Strange miss
Thread Starter
Instructor
Joined: Mar 2007
Posts: 169
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From: Tullahoma Tennessee
Strange miss
I had the vette out yesterday (thank God it's finally driveable) and it ran fine. Got to autozone and on the drive back i noticed a miss, keep in mind that I'm diagnosing with very limited car experience since I am sixteen. I'd describe it as a sputtering, the car still runs strong it just sounds terrible. Ok so then I took it out today and basically the same thing, I drove it to work and it acted fine, then on the way home the sputtering was back. The noise isn't noticeable at all at idle but when the rpms hit about 2000 it makes the putting noise. So right now I think I'm running on 7 cylinders. I'll pull spark plugs tomorrow, I also noticed that one of the spark plug wires was up against the exhaust manifold, 
I thought this might be contributing to the problem. I would appreciate any replies. 
I thought this might be contributing to the problem. I would appreciate any replies.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
The best thing you can do is a full tuneup. The carb probably needs to be tuned / rebuilt. PM Lars here on the forum about having his magic done to it.
Then, I would replace all the plugs and wires, cap, rotor, and then time the engine proper.
If you haven't done so already, an oil change, filter changes, and shine a light down in the tank to see if everything is cool where the gas is sucked up. If there is a lot of crap in the tank the sock may be clogged and the bladder int he tank may have fallen and is wrapping up the pickup.
Then, I would replace all the plugs and wires, cap, rotor, and then time the engine proper.
If you haven't done so already, an oil change, filter changes, and shine a light down in the tank to see if everything is cool where the gas is sucked up. If there is a lot of crap in the tank the sock may be clogged and the bladder int he tank may have fallen and is wrapping up the pickup.
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
first, check out that exhaust/wire issue you found. Many "cheaper" wire sets will burn thru and let electrical impluse to spark plug short out to ehauxt manifold. That will cause a miss, sometimes intermittent. DB is correct in implying that plug wires must be in good shape, along with the rest of the ignition system. Try and keep plug wires from resting on any metal surface,keep them seperated as best you can to prevent "cross firing".
Thread Starter
Instructor
Joined: Mar 2007
Posts: 169
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From: Tullahoma Tennessee
Thanks guys, I'm probably going to invest in a pair of wire looms, also I neglected to mention the carb is a Holley 750 VS meaning my engine is over carbed at the moment. The carb has not been tuned at all 
I am once again going to sound stupid, but I've heard people on here mention setting the float bowls. Could that be another issue? 
I am once again going to sound stupid, but I've heard people on here mention setting the float bowls. Could that be another issue?
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Thanks guys, I'm probably going to invest in a pair of wire looms, also I neglected to mention the carb is a Holley 750 VS meaning my engine is over carbed at the moment. The carb has not been tuned at all I am once again going to sound stupid, but I've heard people on here mention setting the float bowls. Could that be another issue?
I am once again going to sound stupid, but I've heard people on here mention setting the float bowls. Could that be another issue? When you pull your plugs lay them all out in rows, one for driver's side and one for passenger side and take close up pics of each set's tip.
The colors will tell some of the story as far as rich or lean.
That carb is a bit too much for that engine but it can be tuned down some. Have you looked for a smaller carb? They can be bough on Ebay. Try to find a year specific Q-jet that needs to be rebuilt. Maybe $30 or so. Then have it rebuilt by Lars and you'll be good.
Thread Starter
Instructor
Joined: Mar 2007
Posts: 169
Likes: 0
From: Tullahoma Tennessee
No that carb will be great for the setup I'm going to have eventually. I'm just working on a budget and can't afford it yet. The setup I'm looking at right now is: Edelbrock RPM air gap intake, Edelbrock E-tec heads and a fairly mild cam. Hoping to get in the neighborhood of 400 HP.
Team Owner
Joined: Jul 2004
Posts: 40,408
Likes: 792
From: Redondo Beach, California
Engine stumbling and misfiring can also be symptoms of something wrong with the exhaust gas recirculation (EGR) polution control system.
Looks like you have an earlier model C3 which I suppose does have an EGR. I think on C3's you can avoid EGR problems by just disconnecting it and retuning the engine to run without it.
Looks like you have an earlier model C3 which I suppose does have an EGR. I think on C3's you can avoid EGR problems by just disconnecting it and retuning the engine to run without it.
