30th t/a

iTrader: (51)

Please, anybody have any ideas what the sam hell this problem is???
I installed new TR6 plugs and a new crank sensor. The car starts perfectly, idles perfectly and cruises perfectly but as soon as I roll into the throttle and rpms hit about 4500-4700, bang!, backfires and stalls going down the road. After about 5-10 seconds, the car starts right up and away I go. I thought for sure it would be the crank sensor but no luck. Thanks
John

A SIDE NOTE: I drove the car last friday night and it ran great....for awhile.
I drove about 45 minutes and then parked. I let it sit for about 1 hour and then drove it another 20 minutes and then it did the back fire and stalled when I jumped on it. After that I drove it home. It has been like that every since.

30th t/a

iTrader: (51)

Another note, two sundays ago, while I was replacing the wires that go to the crank sensor because they have touched the headers and melted a little. As I was soldering the new wires onto the wiring harness one of the new wires touched the positive side of the battery and I heard "zzzzzzzzzz" and saw a little smoke coming off of the battery & wire. could I have fucked up the new wire? how bout the PCM???

Jake@EPP

Sounds like a similar situation ive seen, shoddy wiring caused a car on our dyno to do the EXACT same.

I would suggest getting some fire sleeve and running it over that bundle of wires. Of course i would suggest re-wiring the crank sensor and any other burnt wires.

30th t/a

iTrader: (51)

thanks for the reply. As of now none of the wires are burnt. But like I said, as I was soldering on the new wires, one of them touched the positive side of the battery and you could hear something frying and there was a little smoke. I hope I didnt hurt the PCM. I guess im going to replace the wires I just soldered on to eliminate them from the equation.

Pro Stock John

iTrader: (34)

If the crank wires are messed up, then at WOT you will have problems because the crank sensor will not work properly and the pcm will shut the engine off.

1hotls1

iTrader: (6)

Have you performed a relearn on the Crank position sensor? My problems didn't clear up until this was done. Good luck.

KCFormula

iTrader: (4)

A friend of mine's car has the same problem. We can't find what it is. We have done the crank relear, and tried a different PCM and it still does it. He has had the stock motor rebuilt, could it be a pinched crank sensor wire somewhere?

crafty888

Jeff Schwartz had a similar thing with his Ultima GTR at last year's Silver State. He'd just finished building it the day before the run and hadnt had time to sort it. Turned out to be the electromagnetic field from the alternator interfering with the crank signal. He sheilded the wires and all was good

30th t/a

iTrader: (51)

thanks for the ideas guys.

Im 99% sure this is something that effects the crank sensor. My 1st step is replacing the entire length of the crank sensor wires. clear back to the PCM. Since Ive been cutting them, resodering, and the one touched the battery, I hope the problem is in the wires.

30th t/a

iTrader: (51)

hey guys, I replaced the 3 crank wires and installed my fuel pressure gauge. the car still backfires and shuts down. fuel pressure stays good.

it only shuts down if Im driving it and jumping on the gas. However, I can rev the car to 6000 and it doesnt miss a beat.

another thing I notice is it seems the harder I romp on the gas, the sooner in the rpm band the car will backfire and shut off. If I slowly roll into the throttle, it will go to about 5500 before it backfires and shuts down. If I mash the gas down, it will backfires around 4000 and shut down.

any ideas????

Bad30th

iTrader: (13)

Have you done a CASE/crank position relearn ?

Rob (Bad30th)

67Firebird455

iTrader: (27)

Man, I wish I had some advice other than do a CPS relearn. My TA did that crap and needed a CPS relearn and it was fine.

30th t/a

iTrader: (51)

nope, should I?

Bad30th

iTrader: (13)

If you're not pulling my leg, absolutely.

Anytime you change the crank reluctor wheel (crank), or the sensor you need to do a position relearn so the PCM can accurately predict misfires and predict the position of the crank in the firing cycle.

HPTuners (and most other tuning software) can do it, just follow the directions EXACTLY, including turning the key off for 30 seconds or whatever it says in the help file.

Rob (Bad30th)

30th t/a

iTrader: (51)

haha, I wasnt pulling your leg. thanks, ill give this a try.

30th t/a

iTrader: (51)

Hey guys...I installed my buddys 1999 PCM with his H/C tune into my car. I wanted to see if my car would backfire and shut off with his PCM. Well, the car would "cut out" at the same rpms that my car would backfire and shut down at. BUT using his PCM, the car would not shut off. It would stay running. what the heck?

Bad30th

iTrader: (13)

Did you try the cps relearn yet ?

Rob (Bad30th)

30th t/a

iTrader: (51)

No not yet, I will be next tuesday. I made a appointment with my tuner.
I even got a new wire harness coming but I doubt that will be the problem.

The Dragon

iTrader: (6)

Umm . . . ditto that.

30th t/a

iTrader: (51)

the car shut down before I even touched the crank sensor and then it didnt need a crank relearn. I replaced the crank sensor and the car still shuts down. Ill be suprised if a crank relearn fixes the problem. we find out though.