Another stumble problem
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 3,252
Likes: 6
From: The Colony Tx
Another stumble problem
Need help. I have the typical off idle stumble, 88 base. Things I have tried (Car needed had over 40k miles since last tune up so I don't feel tune items a waste of money)
New: Plugs, wires, cap, rotor, coil, O2 sensor. Checked TPS and it is right on factory setting. The plugs looked like I had just put them in so there is no indication of not firing.
I even went to a Corvette garage and had the TPS checked just in case I suddenly got stupid. Checked OK there. Talking to the owner he said that the stumble is one of the toughest problems to trouble shoot. He had just had an 86 that the owner felt he had spent enough with no results and finally took the car home.
Any suggestions will be appreciated. I am 68 and the eventual plan is to leave it to my daughter at check out time. Would really like to have it running well at that time.
Thanks. Jon
New: Plugs, wires, cap, rotor, coil, O2 sensor. Checked TPS and it is right on factory setting. The plugs looked like I had just put them in so there is no indication of not firing.
I even went to a Corvette garage and had the TPS checked just in case I suddenly got stupid. Checked OK there. Talking to the owner he said that the stumble is one of the toughest problems to trouble shoot. He had just had an 86 that the owner felt he had spent enough with no results and finally took the car home.
Any suggestions will be appreciated. I am 68 and the eventual plan is to leave it to my daughter at check out time. Would really like to have it running well at that time.
Thanks. Jon
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 3,252
Likes: 6
From: The Colony Tx
Went out to check timing and now I am completely confused. Unpluged the brown/black wire. Hooked up timing light. No grove where I expected. Got some red and white paint and did about 2" of the balancer in red and the white on the timing mark.
Waited for paint to dry and tried again. No red paint around the timing mark.
Is it possible to install the balancer 180 out? I know on the older engines if you left the key-way out and just used the bolt you could tighten enough to drive the car.
Waited for paint to dry and tried again. No red paint around the timing mark.
Is it possible to install the balancer 180 out? I know on the older engines if you left the key-way out and just used the bolt you could tighten enough to drive the car.
Intermediate
Joined: May 2011
Posts: 44
Likes: 0
From: Michigan
I have the same problem with my '94 LT1. It runs strong and smooth above idle, doesn't seem to misfire. But it stumbles for a second when stomping the gas right off idle. I made the mistake of cleaning the interior of the throttle body harshly and wonder if I removed the coating and perhaps that is causing the problem.
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 3,252
Likes: 6
From: The Colony Tx
I have the same problem with my '94 LT1. It runs strong and smooth above idle, doesn't seem to misfire. But it stumbles for a second when stomping the gas right off idle. I made the mistake of cleaning the interior of the throttle body harshly and wonder if I removed the coating and perhaps that is causing the problem.
Safety Car
Joined: Jan 2006
Posts: 3,940
Likes: 42
From: shavertown Pa.
If you can't find the timing mark, you either are not connected to No1 wire, or someone moved the dist.
The timing might be way too high, my bet is a small vac leak, my car had leaks, one big one was the egr gasket, the next and worst was the O rings around the injectors.
I had just installed new injectors, but the O rings that came with the new injectors were barely touching the walls, I took it apart again and installed new heavy silicone O rings.
Then I found one of the lines running to the cruise was burnt on the bottom, hanging near the exhaust manifold.
Long story shortened, my car runs and idles great at 8 degrees timing, I get a spark knock on 89 octane, so I switched to 91 the car runs great and gets 24Mpg in town.
Those vac leaks can make you crazy I know I spent many hours over a hot L98 tracing all mine.
The timing might be way too high, my bet is a small vac leak, my car had leaks, one big one was the egr gasket, the next and worst was the O rings around the injectors.
I had just installed new injectors, but the O rings that came with the new injectors were barely touching the walls, I took it apart again and installed new heavy silicone O rings.
Then I found one of the lines running to the cruise was burnt on the bottom, hanging near the exhaust manifold.
Long story shortened, my car runs and idles great at 8 degrees timing, I get a spark knock on 89 octane, so I switched to 91 the car runs great and gets 24Mpg in town.
Those vac leaks can make you crazy I know I spent many hours over a hot L98 tracing all mine.
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Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 3,252
Likes: 6
From: The Colony Tx
Looks like the dist is 180 out. Looking at the manual it shows the number 1 wire should be on the engine side of the dist. Mine is on the firewall side. I guess I will try pulling the dist and put it back the way the manual says.
Thanks for the recommendation.
Thanks for the recommendation.
Intermediate
Joined: May 2011
Posts: 44
Likes: 0
From: Michigan
If you do, make sure you only use a solvent made specifically for throttle bodies, and I would NOT recommend scrubbing at all, even if there is tough build up. I have been looking for a way to reapply the coating, or have it done, but haven't found anyone talking about it on any forum.
Intermediate
Joined: May 2011
Posts: 44
Likes: 0
From: Michigan
If you can't find the timing mark, you either are not connected to No1 wire, or someone moved the dist.
The timing might be way too high, my bet is a small vac leak, my car had leaks, one big one was the egr gasket, the next and worst was the O rings around the injectors.
I had just installed new injectors, but the O rings that came with the new injectors were barely touching the walls, I took it apart again and installed new heavy silicone O rings.
Then I found one of the lines running to the cruise was burnt on the bottom, hanging near the exhaust manifold.
Long story shortened, my car runs and idles great at 8 degrees timing, I get a spark knock on 89 octane, so I switched to 91 the car runs great and gets 24Mpg in town.
Those vac leaks can make you crazy I know I spent many hours over a hot L98 tracing all mine.
The timing might be way too high, my bet is a small vac leak, my car had leaks, one big one was the egr gasket, the next and worst was the O rings around the injectors.
I had just installed new injectors, but the O rings that came with the new injectors were barely touching the walls, I took it apart again and installed new heavy silicone O rings.
Then I found one of the lines running to the cruise was burnt on the bottom, hanging near the exhaust manifold.
Long story shortened, my car runs and idles great at 8 degrees timing, I get a spark knock on 89 octane, so I switched to 91 the car runs great and gets 24Mpg in town.
Those vac leaks can make you crazy I know I spent many hours over a hot L98 tracing all mine.
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 3,252
Likes: 6
From: The Colony Tx
This may sound a little strange, but I use about a 3 ft length of garden hose. You would be suprised how it amplifies the sound an air leak has. I bought an automotive stethoscope and it sucked compared to the hose trick.
Another positive is if you attended the School of Graceful and stick it in the fan blades it won't take your head/hands off. Don't ask how I know
Another positive is if you attended the School of Graceful and stick it in the fan blades it won't take your head/hands off. Don't ask how I know
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The ring on your harmonic balancer might have slipped out of place (mine did that).