Waking the baby up

[chrisj6]

Ok, so just over the past few days I have managed to get in my new ACDelco Iridium plugs, MSD 8.5mm plug wires, new Bosch O2 sensors, and cleaned the EGR valve. I ordered the block off plates so the EGR wont be there much longer.

Even after all this it seems the truck still gets a bit of high RPM and WOT pinging, and under normal accelerating its just not pulling like it did when I first got the 93 tune from Allen. Do you guys think this could be false knock from the 99 PCM, or something else I need to look for.

Thanks,
Chris

[RedHeartbeat]

Are you running 93 octane? Have you considered that maybe your MAF sensor is bad? Maybe you can borrow someone's MAF and trade it out for yours to see if you still have the ping. If you have modified the intake at all you could affect the MAF readings and knock/ping could occur.

[chrisj6]

Actually the MAF is brand new, I had descreened the old one and was getting alot of ping, so I went back with brand spankin new screened ACDelco one and had Allen alter the tune for it. And yes, I am running 93 octane.

Chris

[RedHeartbeat]

Do you have a lot of piston "slap"? The knock sensors might interpret the noise as a knock. How many miles on the cam chain? May be stretched and retarding the valve timing. Does your engine have the timing chain idler installed? Timing chain rubbing against it might send harmonics to the sensors. I also have read of people running a power pulley that caused a lot of false knock. Do you have any knocking or vibrations somewhere in the drivetrain? I have heard of a cracked flex plate causing a lot of knock retard, also. It will sound a lot like a rod knocking. Just tossing a lot of things out here, may sound stupid but it's points to ponder. I think Kinjo will want you to check your thrust end play on you crankshaft.

[chrisj6]

I am acutally going to take it to the Stealership in the morning, along with it I am taking a list of do not touch! If they touch the PCM someone is gettin shot! EGR is going bye bye tomorrow anyways, and if they say anything about no cats causing the problem, i'll just leave.

Not sure what to expect, just letting them check things out I guess, I do have a small leak now from the passenger side of the engine comparment, sounds like it is coming from the back of the motor. I'm thinking either a head or intake gasket leak or vacuum leak somewhere.

Chris

[RedHeartbeat]

Have you had the LTFT long term fuel trims checked to see if you are getting enough fuel? You probably need more fuel with the cats gone, same as if you had installed headers. Is the rear O2 sensor disabled or are you using a simulator? How about fuel pressure. Have you checked it at idle as well as under a load? I don't remember if the fuel pressure is supposed to be maintained at 53 or 58 lbs at all times. if you drop off pressure under load, your pump is weak. The PCM compensates for richening the fuel mixture under acceleration or low vacuum situations. That is up to a point. I believe the fuel trims max out at 25 and if you're still lean it won't go any further than that. I'm sure you've already replaced the fuel filter since you've been fighting this for a while. If you have a blown head gasket, that's most likely you main problem. Believe it or not, the knock sensors have been known to hear a blown head or exhaust gasket.

[chrisj6]

yeah, I guess I will find out tomorrow, Allen just sent out a retune with a little richer mixture and he smoothed out the timing tables, we'll see what happens.

Oh and he also sent a couple Nelson performance and LS1truck stickers, thats good for at least 20hp right?

Chris

[RedHeartbeat]

That will keep the rice in the bag!