Missing at WOT........coil?

[6SENSE]

Checked coil resistance. Is 13.5k~ too high? 11k-13k is what Ive always looked for as good but recall usually falling around high 11's on past tests.
Also checked with Casper's ignition simulator. Dont see spark breaking down at all (tops out at around 8000rpm on tester ).

 

[WarpSpeed]

Could be coil pack.. could be you just need a little more fuel psi... could be a weak altenator..

 

[6SENSE]

O2s are HIGH at WOT, 850s +. One frame on Tlink showed 902! Turned down the alky and theyre still up there. Seems to have more than enough fuel. I know I can stand to turn the fuel psi down a bit (currently at 43), but I dont think thats gonna solve the problem.
I was also thinking of changing plugs (been in for about a year) and tighten gap from .032 down to .030. Just trying not to do too much too quick or I wont know what the problem is.

Oh yeah, voltage didnt fall below 13.3 volts.

 

[SLOW_85]

Oh yeah, voltage didnt fall below 13.3 volts.

Wonder what it is at the fuel pump?
Sounds like maybe your alternator belt is slipping under load. Alt should put
out more the 14 volts. Just another idea.

 

[Lee_Burough]

With that range of O-2, it sounds to me like you have enough fuel and the miss probably isn't a fuel issue....

Plugs, wires, coil, ignition module....MAF would be what I would check. Any Codes?

That Casper's tester is no good....I'll take it off you hands

 

[ALBERTAN]

My Turbo T backfired on me at WOT last week. I started with the plugs and wires. Two of the Magnecore plug wires were faulty and the plugs were gapped at .40 - .45. I haven't gotten on it since replacing everything but it runs noticably better already.

 

[jastrckl]

might be rich miss? a stock o2 sensor isn't exactly crazy accurate, it could be a little rich or a LOT rich. What are the BLM's like? Gap might not be wide enough, should be .035 unless you're boosting enough to blow out the spark you can close it up, but I doubt it.

 

[TurboGN]

6sense, have you ran a separate ground for the coil? Free, couldn't hurt, and has cured many before yours from missing. My new Autolites, gapped to .033, no. 5 cyl was dark compared to the others. Changed all out to new ACs and all was cured. However, most missing/backfire is caused by the coil or module, it doesn't appear the coil is your problem. Good luck, Joel

 

[6SENSE]

Originally posted by lburou
With that range of O-2, it sounds to me like you have enough fuel and the miss probably isn't a fuel issue....

Plugs, wires, coil, ignition module....MAF would be what I would check. Any Codes?

That Casper's tester is no good....I'll take it off you hands

Changing plugs today (and gapping to .030).
Wires are 10mm Magnecore, hope there isnt anything wrong with them. I can test them for resistance right?
Ign Module I bought new from dealer maybe almost 2 years ago. MAF is LT1, which I had another sitting so I already tried that. No codes.
Casper's tester.........

Thanks for the feedback guys.

Just saw your post come through jastrckl. BLMs are good: 120s @ idle, chip locks @128 WOT. Tell me more about gap not being wide enough. I was thinking stronger spark by tightening the gap, or am I backwards? Ive got 3 plugs back in now @ .030, so nows the time to change before I go any further. As far as boost, I was able to tune in a kr free 25psi the other night. It was taking off like a beast, only if it would stay smooth at WOT though . So the car will eventually be under high boost (and alky). Since doing the testing lately though Ive got boost at 19psi.

 

[rob nolan]

Don't feel bad!!! i'm going through the samething. I have replaced everything new you can think of my my car. My car ran great the other day no backfire. Then i took it out again last night and made my first pull and it ran better than the day before. So i thought well lets try it again, then the backfire was back. I have been fighting with this for the last 5 months. I thought i had it nailed down then it comes back. I just ordered a set of MSD 8.5 plug wires today. I just bought a set of the longer plug wires from Red Armstrong about 5 months ago because of the taller valve covers. If you can figure it out let me know what you did.

Rob

 

[jastrckl]

yes the narrower gap means stronger, but it also means that the spark is more 'hidden'. It's sort of all a compromise. If you widen the gap, it might be weaker, but more fuel will be exposed to it. The risk in a wide gap is that the weak spark is easily 'blown out' from things like high boost (I think that has more to do with the electrical resistance somehow changing based on the pressure of the air, but that's above my pay grade). The tight gap and rich condition I could see having issues too though. Since your chip locks the blms at 120 and doesn't just adjust them, I dunno how you would check to see how it's running. have you read the plugs against a chart to see what they show? I recommend you borrow a wideband and see where you really are.

 

[Lee Thompson]

TOO RICH

Start by taking 2 lbs. of fuel out and try. If no detonation, continue to reduce fuel pressure.

 

[fast eddie]

Too rich,I second that

I ran into the same problem when I steeped up with higher flowing injector and a rich condition,and then you throw alky at it.
what cured my problem was turn the alky on at a higher boost level and turned the pump speed down(less alky) and less fuel psi.
Ed

 

[WarpSpeed]

Might be wires too,,, one of my Taylor 10mm wires went, and the car did what you described. Seems the more you remove and install them, the more chance one of them will fail.