so ive got a 95 M6 Z28 it has around 73,000 miles on it, i bought it wrecked and fixed it, ok heres the weird thing the car runs good, seems to idle fine but a lil high around 1100 rpms, but if i go up a hill in 4th or 5th gear and put it to the floor it pops out the intake, it has new plugs, wires, opti, map sensor, iac valve, 4:10 gears,cai, and a programmer and only ran a 14.7--seems a little sick to me? idk does anyone have any clue what could cause this? ITS KILLING ME thanks

 

Backfire through intake is usually caused by poor ignition timing. Since you can't time an LT1, I would look into your valves. Check the valve lash.

I had a bent valve and it backfired really bad through the intake but it wasn't drivable.

Do you have cats?

 

cat is gutted car drives fine under normal conditions its ONLY when i pull a hill in a higher gear and put it to the floor

 

That can be so many things, fuel, trans, clutch, ignition, dirty or clogged injectors, low compression not really enough info but im guessing you dont have any check engine light on or you would run codes sometimes they come and go letting you know periodically that something is wrong.

 

i know its not an ignition problem or dirty injectors and no check engine light

 

If this list of mods is all you have done to your car then your idle shouldnt be higher than 600 rpm stock is 550 rpm. So id be checking my iac, fuel would not be causing this either. To me if it were idling that high then it would seem that it would sound kind of rough which a car with yor mods should not. How much have you driven it since the rebuild after the wreck and has it ever worked properly since the rebuild.

 

ive driven it about 2000 miles its done this ever since i repaired the car it had a few vac leaks when i fixed it hoses etc. had popped off during the accident ,it has a new iac, it seems to run a little rough but its not real bad, another thing if im driving through town it seems to shake when im in a higher gear kinda like it doesnt have enough power to pull --btw thanks for the help guys

 

Hey man if it happens when you put it in higher gear when going up hill you might be putting it into the next gear too early which always causes a car to bog down like your describing. LEt it rev up a little before you pop it into the next gear and see what happens i done know how much youve driven stick shifts but thats what it sounds like to me and i and you both better hope thats what that is. Good luck man and always check all fluids after a major rebuild expecially after your through with the first outing of driving around.

 

ive driven a stick since i got my license there may not be a problem i just thought it was weird that it does it only up a hill when the pedal is in the floor

 

Sounds like a lean misfire. I would check fuel pressure,vacuum leaks,maf readings at idle,fuel trims at idle,cruise and slight load. Should not do it long enough to set a code. The high idle makes me think vacuum leak

 

vaccum leak is kinda wat i thought

 

Sounds like a coil wire.By the way,when you gutted the cat, did you get every particle out of that thing?Cause the remnants can get clogged in the muffler.Just a thought.My02.

 

it has a brand new coil and module and new plugwires ir are you talking about the actual wiring harness wires? and yes i got all the remanants out of the cat