Bought a used C3...
Thread Starter
2nd Gear
Joined: May 2016
Posts: 2
Likes: 0
Bought a used C3...
This last weekend I bought a used 1979 and the seller said it just won't run well. At 3000$ I couldn't help but pick it up for it looks really good. I turned it over after I got home and it sounds like one or more cylinders are misfiring. I know what this can be caused by but I don't know how to find witch cylinder(s) are/is the problem. Any ideas or tips?
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
This last weekend I bought a used 1979 and the seller said it just won't run well. At 3000$ I couldn't help but pick it up for it looks really good. I turned it over after I got home and it sounds like one or more cylinders are misfiring. I know what this can be caused by but I don't know how to find witch cylinder(s) are/is the problem. Any ideas or tips?
You can also pull the spark plugs to see which one is not firing. If I did this, I would probably put new ones back in. The misfiring could be a bad plug. If you do have a bad plug, you need to investigate how it got that way. Or, it could be a compression problem. Or.........
Thread Starter
2nd Gear
Joined: May 2016
Posts: 2
Likes: 0
Loosen the plug wires at the cap, raise up the idle rpm slightly so it doesn't stall on you. Pull the plug wires one at a time to find out which cylinder does not make much of a difference with the rpm. Be careful with the plug wires, the spark can jump right up a pair of pliers. Use a plastic plug wire puller or wear gloves.
You can also pull the spark plugs to see which one is not firing. If I did this, I would probably put new ones back in. The misfiring could be a bad plug. If you do have a bad plug, you need to investigate how it got that way. Or, it could be a compression problem. Or.........
You can also pull the spark plugs to see which one is not firing. If I did this, I would probably put new ones back in. The misfiring could be a bad plug. If you do have a bad plug, you need to investigate how it got that way. Or, it could be a compression problem. Or.........
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Melting Slicks
Joined: Apr 2002
Posts: 2,337
Likes: 14
From: Norfolk VA
this last weekend i bought a used 1979 and the seller said it just won't run well. At 3000$ i couldn't help but pick it up for it looks really good. I turned it over after i got home and it sounds like one or more cylinders are misfiring. I know what this can be caused by but i don't know how to find witch cylinder(s) are/is the problem. Any ideas or tips?
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
On my drag car (that uses headers) I always bring along my laser temp sensor and just point it to the header on each cylinder. It's always very obvious which cylinder is not firing. And the best part about it is you don't even have to get your hands dirty. I'm not sure how it would work on stock manifolds though, never tried it.
Last edited by htown81vette; May 16, 2016 at 10:03 PM. Reason: spelling
Le Mans Master
Joined: May 2007
Posts: 5,025
Likes: 1,120
From: North tonawanda NY
same here... I was going to ask where one could go to get a new one 
Sounds like an awesome deal! ... I paid around 3k for mine and everything needed serious attention... 4 years later and the interior, engine , exhaust and bodywork is pretty much done... off this week to complete it and hopefully shoot the primer and paint it before july... in hindsight it would have been nice to buy one that needed less work.
Sounds like an awesome deal! ... I paid around 3k for mine and everything needed serious attention... 4 years later and the interior, engine , exhaust and bodywork is pretty much done... off this week to complete it and hopefully shoot the primer and paint it before july... in hindsight it would have been nice to buy one that needed less work.
Last edited by augiedoggy; May 17, 2016 at 09:21 AM.
Melting Slicks
Joined: Sep 2010
Posts: 2,413
Likes: 59
From: Emerald Isle NC
A timing light can be used to find the missing cylinders as well. Just move the pickup from plug to plug and look for erratic (or nonexistent) flashing from the light. If any are found, pull and read plugs, ring out cables, etc.
Carter
Carter
Pro
Joined: Feb 2012
Posts: 577
Likes: 6
Fouled plugs isn't usually random. It's typically a symptom of a bigger problem. What color were the ends when you pulled them? Fouling is caused by any number of fluid sources. Rich mixture, oil blowing by the rings, or coolant from a bad head gasket. All can be checked but you need to figure out what fouled the plugs to begin with.
, post pics.
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
Welcome to the Corvette Forum and good luck with your new acquisition. Post some pictures when you get a chance, we love pictures here!
GUSTO
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
All good tips
A common one is to mix up 5 and 7 on the cap
Done it a few times. will start and seem to run ok but not right.
Ditto on looking at the bad plug then find out why it fouled something else is going on that made it that way
A common one is to mix up 5 and 7 on the cap
Done it a few times. will start and seem to run ok but not right.
Ditto on looking at the bad plug then find out why it fouled something else is going on that made it that way
Last edited by cv67; May 18, 2016 at 12:54 PM.
