I have a bad misfire on my 96 z25 and I thought it was my plug wires as was the problem in the past.. but the wires are in perfect condition. After the 355/cam/porting/injectors and other goodies rebuild on my lt1 I took it to a reputable local performance shop for the tune. They fixed the choppy idle and made it run alot smoother and told me i had a light misfire and to just bring it back after i got that taken care of.

Now my problem is it has a HORRIBLE misfire backfiring like popping pop corn and the plugs are saturated with gas. I have a brand new opti so I don't know where the problem is?? I cant take it to the local performance because they are so busy and hard to get a hold of.

I also just replaced the ICM and I still have the crazy misfire

Any help would be greatly appreciated. Some people told me maybe its my MAF sensor? Some said the 30lb injectors are too big.. but it ran awesome with a light misfire right out of the shop.. it just progressively got worse

 

could be injectors. ide say you should sent the computer of and have it professionaly tuned

 

30 lb injectors are fine, but you MUST have the PCM retuned for them as well as the other mods you did. http://pcmforless.com/
I've had brand new out of the box opti's be bad, so you might want to check that or for burned plug wires if you did headers too.

 

good advice

 

the computer was tuned very well might i add.. it was tuned buy the owner of a performance shop that mainly builds race cars.. after the tune.. the car ran AWESOME then a few days later misfire.. im 99% sure its not the computer

 

did u try replacing the coil?

 

just got done replacing the ignition coil.. man it was hot out there.. anyways i still have the massive misfire .. anyone else have a suggestion

 

i would check the maf. Are you throwing any codes?

 

im getting the codes checked out today around 6pm.. im going to see if i can borrow someones mafs and swap it to see if mine is bad.. i hope something simple comes on on the codes tonight

 

yeah you should have a better understanding what it is. post up when you get it scanned

 

P1810
TFP Valve Position switch circuit malfunction
P1371
Low resolution too few pulses

These are the main codes that came up.. and i dont know what they mean

 

My DTC list does not contain those numbers.

 

we used the same one as autozone uses.. does anyone know what either of these codes mean and how to fix the problem??

 

Sounds to me like it might be the opti dowel is either in the wrong place or like what probably happened with mine is that the gears in the timing cover that the opti pin goes into is chewed up and throwing the timing off. My Lt1 is in the shop right now with a similar issue.

 

so you think i need to replace the opti?? there is a brand new one on there

 

Have you checked the opti harness for corrosion? You might want to check the PCM pins for corrosion also. But the low resolution pulse code has to do with the opit. It is looking for low and high resolution pulses. It is sees not enough of one or the other, it will throw a code.

 

umm well ur buyin parts for a z28. if ya get them for a z25 ya might have better luck! lmao sorry couldnt help it. Now just because the opti is new doesnt mean it will work. There is a thing called defective parts. Also are you sure everything is pluged in right? and your connectors are all good and not burt up or anything like that?

 

all the plugs and connectors are plugged in clean

 

how old are your 02 sensors? low res pulse is the opti I thought, someone correct me if I'm wrong. edit...I understand it's new but like someone posted it could be that it's not set correctly...unless it was working fine for awhile prior the backfiring. Also check under your hood at night, look for lightning, could be a wire resting on a header. Happened to me, replaced a good opti for a new one and turned out to be a stupid new wire on the stupid #5 primary and backfiring galore.

 

How old is your fuel pressure regulator? I had a diaphragm fail on mine and it was pulling raw gas into the intake manifold at idle when the vacuum was pulling. Then my plugs would get fouled out with gas and made it run terrible.