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Old 09-03-2009, 10:31 PM   #1
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Default This one had us stratching our heads

OK, been working on a red GTP for a while now. It'* a fast car, low 12s in the 1/4

Last week I get a text saying I blew my motor. I'm like what? I was working on it yesterday and everything was fine. He said I drove home but it'* running rough. Well, then you didn't blow the engine. After many text messages I determined the engine was not blown but running rough. I gave a few suggestions for him to check, including pulling the valve covers and inspecting the valve train.

Monday he comes over and we start poking around. We changed the MAF last week so I said put the old one back, no change. Hmm, feels like a miss, but nothing shows up on the scans. Only odd thing is the LTFT was -10 to -13. Why so rich I think. Hmm, perhaps a cylinder isn't firing. We test the coils, find nothing but swap them out anyways. No change. Test the plug wires, and swap them out just for giggles, no change.

By this point another friend showed up to help. Now 3 of us trying to fix this problem. By this point we figured out it'* not the ignition system. But we can smell gas in the exhaust.

OK, pull the plugs. #5 is black, the rest look good. So 5 is the problem, this helps. But why? We decided to pull the injectors, perhaps #5 is stuck open. We move it to #1 and swap the plugs as well. Start, and no change. Pull the plugs again and #5 is starting to turn black.

OK, it'* not ignition, and it'* not the plug or injector. I say there'* only one thing left and that'* a mechanical. Out comes the compression tester. Everything checks out, including #5 By this time it'* getting late. Not a clue what'* going on here.

Well, finally broke down and pulled the valve cover.
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One broken spring. The way it broke the valve still closes, this is why the compression test was good. But when running I'm guessing the valve started to float. What a pain.
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Old 09-04-2009, 09:42 AM   #2
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But doesn't it feel good when you finally find it? I know it does for me, but it is usually you giving me the tips to get there.
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Old 09-04-2009, 11:26 AM   #3
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What are the odds of that happening? Way to keep at it and find the problem.
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Old 09-04-2009, 01:26 PM   #4
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This is one of the reasons why when people try to help pin point the problems for forum members and others, you have to work through a logical process to rule out suspected issues. The last place I would have looked was the valve train, and certainly the one of the last places to check on your way to solving the problem.

Thanks for sharing Dan. I'm sure you are giddy as a barbarian after a successful pillage, plunder and killing spree for finding this.
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