just finnished swap to 350 tpi 2 months ago and can't get to run without bad backfires. it is an 86 tpi converted to speed density. tryed running before I converted it, had mas air flow hooked up and had it idle with back fires and could not rev. swaped computers and insalled a new map sensor. would back fire at idle and a lot when you reved and let off even when you hold it at a certen rpm. have try adjustin fuel pesure from 32-55psi nothing seemed to help also haved timing everywere from 30 advansed to 15 retard. nothing helps checked valve adj is one half of a turn after zero lash. checked compresion is good on all cylinders. unplug the timing conedtor and almost idles and dosent backfire with like 15 degres advanced timming but wont rev when yah plug the conector in it backfires all the time but will rev. the computer is a 1227730 with a custom bernt chip flashes code twelve and sometimes the knock sensor code because I didn't hock it up yet. the chip eliminats pass and all emisions. If there are any other guestions I'll anser them as soon as I can please help I'm out of ideas. also I have checked the fireing order like 20 times and the rotor position.

 

When you set the timing, did you unplug the black and tan wire????

 

Yup, backfire's going to be timing related unless you put your cam in funky

 

yes I unplug the set timming conector. me and another tech were just talking and I think I'm going to try runnig a seperet ground to the distributer. because the intke is powdercoated and not sure if it is getting a good ground or not will let yah know what happens

 

well the ground ides didn't work. also when I had the valve covers off and adjusted the valves static all the one sapposed to be closed on #1 were and the same on 6. so I'm pretty sure the cam is in right I also know I checked it like 15 times before I put the cover on when I asembled it. but still it is a possibility just one I don't want to go after unless the is no other option (oil pan sucks to get off). the only other thing I can think of trying is another coil I'm trying to find one laying around and if that dosen't I think I'm going to try a whole distributer other than that I'm stumped. it will be at least untill tomarow night till I can try any of this so if there are any other Ideas I would apreciate them tanks

 

Since you say it idles and whatnot with the bypass connector unplugged, that makes me think it's ESC related. On the SD computers, that's located on the memcal. Buy or borrow a different memcal and see if that helps.

But on the other hand you said you had the same problem with your MAF computer. Kind of a reach to think the ESC module would be the problem in both cases.

This leads me to think it's more of a mechanical issue, either the dist., or the cam. Good luck, I hope you find out the problem. Oh, and so Ozzy doesn't get upset, come back and give an update when you solve it..

Did you change the knock sensor when you converted? The SD computer uses a different resistance knock sensor.

 

well the ecm and the memcal are borowed from a hot rod that runs with this setup so that seems to be out. no I didn't change the knock sensor yet I have it though. I'm pretty sure this wouldn't stop it from running just might let it ping a little. I'll post a fix if I ever figure it out I've been trying for months now.

 

The knock sensor may be the entire problem. The ECM uses its signal to retard timing to reduce "pinging". May be advancing to much causing the backfire without having proper signal from sensor.

 

well I tryed another coil today still the same. I thought the ecm retarded timing if it got a signal from the knock sensor so if it dosent have the signal then it would leave it alone. I'll try hooking it up this satterday as well as another distributer. cause I couldn't get ahold of one today. I'm pretty much out of any ideas so I'll try pretty much anything at this point tiered of working on it want to drive it.

 

Did you try pumping the pedal, wiggling the shifter and adjusting the fuel pressure to super high levels