Hi everyone, I hate posting on a forum asking for help without contributing first but I'm kind of in a bind here. My girlfriend drives a 2001 2dr 4x4 blazer. A little over a month ago the heater stopped blowing out hot air so she took it in and they had to replace the lower intake manifold gasket. Shortly after that she started having problems when driving at interstate speed where the engine rpms would skip around between 1800-3000 rpms. It only happened on the interstate and for some reason she decided to not tell me about it.... Finally it got so bad that she wasn't able to drive it anymore and I had to drive it to my mechanic. I had to two foot it because if the rpm's were allowed to settle the engine would die. I also had a hard time getting the vehicle up to speed, the rpm's jumped around between 1500 and 2500 but the engine felt really bogged down. Going up hill the I could barely hit 15mph. The check engine light was on and the engine was throwing codes for the MAF and Relearn crank sensor. My mechanic replaced the MAF (helped nothing) and relearned the crank sensor (also did nothing) but the engine still runs very rough. We had a transmission shop check out the tranny but nothing is wrong with it. I had to take it to another mechanic and so far he has replaced the distributor cap and rotors, the spark plug wires, and the spark plugs themselves. He called her tonight when she was supposed to pick it up and told her that although the engine runs better it still isn't fixed and he thinks he needs to replace the computer with a blank one because he thinks the computer might have gotten fried. Since I have no idea what goes on under the hood with a chevy blazer, and she is about at the end of her bank account with the repairs that have already gone on I figured I would ask on here before she had to pay for a new computer. Any help or ideas would be greatly appreciated. I tried to be as specific as possible but if you have any questions please ask. Thank you in advance for any and all help.

Jon

 

If a relearn procedure did not help, then this could be a problem with the actual timing of the engine. It is possible that the timing chain has stretched to a point where the PCM can no longer keep the appropriate timing. I have also seen the gear on the bottom of the distributor crack, causing the distributor to be out of time. This can also cause CKP/CMP correlation error code.

 

First, thank you for the fast reply swartlkk. Wouldn't the distributor gear have been replaced with the distributor? If so, I would think any timing issues would have been cleared up then. Would the vehicle throw a code if the timing chain was stretched too far, or are all the problems it is having a common result of the timing chain being stretched?

EDIT: Can I assume that replacing the computer won't fix the problem? I have had quite a few cars, and quite a few problems with most of them, but have never had to replace a computer. I wouldn't guess that a 7 year old vehicle would need a computer replaced.

 

From your post, you stated that one of the mechanics that looked at it replaced the distributor cap and rotor. The gear I am referring to is located on the bottom of the distributor itself and is what gets driven by the gear on the back of the camshaft.

If you have a persistent P1345 code (CKP/CMP correlation error) that is not cleared up by a CASE learn (also called crank position variation learn), it is more than likely that one of the components that controls the timing, be it valve/spark (timing chain) or just spark (distributor gear). A compression check may help to rule out the timing chain, but may not give definitive results if the chain is only stretched.

 

Back again, I wanted to clear this post up so anyone searching will know what happened. When the intake manifold gasket blew, coolant leaked into the crankcase. The crankshaft now has some wobble to it (crankwalk?) and hits the crank sensor, which is what started throwing some of the codes to begin with. After fixing everything else that was wrong with the vehicle our mechanic was able to raise the crank sensor to keep the crankshaft from hitting it, and the vehicle now drives alot better. However, with the crankshaft wobbling I know it is only going to be a matter of time before the engine needs rebuilt. Thank you swartlkk for the help when I originally posted, and I now suppose I'll be a regular lurker here as I try to find my gf an engine to rebuild.

 

Wow.. If your crank is moving around enough to cause the reluctor ring to contact the CKP sensor, you better find a new motor quick! That is a lot of movement.