So i got my short block from the junk yard it has good compression out of a wreaked fc. well i got evrything hooked up and the car start's but only run's good above 3.5k rpm's anything under that and the rev's turn to choppy irreradic and it backfires like a *****. I have magnacore 10mm plug wires that are new i have a rebuilt tps and as far as i can tell evrything is hooked up can someone help me out here i would very much appreciate it. thank's

 

Could be a crappy EGR valve.

 

You know i thought the same thing because before i installed the egr valve i cleaned it it was very dirty actually it was completely clogged. I read somewere here about a test you could do to see if it was bad like clamping the hose that goes to it to see if the car run's better but i tried that and the car died.

 

clogged main cat maybe?

 

I guess a clogged cat might cause a backfire, too much backpressure might be being created. Can you pop the exhaust off and have a look down the pipe?

 

Im using the same cat thats was on my old motor the one that blew the rear rotor. i had to drive the car about 5 miles back to my house and it was backfiring crazy because the rear rotor was dumping raw fuel into the exshaust soo that could blow out a cat right?

 

Raw fuel and pretty much anything isn't a good mix. Have you always had this cat on this car? If not, have you noticed a lack in get-up and go since putting it on?

 

check the timing

 

Any link's to a walkthrough?

 

swap a different TPS and see what that does. mine backfired alot also and a new TPS solved that. i thought mine was good, but it pretty much went out over a short period of time.its worth a try

 

check your pressure sensor egr valve and make sure the cas has good resistance between the terminals when you look at the connector with the clip up 2 on left and 2 on right top and bottom to cheack resistance also did you put any atf or mmo in the plug holes before firing it up maybe even try the water trick my just have debris in there(remember junk yard could have sat there for years)

 

Try swapping your primary injectors with your secondary injectors. Sounds like a stuck closed or partially clogged primary injector to me.

Secondary injectors come online just above 3500rpm, so if everything is fine above that. Your secondaries are relatively good. If everything below that sucks, your primary injectors may be stuck/clogged/super dirty/ etc.

Since NA's injectors are all the same size (460cc), you can easily swap all of them around to diagnose which one(s) is(are) bad.