Me and some friends just got done removing a knocking 6.0 for a 5.3 in my 02 denali. Anyways when we started it, it went straight to 4k rpms and was bouncing off the rev limiter. I did not have my foot on the gas at all and the TB was not even open when doing this. So I tried flooring it and letting off to see if that would help. Nope, not one bit.

It ended up tripping a reduced engine power light and pretty much shut the engine off.

So anyone ever had a similar issue? I'm using the 6.0 lq4 PCM to run the 5.3. According to 2 different tuning places the 6.0 PCM should run the 5.3 just about perfectly. We also installed all the 6.0 sensors bc it "was" a running engine. My thought is that it has something to do with the throttle body, but no real way to test a DBW setup is there? Anyone out there had this happen to them?

 

Your Denali is mad at you for putting a 5.3 in it.
I'm not sure why its doing it, hopefully someone here can help you out.

 

lol that is prob true, but the 5.3's happen to be alot cheaper. I thought large vacuum leak, and found that the EGR was leaking. Put a plug in it to seal it off. Either way I think I would hear a vacuum leak that was this bad.

 

I would not run the 6.0 tune in a 5.3. I would assume that is your problem right there. Is this a cable driven TB, or wire? I think they might have offered both around that year.

 

the denali is DBW

 

It is DBW. The 5.3 was a DBC but I changed all the sensors and the whole intake and TB over to the 5.3 from the 6.0.

I called Speartech, and PCM for less to ask about the 6.0 tune running the 5.3. Both of them told me it should run just fine on the 6.0 PCM tune. I was thinking the same thing until 2 reputable tuners told me this.

 

Had the same issue when going from the a 5.3 to 6.0.... the gaskets for the intake were blown and not seating and it was vacuming from there. replaced the intake gaskets and it was fixed... Mine would rev up and bounce off the rev limiter. The throttlebody wouldnt open. Thought it was the tune also.....

 

Has to be a massive vacuum leak, and I agree on the intake gaskets.

 

Ya, they didn't look great. Guess I'll buy some new gaskets and make sure everything seals. Glad to see someone else that has had this same issue.

 

UPDATE:

Well messed with it some more last night. Got some carb cleaner and sprayed it all over the intake while it was running. It did not change anything, so I'm thinking it's not a vacuum leak anymore. We checked the codes it threw. It was a P1514 and some maf codes, and something about air before TB. Can't remember exactly.

So we then changed out the MAF with a known good one, and it still messed up. Only thing I could think now is either wiring at TB, or the whole TB needs to be replaced.