| [GMCnet] Engine suddenly running rough [message #172802] |
Sun, 10 June 2012 13:32  |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
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Here is one of those posts looking for a miracle answer. We pulled the coach out Friday night to go to the coast and instead of letting it warm up I thought I’d baby it and let it warm up on the road. Pulling out of our neighborhood to the busy street she coughed, backfired and died. I started the engine and continued (very slowly) my left turn pulling over to the curb to let it warm up.
The engine was now running rough. Once it warmed up we drove to the coast and, though it was still misfiring it drove well. Pulling out a few hours later on the way home I heard a series of backfires as I was trying to accelerate. Still she got us home without issue. The engine is running rough, but it idles, starts and stops without dieseling. I now smell what I think is an NOX like smell from the exhaust.
I thought I’d be brilliant and change the ignition module and spark plugs. I did this and she runs just the same. Upon inspection of the spark plugs I see that #3 is slightly oily, but the rest look good. Here is a picture of the plugs - a complete tune up was performed by Tom Hampton about 15,000 miles ago and the miles driven since the back-fire incident are about 100.
<http://www.gmcmhphotos.com/photos/miscellaneous-stuff/p44496-spark-plugs.html>
<http://www.gmcmhphotos.com/photos/miscellaneous-stuff/p44497-spark-plugs.html>
I’m beginning to think that the backfire jarred the carburetor somehow. I have a Rockwell manifold, so the crossovers are not an issue and it looks like the vacuum lines are okay, but I didn’t give them a thorough inspection. The cap and rotor looked okay, and I just don’t think 15k miles is enough to kill a cap and rotor.
What could I be missing, a burned valve?
Larry Davick
The Mystery Machine
1976(ish) Palm Beach
Fremont, CA
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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