Pro Stock John

iTrader: (34)

here's a short recap...

last year, i have a problem where the ignition cuts out the car backfires when the unburned fuel hits the tailpipes.

i rewired the crank sensor and installed new crank sensor and it was fine, after trying many things.

it's doing it again.

i swapped sensor, did not cure it.

i solder in new connector for the crank sensor, did not cure.

-i can free rev in neutral with no problem
-i can put the car in 1st and roll up to 5500 no problem, but if i floor it it will cut out.
-in the past i could take 3rd gear up to 6000 and it would not do it but when i floored it would.

i am bummed and very tired from messing with the car all nite.

any ideas? pulled wire from the pcm connector? bad pcm? i have like 20 runs on the car since the last time it happened, and about 10 dyno pulls.

let me know i am going to sleep

Terry Burger

iTrader: (4)

Ground wire or starter wire shorting out.

LS1x2

iTrader: (11)

You sure it's not a fuel problem?
When I had an lt1 car with a stock in tank and NOS inline, the ground for the inline came undone. The car would start ok, rev good in neutral, drive ok, but if I floored it I couldn't rev past 4k. I ran a FP guage to the windshield and taped it up there to see it when I ran and found the problem from there.

Pro Stock John

iTrader: (34)

terry, losing power thru a ground?

formulajoe, i have a pillar fuel pressure gauge, i will look at but my wot fuel pressure typically does not drop below 56psi.

i noticed my voltage is going from 12.7 to 13.0 at idle, does that seem low?

i can stab the gas no problem to like 4000 but more than that and it will lose ignition.

TA2SLOW

John I wouldn't be so sure its an ignition problem either. My friend had the same sounding problem with a old car. Ended up being a bad lifter. Same problems, he could free rev it but once under a load it would back fire out the tail pipes. This motor wouldnt turn past 5000 under load with the bad lifter, but once fixed it turned 6500 all day long.

Shawn

Pro Stock John

iTrader: (34)

Hi Sean, I don't have the bad valve/lifter it pops on accel problem, I have the engine goes completely quiet on all 8 cylinders problem, but my heads will be coming off for some ARE LS6 11.7:1 heads so I can pull the lifter to check.

99 Black Bird T/A

iTrader: (4)

PSJ,

Here's a shot in the dark...

Could the throttle postion sensor be bad?

I've heard of cars reving ok then doing weird things, then being ok when the TPS starts to act up.

What's A-tap saying about TPS voltage?

rich

Hey John. Just a thought maybe a broken valve spring ok at low rpm but when under load and high rpm the valve isn't closing fast enough. just a thought. I have a scanner if you want maybe we could do a snap shot and see what the ecm has to say when the problem occurs. just give me a call or email me

Richie Carbone

iTrader: (3)

Hey Yahoo Serious....try the wires that go from the battery to the starter. When Tim Z28 and I installed the cam in my car 2 1/2 years ago the same thing would happen. It turned out that the wire was burned through from laying against the header and would ground out when the motor torqued over under WOT.
All of the gauges would go nuts and the cluster would light up like a Xmas tree <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

Good luck!

Tim98TA

iTrader: (7)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong>terry, losing power thru a ground?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">As much as I hate too, I have to agree with Terry on this. YES, you can lose power through ground. Remember, the ground completes a circuit. Bad connection, corroded wires, BS like that will make you go nuts till you find it.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong>i noticed my voltage is going from 12.7 to 13.0 at idle, does that seem low?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">You need to have ~13.3v-13.5v.Do you have an overdriven alt pulley? If not, get one.

Tim

Pro Stock John

iTrader: (34)

Did all the cylinders stop firing? I lose ALL SPARK. It's not popping like I have one bad valve or lifter.

I'll start checking the grounds but I might be bringing it to a buddy who has the patience of JOB.

Pro Stock John

iTrader: (34)

I'm going to move this thread into the pcm section.

Also, a good buddy Mike @ Yank mentioned it's his understanding that the pcm needs 13.2 at WOT to work properly, I am seeing 12.7-13.0 so could a bad battery be my problem?

Or... could I have bad plug wires? Thing is the car dies in all 8 cylinders and ONLY under load.