Need help ASAP, 5 cylinders misfiring after timing chain install
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Joined: Mar 2003
Posts: 112
From: East TX
Need help ASAP, 5 cylinders misfiring after timing chain install
I just installed the lt4 ED timing chain and my engine is misfiring like crazy. I scanned it and it said the# 4,5,6,7, and 8 cylinders are all misfiring. I also installed a new optispark and new plugs at the same time. Some people are telling me it needs new wires, but it was working fine before I tore it apart. I'm 99% sure I installed the timing chain right, but if not, could the timing chain being off 1 tooth cause only 5 cylinders to misfire? I assumed that if it ran at all, all 8 cylinders would be misfiring. Please help, I'm stuck! Thanks...
<edit>
also, the SES light is flashing if that means anything...
<edit>
also, the SES light is flashing if that means anything...
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Joined: May 2003
Posts: 2,275
Thread Starter
Registered User
Joined: Mar 2003
Posts: 112
From: East TX
I've checked all the wiring several times, everything is right. I tore it apart again and checked the timing chain, it's right too. I pulled some of the plugs off of the injectors and on three of them there is no change in the idle speed. Is there anything that could cause the pcm to screw up when the timing chain breaks? I have no idea what else it could be... anyone have any suggestions? Thanks...
Thread Starter
Registered User
Joined: Mar 2003
Posts: 112
From: East TX
Yes, the stock chain & gears broke.
Yes, it's running very rough. It's hard just to keep it idling. Yes, I did put the reluctor back on. When I got the new timing cover it already had a crank sensor in it so I just used that one. That couldn't be the problem could it? I didn't think the crank sensor could cause any kind of misfiring or anything... Also, someone told me that if I had bent any valves it would be backfiring, but it's not, is that true? I'm in the process of doing a compression check on it. So far, all of the driver side cylinders are fine. I haven't done the other side yet.
Yes, it's running very rough. It's hard just to keep it idling. Yes, I did put the reluctor back on. When I got the new timing cover it already had a crank sensor in it so I just used that one. That couldn't be the problem could it? I didn't think the crank sensor could cause any kind of misfiring or anything... Also, someone told me that if I had bent any valves it would be backfiring, but it's not, is that true? I'm in the process of doing a compression check on it. So far, all of the driver side cylinders are fine. I haven't done the other side yet.
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