973800CamaroRS

iTrader: (3)

I'm hoping someone else has solved this problem before I finally got my car running and everything seems ok, I take the car to get it tuned and its fine up until 4000 rpms and it breaks up backfires and cracks. Immediately I thought ignition so I replaced Coils, wires, and plugs, same issues. After that it must be fuel because a/f ratios goes nuts right at 4000. clean all fuel lines, injectors, new fuel filter. Same issues still At this point I am replacing sensors, crank sensor, tps sensor. Still same issues car is smooth up until 4000. revs and drives smooth until that point. rev limiter is set at 7500 so its not that. I am thinking map or cam sensor but its just so weird to me. Fuel pressure is fine when this happens. It was driven 10 miles on a rough tune could the 02 sensors be messed up ? even though it idles at a great a/f ratio ? Running out of ideas here.

2xLS1

iTrader: (25)

Where is a datalog of it having the proplem? You said you took it to get tuned. The tuner should have a datalog.

Or you could just keep blindly changing parts with no real diagnosing.

973800CamaroRS

iTrader: (3)

I do not have a tune file nor do I have the program to view it. Tuner said ignition or fuel problem well it seems that is not the case.

98redorangeta

iTrader: (10)

You could try a crank relearn I would think it would set a code for that but I think it limits you to 4000 rpm if it hasn't leaned the crank sensor.

455GTO

iTrader: (18)

I had a similar issue when I swapped in the 403LS2 motor. It would happen at 6300rpms and it had me stuck for about 2 months... I decided to swap in a new crankshaft position sensor in hopes that it would help... Sure enough the misfire issue was fixed and can now rev it to the moon.

If I were you, I'd throw in a new sensor and see if it does the trick. My car never threw a code for a bad sensor so I had no idea what it was...

joecar

If he can't rev it past 4000 rpm he won't be able to do a crank relearn... so that can't be it.

973800CamaroRS

iTrader: (3)

Crank sensor is new, the old one was the reason it wouldn't start.

973800CamaroRS

iTrader: (3)

Low and behold replaced it again tonight and issue is solved. Old one was only a month old.

98redorangeta

iTrader: (10)

Ah I thought it limited rpm and got rid of misfire detection if you didn't do it. It's been a while thanks for the correction.

Glad the issue is cleared up now.

MontecarloDrag

iTrader: (3)

Your tuner should be able to give you a correct diagnostic