fuel deliver, spark or computer related?

[Tahoe03mm]

I've been trying to figure out what is wrong with my 2003 tahoe.

Brief history: I put my lq4 6.0 in last june and it's been running great after getting my blackbear tune. It's got a custom grind cam, lpp long tubes, recently replaced the rocker arms because the stock ones were getting noisy.


My symptoms were it wasn't performing very well at higher rpm's almost like the engine was cutting back due to fuel or ignition I wasn't sure which so tried to do some obvious things.


here's what i've already done to narrow things down:

• cleaned air filter
• replaced plugs and wires
• replaced fuel filter
• put a fuel gauge on it and it didn't drop at all it's at least 50 or so
• seemed like the MAF sensor was acting up so I cleaned it, then wound up replacing it

Now I swapped out the MAF sensor and it ran great for about a minute... ran it up and down the block seemed normal, then started running bad again. (it was cold still when I first took it out) Now basically if I even rev it much at an idle it will try to balance out and die, restart it and it turns over a couple time then fires off.

I'm wondering if it's possibly a pcm issue or worse my cam could be going bad. It just seems like it might be starving for fuel. Driving it around it reminds me of a plugged CAT almost with it's lack of power.

I opened the throttle body it doesn't look too dirty but I didn't pull it off the intake... Wondering if I should check that out too.

 

[bkboatnsleds]

Almost sounds computer related - Does not sound like an easy problem to track down Any check engine lights?

 

[Tahoe03mm]

P101 and p0300 which is MAF circuit and random cylinder missfire.

replacing the MAF got rid of the p0101

 

[bkboatnsleds]

Could a coil pack me going bad?

Saw this :

http://www.fullsizechevy.com/forum/...-problem-my-chevy-c1500-engine-stumbling.html

---------- Post added at 07:35 AM ---------- Previous post was at 07:32 AM ----------

people all over the place on this one..

http://www.gminsidenews.com/forums/f53/p0300-02-tahoe-48282/

 

[Tahoe03mm]

Thanks I'm gonna look into those issues too. I'd like to think it's not the intake because the gaskets are only a year old... But anything is possible.

 

[Tahoe03mm]

swapped out a MAF with a new one and it seemed to run great "normal" when it was cold then after driving it for just a little it started running like crap again. P0300 is still there and I'm trying to narrow it down.
I doubt it's 02 sensors those are only a year old and the back two are tuned out.

checked fuel pressure and i'm getting no less then 50, but it does drop after sitting... is that normal?

Reving it at idle it will try to level out but just dies.

I check out the fuel pressure regulator as someone suggested, pulled off the vacuum line of it and didn't see any fuel coming out it.

The intake gasket is a year old and the new style.

there is not CATs
Any other ideas?