well i got my tune yesterday and i just installed it and made sure that the car started and that was it i will drive it tonight and find out if that will fix the problem prolly not but i nedded the tune any way. form PCMforless

 

We put an AFPR on the car tonight and didn't help at all. We set it to 55psi and didn't make a difference, as he mentioned in his previous post he also got a tune for it. I asked him tonight if he has changed his fuel filter and he said no. Maybe the damn thing's clogged up. I'm running out of idea's, hell I think I am out

 

An AFPR wont do jack for more than a couple hours. After that the computer will just learn the new fuel pressure and adjust the injector pulse accordingly.

Try unplugging the MAF, and leaving it unplugged and see how the car runs in speed density mode. I've had a couple friends with f-bodies with similar problems, and its usually a bad MAF. You can unplug it, or swap it with a buddy's maf temporarily.

 

I have unplugged the MAF, it didn't run any difference. It still cuts out and pops out the exhaust.

 

well the car is still not running right. it still cuts out really bad on hard acceleration, mainly above 4000-4500. this is what we have fixed/checked so far,

timing marks
different injectors
AFPR
corrected the install height
checked firing order, like 23 times
adjusted rockers
installed new fuel pump, the car ran better for two days, then started running bad again, at the same time as the fuel pump install, we milled some material off the rocker arms because the S/A part of the rockers were hitting the valve retainer and the roller wasn't hitting the valve
tune
disconnected MAF
different coil/module
drove with a scanner hooked up, I didn't see anything out of the ordinary, timing was fine untill it started missing/backfiring, then it pulled timing out.


could a lifter be collapising under load? the more load the car is under the worse it is.

Any ideas. we have almost literally tried everything.

 

ttt

 

poppiong and backfiring under load is almost certainly an ignition problem.

When your spark plug doesnt fire, unburned fuel makes it into the hot exhaust and detonates, causing backfire. Im assuming you have new plugs and wires. Im not sure if there is a quick way to test the opti, or even to test for spark at high rpm. eg. at 4800 rpm, you should get 4800/8 sparks per second on each plug, i have no idea how you would count that.

 

You dont have a tear in the intake elbow do you? Maf in backwards *seriously...Ive seen it done a few times, to guys who know 10000x more than me*, still sounds like something is unplugged somewhere. You dont have any plug wires touching/arcing?

Good luck..sounds like a big PITA! Hope you figure it out.

 

we swapped the opti out also with a known good unit, did the same thing.

 

i hate to bring back this old thread again but, i have since replaced the intank pump with a walbro pump, and a AFPR and still no luck. i happen to run into a local guy in e-ville by the name of Van and we put it on a sun machine and dropped each cylender and all are firing. while it was under a load certain cylenders would not fire. for exampple the number one fuel fouled out. so we replaced it with a new plug and it did it a gain. so fuel pressure was way too high (52lbs with vac line off) so we bumped it down to 42-45(with line off). he suggested that i change my plugs and use the AC delco 44LTS's and to gap them at .035 and i did and i just came back from driving it and it did the hesitation up stairs again.

 

Ok, check this on your car. Turn off the lights in the garage and look for sparking. If thier is change it. Most likely I have seen the coil arcing out. Also if that isnt the proplem dissconnect the vacumn line to the egr and drive it. If it goes away you need a EGR. Let me know. Thier is only one way to put a 95 and up opti on. All the other ways it wont fit, but double check your dowel pin. If its in to far you can force it in the other 2 slots on the opti, But you should be able to tell if its on wrong. They usually slide right on if lines up right.

 

His EGR is deleted, and its a 94 car and has had 2 different opits on it, his and the one from my 93. Everyone that has worked on this car is at a loss. He has tried so many things and nothing seems to help. Good luck Mike you'll get it straightened out eventually.

Dan

 

Maybe i missed it somewhere in the thread but has the origional poster had his PCM tuned for that cam. I love the cam, 4 different builds, all needed tuned and bigger injectors to work well for me.

 

thanks dan for up dating everyone. yes i have had a pcm for less tune andi have also tuned it with me and a friend here localy who have a 95 t/a that runs 7.80's and tunes his himself. so he knows what to look for when tuning. i do have the walbro pump and i have change injectors just replaced stock one with some that were functional. same problem.

 

I still say change the oil sending unit as my 89 iroc did the very same thing at higher rpm`s gauge read funny and i changed it poof problem fixed no more miss. I would say it is worth a try as much time as you have it in so far. Mike.......