I have a question.

How do you know it was running off the low octane table, do you have tuning software or just the programmer?

Also when you disconnect the battery i believe it resets ALL your trims. With that said if your trims had not relearned fully to compensate for a tune that is off (tune toooo lean), then it would not add the LTFTs (Long Term Fuel trims) to your WOT run, which would cause it to be lean... More than likely you have not had a problem in the past due to learned fuel trims...


Also disconnecting the battery probably reset the adaptive spark tables and they may not have time to relearn either, meaning it is still trying to run off the High octane table... The only way to force it to run on the low octane is fail the MAF....

So you were probably running off the High octane table with a lean tune.....


All that is theoretical(Sp), but it is my .02....

 

I just asumed low octane, but I like your theory. It makes good sense. You explained it a lot better than I could. But can anyone guess whats wrong with it now. I do plan on looking into it after work and through the next couple of days. I just took a quick little drive around my job and I don't notice anything out of the ordinary. No smoke, No sputter, all guages look good, Oil looks good, runs cool, and no service light. The only thing noticeable is on a cold start there is a loud tap that gets quiter after about 20-30 seconds. I'm guessing it's a valve spring. I think that because it's loud at first when the oil is settled up top then as it warms up the oil is coated on everything again. A bent valve would have more issues wouldn't it? I'm just hoping that piston is still ok.

 

has the vacuum pressure changed at idle?

 

Man it sure came out cheaper running midgrade fuel huh..

 

good question, that should tell if you if there is a valve spring problem.

 

Not sure on the vacuum pressure. This all happened last night. I can't really mess with it because I'm at work. I'll fool with it this afternoon and the weekend.

 

do you run a boost/vacuum gauge?

 

I don't have one mounted but I have one I can use. I just never installed it.

 

Whats that #7 spark plug look like?

peace
Hog

 

Ok, I pulled the 4 spark plugs on the drivers side and 3 of them looked good but the one in the back by the firewall looked pretty bad. Ok, it looked real bad. After replacing it, the tapping wasnt as bad. In fact I could barely hear it at all. I got out of work a little late so I ran out of light plus it's pretty cold outside too. I'm off tomorrow so I'll check the other side then. Here's a pic of what it looked like.