89 350 tpi swap into 91 rs 5 speed ran great for one month then it just started to backfire on highway.replaced maf didnt change replaced tps and properly adjusted it no luck.replaced ecm no luck need help any ideas would help. this car is drivin me crazy and costing alot.thank you

 

I've been thru this a little bit. Sucks you went right for the expensive MAF. What maf did you buy? Reman'ed one from autozone are garbage from what I've read. The only good ones seem to be the $400 Bosch MAFs. Hopefully you kept your old maf. Did you replace the fuel pump and MAF burnoff Relays? I had some problems and once I replaced those, it ran better and the good news is that all 3 relays are about $30 combined. Located at the driver side firewall at the corner. What about the cap and rotor? Have they been replaced recently?

Are there any SES lights, any codes? I know it sucks, but you need to be systematic at this point. And if you have access to a scanner, that would be the best.

 

Is it throwing the ses light?

 

tried 2 bosch mafs neither fixed my problem cap and rotor and distributor and module all new new ecu nothing changed.this car makes no sense all the relays are good i think ive tried everything fuel pump new and the regulater works fuel pressure is constant it has a hesitation on throttle until about 2500 rpm ....no ses light

 

had this same problem... was the distributor for me.

 

have you checked for vacuum leaks? Is it hunting of surging. FYI, typically surging occurs when the car is in motion.