Stumblin in
Thread Starter
Registered User
Joined: Mar 1999
Posts: 245
From: Berkeley Spgs, WVA
Stumblin in
Yes, another stumble issue.
Started last week whe the car was hard to start and the battery had just ran out of gas. I put a new battery in and rewired my Mez waterpump relay ground through a switch and added an indicator lamp to see when the pump is running. I did all this because I noticed the 30 amp relay was drawing some power all the time from the battery. Seemed a constant drain, plus the battery was a few years old.
For the HARD TO START, I pulled the plugs and replaced them with Delco 906's. All the old plugs had the gaps opened to at least .065.
With that done the car started fine but had a definitite stumble most noticeable under load and in 4th gear or above.
Further checking revealed the coil wire at the terminal was badly decomposed. Checking the opti waires, some of them were near disintegration, so I replaced the opti with a NEW GM unit (thank you Jason Cromer) and went with Thunder racing OVC Taylor wires. I cleaned the TB, EGR valve,TPS switch as part of the mini project.
Well my stumble is still there so today I went to NAPA for some FI cleaner and a new fuel filter and after the run into town I decided to park it on the lift and have a look under the car. I see my CAT is glowing red, in the middle, so my assumtion is that its clogged or shot. It is an original unit and the exhaust end is rusted through where it connects to the s-pipe and I have a 94009 Magnaflow and O2's already on order. My O2's are original also.
DMaster run shows high knock counts, but only big increases while driving. I am guessing the s-pipe is bouncing around enough so the knock sensor may be picking this up.
Any thoughts on my on this? Can a cat cause stumble? Also, anyone have a source for an S-Pipe?
Started last week whe the car was hard to start and the battery had just ran out of gas. I put a new battery in and rewired my Mez waterpump relay ground through a switch and added an indicator lamp to see when the pump is running. I did all this because I noticed the 30 amp relay was drawing some power all the time from the battery. Seemed a constant drain, plus the battery was a few years old.
For the HARD TO START, I pulled the plugs and replaced them with Delco 906's. All the old plugs had the gaps opened to at least .065.
With that done the car started fine but had a definitite stumble most noticeable under load and in 4th gear or above.
Further checking revealed the coil wire at the terminal was badly decomposed. Checking the opti waires, some of them were near disintegration, so I replaced the opti with a NEW GM unit (thank you Jason Cromer) and went with Thunder racing OVC Taylor wires. I cleaned the TB, EGR valve,TPS switch as part of the mini project.
Well my stumble is still there so today I went to NAPA for some FI cleaner and a new fuel filter and after the run into town I decided to park it on the lift and have a look under the car. I see my CAT is glowing red, in the middle, so my assumtion is that its clogged or shot. It is an original unit and the exhaust end is rusted through where it connects to the s-pipe and I have a 94009 Magnaflow and O2's already on order. My O2's are original also.
DMaster run shows high knock counts, but only big increases while driving. I am guessing the s-pipe is bouncing around enough so the knock sensor may be picking this up.
Any thoughts on my on this? Can a cat cause stumble? Also, anyone have a source for an S-Pipe?
Thread Starter
Registered User
Joined: Mar 1999
Posts: 245
From: Berkeley Spgs, WVA
Re: Stumblin in
Surpised nobody responded to another stumble problem. No matter as it is fixed. So for further people searching for stumbling type issues I'll elaborate what I found. Symtoms described already.
I did find both O2's were defective. OHM meter showed the right side reading 4.3 ohms, while the left was OPEN. I also re-pulled the AC delco plugs and replaced them with NGK TR55's. ALL plugs on the drivers side (1,3,5,7) were coated in black soot. Plugs on the passenger side had a bit of soot but overall were fairly clean.
Plug 4 was the culprit. Its electrode was bent into the electrode. I must have dropped it at some point and not recheck the gap again. Boy do I feel stupid for that boner.
I had hopes of taking my car to the American Muscle Car Federation show last saturday, but my Z has been the lift queen .
Oh well... I took my MACH1 and got a second place in the modified class so it wasnt a total loss.
Hope this helps someone down the road.
I did find both O2's were defective. OHM meter showed the right side reading 4.3 ohms, while the left was OPEN. I also re-pulled the AC delco plugs and replaced them with NGK TR55's. ALL plugs on the drivers side (1,3,5,7) were coated in black soot. Plugs on the passenger side had a bit of soot but overall were fairly clean.
Plug 4 was the culprit. Its electrode was bent into the electrode. I must have dropped it at some point and not recheck the gap again. Boy do I feel stupid for that boner.
I had hopes of taking my car to the American Muscle Car Federation show last saturday, but my Z has been the lift queen .
Oh well... I took my MACH1 and got a second place in the modified class so it wasnt a total loss.
Hope this helps someone down the road.
Last edited by QUASARBLUEZ28; Aug 3, 2006 at 04:50 PM.
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