I have had a problem with the car back firing alot after hard acceleration.. After taking it for a diagnostic run with my mechanic we found out that when the car is backfireing the computer is completely shutting off for a like a second or two and then turning back on... I think it is a bad ground or positive wire somewhere but don't know where to start.. It only does this after hard acceleration and not every time but most of the time.. Where Should I start and or what should I do..... thanks,for any advice.. also my subframe connectors are rattling on the exhaust is there anything I can just put inbetween them that won't burn or start on fire.... I can't move either the exhaust or subframes in either way.. thanks,

 

What year is your car?

 

It is a 1995 z28.....

 

I had the same problems, as you. Hopefully I can save you the grief I went through. My tach would jump like, especially after gettin on it hard or a big pot hole. The tach made computer think it was at redline and would cut fuel off. So with that mechanic thought it was bad opti.

New opti and new waterpump later tach still has flopping around not as bad but still there.

Turns out that my groundstrap and my airconditioning hose behind the compressor had gotten togethaer. So i was out a 120.00 a/c line and ground strap, but that fixed my problems. I would look there first.

 

How did you determine this?

 

the computer is not a switch. sure it can have a bad connectin and lose imputs but it can't just shut off as a whole. it's suplied power and ground on several wires. any of these wires that do not make connection can cause problem but it will not "shut off" I guess we could use more info

 

Well I pulled the computer box out today and wiggled all the wires while the car was running and checked all the main grounds.. With no such luck.. what yousaid does make sense though.. I am just completely confused.. when we took the car on a diagnostic run all the sensors where reading accuratly and the graph was showing when we accelerated and let off and even shifted... then the car would back fire for about two to three seconds and the bar graph would just go blank and all the sensors would go to zero as if hte car wasn't even pluged into the diagnostic machine... Please help this problem is really pissin me off. thanks,

 

Check the PCM battery feed from the IP fuse panel, fuse 4 ,orange wire, for continuity and a possible intermittent open (break). Check it all the way from the fuse to the PCM. There is one connector under the right hand side of the dash behind the right hand kick panel. It has 4 cavities (pins). The PCM has several ground wires, some for redundancy, and are (2) tan/wht wires grounded on the left front of engine block just below the head on a stud for the coil mounting. And also 2 white wires spliced with some sensor wires in the main harness approx. 4cm from the main branch and PCM breakout. from the splice it goes to one wire, grounded to the RH side of the block just above the starter. The problem could be inside the PCM also. It could also be a DLC wiring problem. But for the PCM to lose memory it would have to lose the PCM batt feed. There are too many grounds for all to fail at once without other apparent problems too. Check them anyway.

 

FWIW I've seen this happen many times first hand with difrent cars. I'm not really sure why it does it though.

 

FWIW?