1995 Chevy Lumina

1995 CHEVROLET LUMINA
316,000 MILES • 6 CYL • 2WD • AUTOMATIC
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IAN MCDIARMID
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My car began running rough last week. NO CEL. It felt as though a plug wire was missing. I did the head gaskets and lower intake gaskets last November. Here`s a list of things I`ve done this past week with NO change in condition:
New plugs and wires. Checked coil packs by replacing with 3 known good packs. Checked for good spark. Checked compression. All cylinders were 180 to 190 lbs. Checked fuel pressure. Changed fuel filter, removed rocker covers and checked for missing or bent pushrod. Removed fuel injectors and tested for spray. Had them serviced/cleaned at a GM dealer. Dealer found cylinders 1 and 3 not firing though lots of spark. New fuel injectors on cylinders 1 and 3. Changed left head with refurbished head. New head gaskets and lower intake gaskets.
What am I missing? The engine visibly shakes. Is it possible the timing chain jumped a couple of teeth??
Thanks,

Ian
May 25, 2009 at 2:20 AM
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DOCFIXIT
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Hi
Engine a 3.8L? Was head replaced after dealer found 1-3 dead? are 1-3 still dead? Would you remove all plugs and run another comp. test and post all cylinder results?
Let me know
Thanks for donate
May 25, 2009 at 12:17 PM
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IAN MCDIARMID
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It`s a 3.1. No, dealer thought 1 and 3 were dead. Then I changed heads. Ran compression again today. In order from cylinder 1 to 6: 188, 190, 185, 190, 190 and 165. After checking fuel injectors/spark again today, I`m finding that cylinder 6 is the culprit after all. If I remove that cylinders wire there is NO change in engine performance. While checking compression on that cylinder, the first compression stroke results in a pressure of 115psi, then up to 165 on subsequent compression strokes. Adding engine oil to the cylinder prior to test does NOT change results, so I`m leaning towards either valves or craked/warped head and I`m tearing the motor down as we speak to have a look at the valves. This cylinder has a new piston and ring set as of last November...65 000kms ago. No problems. It also has a used/refurbished head. I have another refurbished head I will install on the right side of the motor.
Thanks for your reply. This is a taxi....time is $$$!

Ian
May 25, 2009 at 6:56 PM
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DOCFIXIT
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Your diagnosis is right on think you will find exhaust valve burnt. Good luck hope you get the money maker back on road soon.
May 26, 2009 at 11:27 AM
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IAN MCDIARMID
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Well, unfortunately the problem has not been solved. I changed the R.S. head with a refurb and new gaskets and I`m still missing on cylinder 6. I looked at the cam lobes and didn`t see anything...the valves open and close completely. I tried another coil pack as well and no change. While I had everything apart, I put the best/newest injector on cylinder 6. What are the symptoms of a jumped timing chain????
May 26, 2009 at 5:45 PM
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DOCFIXIT
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Compression the same? plug does fire? inj does spray?
Try this just to make sure no codes find DLC under dash ground terminal B top row second from right.
Count flashes , flash flash pause flash = 21
May 27, 2009 at 12:05 PM
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IAN MCDIARMID
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One last question. No codes. Compression still around 165 on cylinder 6. Have you ever heard of a lifter 'collapsing' under load? Someone suggested that a lifter could possibly collapse under load. This might be a reason I can`t detect it while manually turning the crank. Basically the lifter loses pressure once the engine is running. Heard of this???

Thanks. I`ll leave you alone now!


Ian
Jun 1, 2009 at 1:40 AM
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DOCFIXIT
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Hi
Yes a lifter collaps is possible but you should hear a tapping noise. Also if it was it would be noticable on compression test. I am sure you do but are push rods in corerectly? Where is EGR on this engine? Is it on a runner on throttle body?
Jun 1, 2009 at 1:40 PM
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IAN MCDIARMID
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EGR is on the edge of upper intake. No real tapping noise. Same symptoms even with refurb. head, that`s why I was thinking lifters....the only thing that is the same is the compression. But, I`m assuming that the rings wearing out.
Thanks for all your time. I`ll recheck electrical to the injector, but otherwise I guess I`m looking at a motor....

Thanks again,

Ian
Jun 1, 2009 at 3:17 PM
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