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Old 06-04-2018, 12:02 AM   #1
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Join Date: Mar 2008
Location: Bellvue, CO
Posts: 5
Distributor CMP Offset Issue

I hope someone has a similar issue that can help with a timing the camshaft retard offset (CMP) and aP1345 issue.

I have a 96 K1500 5.7 ... 280000 total miles. It has about 700000 miles on a replacement GM engine. After about 50000 miles there was a slight ping under load or higher RPM. At 60000 miles I was getting random misfire codes under load. Eventually after throwing parts at it with no change ... I did a full tune up. It did get better but still pinging a bit ... but finally read about the Distributor CMP offset and decided to check it with my scanner and it was at -10. I rotated the distributor, but could only get to -4 before it hit the intake manifold. At the same time I did a compression test and all cylinders were sound. It ran a good bit better, ping gone and no more error codes ... well I decided to see if I could move the distributor clockwise a tooth and reset CMP offset closer to zero.

Since I was pulling the stock plastic distributor I sprung for a Summit Racing billet replacement. I set it back one tooth from the original and reset the CMP and now got it to +1 degree ... within the +/- 2 degree window. It started back up straight away and sounded good, but P1345 is set right at start up. It resets and comes back immediately on restart.

I read you need to re-learn the crank/cam, but another place said this is only on 98 an newer. Do I need to take it in and have this done? ... or do I need to move it back a tooth and live with the -4? I am not sure how it got to -10 to begin with ... maybe being off a bit initially and wear over time?

Thanks in advance if anyone can help.
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Old 06-12-2018, 01:03 PM   #2
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Join Date: Jan 2006
Location: Smithfield, VA
Posts: 1,319
Been there........

If you have the ability to do cam offset, you can do the relearn also.

These engines do not like to be positive and mine doesn't like being 0. Always make sure it's negative.

Also this is not causing your ping issue. If you have the OEM plastic intake gaskets, I'll put a month's wages on a bet they are leaking oil. I had that issue once and it pinged like you would not believe. The only thing that helped reduce it until I replaced them was using premium grade fuel.

Once I changed the gasket to the new steel core ones, problem was solved.
99 Z71 (98 body style)
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