munn79ta

So my buddy and i just got done with adding prc227 heads and tsp tsunami cam,ls7 lifters,timing chain, ported oil pump,42#'s, racetronix pump,delco 85mm maf,had ls6 intake already, new pushrods, trunion upgrade, everything up top pretty much lol. but initially car wouldnt start then would foul plugs due to not being tuned, we knew it would run rough until we got it done. so we waited another week sent the pcm to tsp... who we ordered all the parts from figured they could get the tune close to what it is suppossed to be b/c its all their components... well we got it back, installed it and now the car will start. but we had to adjust the idle screw to let it idle on its own, no biggie... but tried to drive it and OMG.... backfires like crazy spits sputters bucks. idk what could be the issue.. what has me confused it it will backfire through the intake. and all they say is that the maf might not be working? me personally thought it would be a timing issue but what do i know...every part listed is brand new, i am at a loss on this and my buddy whos car it is feels like he just wasted tons of cash bc all they say is "maybe" the maf isnt working???? any and all input appreciated!!!!!!!! btw car is a 02 z m6 ls1 if that matters

pauls99z28

iTrader: (32)

The reason it fouled out the plugs was it wasnt tuned for bigger injectors.
It could be timing..Did you install cam dot to dot? Degree it? It might be just a hair off..
I assume the delco 85mm maf was tuned in aswell??

munn79ta

yea after we had sent the pcm off we changed the plugs to tr6 gapped at .045. i knew that was y it fouled them way to much fuel and no tune. they tuned it for the maf and everything listed. the maf is a delphi not delco this is all just off the top of my head. and yes i installed it dot to dot. i double checked it so that it was perfect...

munn79ta

anybody????????

ckpitt55

iTrader: (4)

I'm sure you already did it but double check all your ignition coil harnesses, etc.

Did you measure for pushrod length or did you just buy 7.4's? Any excessive valvetrain noise? Not sure how much overlap you have but if you're hanging your intake valves open that could explain some of the backfiring

Otherwise, I'd expect it to be a tuning / sensor issue. Are you throwing any codes? Rear O2's? The mail order tune you got should get you in the ballpark and make it safe to start / run, but if it still isn't running right I think a dyno tune is in order.

munn79ta

at first no we used 7.400 and it didnt have that lopey idle that it should have.... then we realized the heads had a thicker deck surface so we got a pushrod length checker and then ordered 7.450. And texas speed said that length was fine. It made a world of difference. we started it but it would not idle by itself but no backfire through the intake at all. just fall on its face at idle. sent the pcm out to texas speed. got it back now if you just give a rev to like 2k it will backfire through the intake and run like crap....but it will idle perfect after we adjusted the idle screw on the tb??????

Old Geezer

iTrader: (3)

Scan it, log it. W/o some scan data, U R pi$$in in the wind.

munn79ta

scan with ? we dont have **** for scanner only one of the autozone diagnostic code meters. we are afraid to drive it so how am i suppossed to do that???

farmington

iTrader: (14)

you won't need to run it, it will have stored any codes that have come up.

munn79ta

well first off i dont think that my buddy should have to buy any more crap... i mean every part came from texas speed and the pcm should be pretty spot on for the tune if thats the problem?... car didnt backfire like this before we sent the pcm out but wouldnt idle... there has to be more ideas other than oh you need a scanner. ideas to look for something would be more helpful. i figured tsp would have been trying or giving more aid due to the fact he spent an A$$ load of cash there and all they have to say is maybe maf??? we are going to try to go over everything with a fine tooth comb this weekend so any advice would help. also there is no ses light coming on or anything so idk we will have to see......

5.3LJimmy

iTrader: (10)

Have the heads been milled? What is the compressed thickness of the headgasket? My best guess is that the pushrods are too long and the intake valves are not closing fully.

munn79ta

nope heads are the prc 227's that came straight from tsp. i think head gasket is .040???not 100% sure. we had started the car with 7.400 push rods and it had no lope sounded stock idle but was louder... so we measured pushrod length with the checker and came up with 7.450. and tsp verified that tha pushrod would be just fine. so my only guess is that it is firing too soon when the intake valve is not completely shut...that would be timing from the tune correct????

5.3LJimmy

iTrader: (10)

The intake valve closes before the piston gets good into the compression stroke. For the timing to be that far off it would have to be at like 110 degrees advance in the tune. Not only that it would also have to be adjusted in the part throttle/low load area of the table, which most everyone leaves stock.

5.3LJimmy

iTrader: (10)

The fact that it sounded stock is also a bit concerning. 0.050" of pushrod length shouldn't affect it that much. Having the timing chain off a couple of teeth could cause both of these issues. If the cam timing is retarded too far it will not lope as hard due to the exhaust valve open angle.

munn79ta

well before we added the fuel pump and injectors it did lope with the .7450 pushrods....just had a really hard staying at idle. so we changed injectors and pump sent tune off and then ran into this issue but we will be pretty much going through everything tomorrow. and i know 100% that the timing chain is dot to dot i was paranoid about that so i made sure that it was all good bc i didnt want to have to pull the front acc. off and balancer and cover again bc thats not too fun. hopefully we will find its something small somewhere but its not throwing any codes as of last weekend.

Droptopws6

iTrader: (13)

I'm going to say there's an issue with the cam install. Take some photos before you pull the cam out. I've done head/cam swaps on several LSx engines, just taking an educated guess.

Also, a mail order tune will not be spot on, just my opinion.