked for vacuum leaks with brake cleaner, could not find anything. Changed the manifold gaskets...Tried running the car without the evap valve ( maybe it would be stuck open/closed ) still the same...
So I get a P0300 code and checked about everything I could...I'll check AGAIN the ground behind the driver side head tomorrow morning. Ill also try to clean the MAF sensor.
I ran the car a bit more and noticed this...Sometimes will run fine, but let's say I start it up and it misfires and runs like crap and go for a ride it keeps missing and backfiring, but if I get on it and go WOT for a couple sec everything goes back to normal after...
Ideas?
We changed plugs, wires, changed the coil pack with another one, I even reinstalled my stock intake and the misfire is still there... Sometimes the car will run and idle just fine and sometimes I start it and it would run like complete crap. I installed brand new injectors o-rings everywhere, cleaned the surface between head/manifold and still that intermitent misfire...
I also checked for vacuum leaks with brake cleaner, could not find anything. Changed the manifold gaskets...Tried running the car without the evap valve ( maybe it would be stuck open/closed ) still the same...
So I get a P0300 code and checked about everything I could...I'll check AGAIN the ground behind the driver side head tomorrow morning. Ill also try to clean the MAF sensor.
I ran the car a bit more and noticed this...Sometimes will run fine, but let's say I start it up and it misfires and runs like crap and go for a ride it keeps missing and backfiring, but if I get on it and go WOT for a couple sec everything goes back to normal after...
Ideas?
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
When its running like crap,,,,,,,,,,,,,,,,,,,,, Read the voltage on the fuel pump fuse, & coil fuses 16 & 22. You should see full battery voltage at eash fuse IGNITION Switch ON
There are test points on top of each fuse.
Bill
There are test points on top of each fuse.
Bill
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Drifting
Joined: Sep 2009
Posts: 1,719
Likes: 4
From: cinnaminson n.j.
St. Jude Donor '14
you can get a noid light and plug it into #5 injector connector when it is misfiring. It should blink consistantly. Swap it to a good cylinder to see what it should look like. This will show you if there is a problem on #5 injector circuit. If it's good, clear the code and swap the injector with #3 and see if the miss follows. 