I posted about this before but I wasnt sure on my problem, now I got it nailed down.

I rebuilt the engine with the mods below and now occasionally at 1900-2000 rpm - no other rpm's - the engine backfires out of the tbi. Im sure the distributor is on, we double checked that, and we double checked all the rockers (no chatter then 3/4ths turn), so I think my valve train is OK.

It was really bad and I upped the fuel puressure and backed off the timing from 10 to 6 advance, which helped out considerably. I raised it to 8 and I was flooding when I tried to crank it over, but I think that was because my throttle linkage was holding the tbi open I'd say maybe 4% (dont know exact number) when my foot wasnt on the throttle. I fixed that, but I didnt get a chance to add timing before I left for school.

My fuel pressure is near the top of the pod, maybe 1/8 to a 1/16" from the top. Stock injectors, sorry no fuel pressure gague. If I pull down the fuel pressure at all the car wont pull at all, and it struggles to get past 70 mph bad.

Should I increase my fuel pressure some more or add timing, pull timing, or what? I cant afford the chip burning stuff now so all I can really play with is timing/fuel pressure.

Thanks if you can help me! I want to run it friday, but not with the bad backfire.

 

Sounds like your timing is off. Try advancing the timing, see if that helps, it did for me when I kept on running into that problem with the stock eprom. Then if that doesn't work, return the dissy to the original place and crank the fuel pessure up, see if that makes any bit of a difference. It's all trial and error unless you get a hold of winaldl or get your hands dirty and do plug cuts.

 

I got winaldl, but havnt had any time to run it with the car. I'll definatlly log the data when I go down the 1/4th.

Thanks for the help man