Mad Customs

[stutaeng]

A sign?

#8 spark plug is dark all around. 2,4,6 and 3 have some light areas. (I didn't pull 1,5, and 7.) Perhaps a weak coil?

You must be registered for see images attach

Um, I can't really make out which is which, but easy enough to swap coil packs on these!

 

[Supercharged111]

I'm just frustrated. We are only getting a few hours per week to work on it, and I'm nearing my limits as a shadetree mechanic.

Have you tried cleaning the MAF? Is it the same one that's in the tune? I.E. was the tune baked around an LS6 MAF and you are running an older MAF like the GMT400 got? The order of tuning starts with the correct injector flow values. Next, if all is mechanically sound, you tune MAF and VE. I think in HPT you do them separately, but EFILive has a way to tune both with a single log and it's slick. If I were you, I'd capture a log of misfire activity on all 8 individual cylinders to help narrow down any potential issues. You don't want to pay labor to find out a coil/wire or injector is being flaky.

 

[0xDEADBEEF]

Have you tried cleaning the MAF? Is it the same one that's in the tune? I.E. was the tune baked around an LS6 MAF and you are running an older MAF like the GMT400 got? The order of tuning starts with the correct injector flow values. Next, if all is mechanically sound, you tune MAF and VE. I think in HPT you do them separately, but EFILive has a way to tune both with a single log and it's slick. If I were you, I'd capture a log of misfire activity on all 8 individual cylinders to help narrow down any potential issues. You don't want to pay labor to find out a coil/wire or injector is being flaky.

It's a brand new MAF for a 2001 Silverado purchased from Rock Auto. It's a Delphi I think. New stock AC Delco injectors.

The tune that works is a 2001 LM7 tune with the MAF set to fail so that it runs in speed density. It works pretty well like that actually with balanced banks and O2s functioning normally. If I enable the MAF the passenger side bank eventually maxes out the fuel trims and it runs like crap. The other side is fine. There are no misfires in the log.

I know I need to tune the MAF and VE tables, but I don't think I can proceed from here. I do have wideband O2 that I haven't installed yet.

 

[Supercharged111]

It's a brand new MAF for a 2001 Silverado purchased from Rock Auto. It's a Delphi I think. New stock AC Delco injectors.

The tune that works is a 2001 LM7 tune with the MAF set to fail so that it runs in speed density. It works pretty well like that actually with balanced banks and O2s functioning normally. If I enable the MAF the passenger side bank eventually maxes out the fuel trims and it runs like crap. The other side is fine. There are no misfires in the log.

I know I need to tune the MAF and VE tables, but I don't think I can proceed from here. I do have wideband O2 that I haven't installed yet.

Sounds like the MAF and tune match, but even if they didn't you can tune for that. Do the injectors and tune match? I know you said they're stock, stock for LM7 stock? Have you measured fuel pressure? You wouldn't want to go tuning if pressure was off, that'd mess everything else up. Maybe ohm from the MAF all the way back to the other end and jiggle the harness around? Those pins would still be in their original spot, so I don't see something of that nature being the issue.

 

[0xDEADBEEF]

Sounds like the MAF and tune match, but even if they didn't you can tune for that. Do the injectors and tune match? I know you said they're stock, stock for LM7 stock? Have you measured fuel pressure? You wouldn't want to go tuning if pressure was off, that'd mess everything else up. Maybe ohm from the MAF all the way back to the other end and jiggle the harness around? Those pins would still be in their original spot, so I don't see something of that nature being the issue.

The injectors should be stock, I did buy them off eBay so it's hard to say for sure other than the part number is correct. Fuel pressure is 62 psi per my gauge. It's definitely not low.

 

[Supercharged111]

The injectors should be stock, I did buy them off eBay so it's hard to say for sure other than the part number is correct. Fuel pressure is 62 psi per my gauge. It's definitely not low.

So if you can figure out what's mechanically wrong with the MAF deal, you'll be ready to tune that. In the meantime I don't see why you couldn't start on VE. The trims were all good values, right? I don't think taming the LS6 cam is going to be a very tall order. In my C5Z Corvette, the rev limit is 6600. You should definitely start no lower than that once the wideband comes in.

 

[0xDEADBEEF]

So if you can figure out what's mechanically wrong with the MAF deal, you'll be ready to tune that. In the meantime I don't see why you couldn't start on VE. The trims were all good values, right? I don't think taming the LS6 cam is going to be a very tall order. In my C5Z Corvette, the rev limit is 6600. You should definitely start no lower than that once the wideband comes in.

The other tune I am working on I cribbed from an 04 C5 Z06. I copied the VE, spark and idle tables. It should be a decent starting place because it should be a little on the fat side (5.7 vs 5.3) and would just need shaved down.

I agree the cam is pretty tame compared to what else is out there. I really think it should run with a stock LM7 tune though.

I appreciate your help, BTW.

 

[Supercharged111]

The other tune I am working on I cribbed from an 04 C5 Z06. I copied the VE, spark and idle tables. It should be a decent starting place because it should be a little on the fat side (5.7 vs 5.3) and would just need shaved down.

I agree the cam is pretty tame compared to what else is out there. I really think it should run with a stock LM7 tune though.

I appreciate your help, BTW.

If your displacement states 5.3, then your VE shouldn't be as far off. I would start with a MAF table that most closely matches what you have in the truck, but if I'm understanding correctly you have just that. You also have less compression, so even the more aggressive LS6 spark map would still be a good starting point. I'm leaning toward something mechanical/electrical (non-tune related) being the MAF problem based on what I'm reading.

 

[0xDEADBEEF]

If your displacement states 5.3, then your VE shouldn't be as far off. I would start with a MAF table that most closely matches what you have in the truck, but if I'm understanding correctly you have just that. You also have less compression, so even the more aggressive LS6 spark map would still be a good starting point. I'm leaning toward something mechanical/electrical (non-tune related) being the MAF problem based on what I'm reading.

The heads were actually milled so it's a little bit closer than a stock 5.3 would be. The cylinder volume is correct for a 5.3 in the tune.

 

[0xDEADBEEF]

Y'all aren't going to believe this, or maybe you will ...

I swapped the coil packs from side to side, loaded the cribbed tune with MAF enabled, and once it got some heat in the engine it ran perfect. I let it idle a good while and everything was normal. Drove it around the neighborhood for 30 minutes and it's just a normal driving truck. Not only that but the fuel trims are spot on.

The only thing it probably needs some help with is cold start and the idle in drive is a touch high. I never gave more than half throttle so it might need something there too.

I have to think something with the damned harness was the culprit. For whatever reason it makes a better connection this way. We'll see if it stays this way.