1996 Saturn SC1 Misfire After Head Repair

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WICKERW
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My son has a 96 Saturn SC1 with 80,000 miles. It started drinking lots of oil and leaking it out of the radiator overflow tank. No coolant was in the engine oil. I have read that Saturn had a defect in the manufacture of these heads and this problem is common. We have replaced the cracked cylinder head and flushed the cooling system several times. The car never ran hot and it should run good now but it has a bad misfire. The trouble code is P0300, multicylinder misfire. My question is. Did we get the timing chain back on right? I thought we did but I can't seem to find any other reason for it to misfire. Would the car run at all if I was one tooth off on the chain? Is there any way to check it without taking it back apart? OK that was several questions but I need a little help with this one. Any suggestions? Thanks,
Apr 19, 2006 at 12:34 PM
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PEPPERMRJ
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I doubt that you are off as far as the timing chain goes. Check the plug wires for proper sequence. I would also look at the intake manifold and hoses for vacuum leaks.
Apr 20, 2006 at 12:25 PM
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WICKERW
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Thanks Pepper. I found my problem. I new i was getting fuel and all plug wire were in sequence with a blue spark. I decided to check compression before taking it apart again. Guess what, the number four cylinder had zero compression! I had just looked at the top of that piston a few days ago and it did not have a hole in it. Therefore, i new my problem was a valve stuck open. I removed the valve cover and the rocker arm on the intake valve was not lined up correctly on my new head. I tapped it with a hammer and it snapped shut. A few minutes later, the plugs were in, valve cover on and the car runs great. The check engine light went off and my teenager was happy again. Thanks again. :)
Apr 21, 2006 at 3:33 PM
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Suggested Repair

If a multicylinder misfire remains after head replacement, check compression before assuming the timing chain is off. On this car, cylinder 4 had no compression because the intake rocker was not seated correctly and the valve stayed open. Realign the rocker so the valve closes, then recheck. Also verify plug-wire order and inspect the intake manifold and hoses for vacuum leaks.

Conversation Summary

A 1996 Saturn SC1 was using oil and leaking it from the radiator overflow. After the cracked cylinder head was replaced and the cooling system flushed, it had a P0300 multicylinder misfire. The owner asked whether the timing chain might be one tooth off. An expert doubted a timing error and suggested checking plug-wire order and looking for vacuum leaks. Compression testing then showed zero compression in cylinder 4. The intake rocker on the new head was misaligned, leaving the valve open. After the rocker was tapped into place and the valve closed, the misfire stopped and the check-engine light went out.

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