Was replacing the timing chain cover very hard? Any advice on doing it? Mine is leaking and I'd like to address it some day. Knowing that the relearn for the crank will work is nice to know!!

 

I have "heard" (emphasis on "heard") of a relearn fixing an intermittent fish bite misfire though I can't remember ever running into this myself. Though there is no reported misfire check out the attached step #4 (note the explanation of #4 at top of page).

Captain Hook used to state "The truck will run, but it will not run optimally without the relearn".

That all being said, I agree with you Les. I kinda don't think the learn will end the issue Lanny is describing. I could be wrong.

The description of coming off the highway to town and idle problems sounds more related to an idle air control issue. Note I am not saying there is necessarily a problem with the IAC valve itself. When driving, on decel (there's that word again ), like coming down a hill, the VCM/ECM is setting up the IAC for the counts it should be at when it's time to take off from a stop. Of course the VCM is getting its data from other sensors. I picture it as, for example, if the ECT sensor is off by a bit, then based off the tune map in the VCM that can throw off where the IAC should be at at idle. That's just an example I made up. Scanner Danner has a great video that is a much better explanation. I think it's one of his free ones and I'll try to find it.

I completely agree and you may find Lanny that you will get a real P030X code.

 

Here's the video I referenced above:

 

Christine: your question, was replacing the timing cover hard to do?.....yes it is on a 4wd, probably much easier on a 2wd. Hints......have someone else do it.......
The main issue is the large gap in the timing cover for the oil pan gasket....this has to be filled with RTV or it will just leak. To replace the timing cover, I say the oil pan has to come off so as to clean out all the old RTV. To get the oil pan off the front diff has to come out. Which requires the front axles to be removed. Which requires separating the upper ball joints at least, tie rod ends, or guess you could just remove the front spindles. Oh and of course the coolant has to be drained, radiator removed, fan removed, coolant pump removed, starter removed, front shocks removed. Then the oil pan can be dropped, then the front cover.

Now back to CKP relearn. As I stated way up at the beginning, I was expecting to get a SES lite after replacing the timing cover but did not. But since the misfires I felt when stopped, trans in D, foot on brake only began after the timing cover replacement, I just thought that somehow the CKP sensor valves were close but not close enough when the engine was ran for a length of time....so that is why I thought I should do the CKP relearn as it was likely the cause of the misfires. Perhaps this is wrong.

I drove today for the first time since doing the relearn, but not for any great amount of time, had no misfires, no SES lite either.
Guess time will tell if I actually have another issue.
Keep the discussion going.....always willing to learn more.

 

Hey Lanny,
Was curious if you still have no misfires and/or no rough idle coming off the highway since you completed the CKP relearn? Just curious for future reference.

 

So far all is good, but have not had the Blazer on the highway for more than about five minutes since doing the CKP relearn.
I might be able to do a test tomorrow (3/14) though. If I do, I will up-date this posting.

UPDATE:
I was able to get on the highway for a while yesterday, noticed two things: 1. Engine ran better in that it seemed that it was easier to maintain 75mph than before. In fact, I had to lift my right foot a bit every so often as I was going faster. Normally I would stay about 70-73 as above seemed to be pushing the engine hard.
2. Coming off the highway and into stop-n-go traffic I still had a rough idle/misfire, but nowhere near as prevalent as before the CKP relearn. I did install poly engine mounts a couple of years back, so I do feel more vibrations.

Still no SES lite. Have not checked for any pending codes and I will put the ODB 2 scanner back in so I can monitor misfire PIDS on my phone for the next highway trip.

Later