plug gap & missfires
On your first question, I do not know if these ignitions were different (weaker)when your car was manufactured, but on my 2005 LS6 I can increase the plug gap substantially above 0.040" with no misfires - at least while the plugs are fresh.
After I re-cleaned the MAF with alcohol there's no change from where I landed.
I don't know if they were necessarily weaker but the car certainly is much older and worn down then your 2005 LS6.
When my converter wouldn't stay locked, the computer would see 30 something misfires at regular driving un-locked and then, when it lock up it went up to like 80 something and un-locked the converter again. So obviously it's been misfiring the whole time but just not enough to tell. Now I'm guessing that gaping the plugs more is causing it to missfire even worse. I realize that it's been stated already that that is an indicator of a larger problem but my point is that I don't know what else would cause such a weak spark other than worn out coil packs. If the timing was off or there was some other tuning issue, wouldn't it be misfiring regardless of the gap?
I don't know if they were necessarily weaker but the car certainly is much older and worn down then your 2005 LS6.
When my converter wouldn't stay locked, the computer would see 30 something misfires at regular driving un-locked and then, when it lock up it went up to like 80 something and un-locked the converter again. So obviously it's been misfiring the whole time but just not enough to tell. Now I'm guessing that gaping the plugs more is causing it to missfire even worse. I realize that it's been stated already that that is an indicator of a larger problem but my point is that I don't know what else would cause such a weak spark other than worn out coil packs. If the timing was off or there was some other tuning issue, wouldn't it be misfiring regardless of the gap?
I just checked and the coils are the same part number for yours and the 2005 LS6 so I assume the ignitions offer the same intensity. (Coils, by the way are about $50.00 a piece.)
You may have an MAF problem now since those wire are pretty sensitive - technically you are not supposed to clean them, but most folks do allright cleaning them carefully with alcohol.
One point made earlier was that perhaps the oil in the intake is causing the misfires. This can happen if enough oil is mixed with air entering the cylinder because it results in the wrong air-to-fuel ratio. How much oil is in the intake?
You may have an MAF problem now since those wire are pretty sensitive - technically you are not supposed to clean them, but most folks do allright cleaning them carefully with alcohol.
One point made earlier was that perhaps the oil in the intake is causing the misfires. This can happen if enough oil is mixed with air entering the cylinder because it results in the wrong air-to-fuel ratio. How much oil is in the intake?
It didn't seem like it was enough to cause misfires just more than I should be getting with a catch can. It was wet around the gaskets & there was a little bit of gunk in the ports.
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Verdad Gallardo At this point I think you have checked the obvious things. Rather than throw parts at it, like coils or an MAF, I would take it to shop that has a GM Tech 2 scanner to see what is going on.
No. Timing varies w/ RPM & g/cyl, among other things. Unplug the MAF & see if it's better. Still find it odd that the problem began w/ the initial re-tune after mods. Could also be false knock. Again, I say to have a different tuner look @ it.
So, if I unplug the MAF and it gets better what does that mean?
The only other place to take my car to have the tune looked at, this guy works at some times. Plus he looks at my car for free for me when I have issues. He is a very competent tuner and has done hundreds of cars in my area, in the past couple years, and has never once had any issues. However, I will contact the local speed shop and see what they could do to help me out.
Last edited by CayenneRedV6; Dec 22, 2010 at 01:32 AM.
I just went out and unplugged the MAF and started it up. I only let it run for a little bit 'cause it's cold and late but, it didn't seem to change anything at all. Was that long enough or do I need to drive it down the street?
Last edited by CayenneRedV6; Dec 22, 2010 at 02:17 AM.
When you unplug the MAF, it should run better if the MAF were the isuue. Since the problem persists, the MAF is OK. You should drive it around the block to confirm. There will be a check engine light that will turn off once the MAF is plugged back in. Other thing is it could be the MAP sensor, but would likely have a constant CEL if it were. It really does seem like a tuning issue.
Wide open throttle should not exceed 26* max timing. I am thinking that the tuner has WOT timing higher. Also, the complete VE, idle & spark tables need to be looked @, among other areas. Have the tuner check for false knock w/ a scan.
Mechanically, check the injectors & coils. Check to see that there is voltage to both from the PCM while running. Unplug each injector & connect 12 volts to each. You should here a click. If clicking, it's OK, as long as it's not gunked up. Coils can be checked w/ an Ohm meter.
If you don't know how to do this. It's OK, just let the person helping you know that these things need to be looked @, among others. Just tell the tuner that it's not a personal thing... you just want another set of eyes to have a look @ the tune. If you want, the HP tuners file can also be downloaded in the tuning section & a number of people can help by evaluating the tune. I have EFILive. So, unfortunately cannot open the HP tuners file.
When all this first started happening I swapped coils out with my tuners car and I was still getting the misfires at WOT. So, I don't think that's the issue. Of course, I could be wrong. I've got the tuner sending me the file tonight and I'll upload it on here as soon as he does. I don't have many tools here where I'm at right now so I don't even have a fuel pressure gauge. I may just end up having to pay someone to figure out what the problem is. The only person I know to talk this out with who knows my car is the tuner so, I'm going to call him tonight after he sends that file and see what he says.
Would y'all not come to the same conclusion I did? If the car was misfiring at WOT and gaping the plugs smaller seemed to solve the issue for about a year? Then the misfires at normal driving got bad enough that the converter wouldn't lock up and it was misfiring at WOT again, granted not as bad as before, wouldn't you assume the same thing I did? That the problem I had when I first did everything had gotten worse?
Oh and now I've got another unrelated issue. I'm pouring coolant out from around the water pump. So, I have to get that fixed. There's no coolant in the oil or anything so it's just the pump.....hopefully. The best part is, I had the coolant system flushed over the summer by a shop, I never have other people work on my car, and it seems as if they put mostly water back in it. I've never had such bad luck with a car.
Would y'all not come to the same conclusion I did? If the car was misfiring at WOT and gaping the plugs smaller seemed to solve the issue for about a year? Then the misfires at normal driving got bad enough that the converter wouldn't lock up and it was misfiring at WOT again, granted not as bad as before, wouldn't you assume the same thing I did? That the problem I had when I first did everything had gotten worse?
Oh and now I've got another unrelated issue. I'm pouring coolant out from around the water pump. So, I have to get that fixed. There's no coolant in the oil or anything so it's just the pump.....hopefully. The best part is, I had the coolant system flushed over the summer by a shop, I never have other people work on my car, and it seems as if they put mostly water back in it. I've never had such bad luck with a car.
You mentioned that it could be the MAP sensor but the CEL would most likely be constant. The MAP sensor doesn't exactly fit tightly in its little hole and it had oil on it. Do you know what would happen if it was good but getting inaccurate readings? I don't know how the MAP sensor affects how the car runs.