im driving down the highway and my truck starts to backfire and spudder. ive got 1/2 tank of gas. changed thefuel filter 3 weeks ago. cap/rotor are about 6 months old, but i put on a higher voltage coil 3 weeks ago as well. the truck only backfires when you push the throttle. i bought a new cap and rotor and put them on this morning, and it works fine. do i need to go ahead and swap out coils or is there something else wrong?

 

I know you just fixed the timing but check it again. In my painful experience, back firing has always been a timing related issue. Had that problem in my Conquest TSI, kept changing the plugs and that would fix it for a day or so then bad again. Ended up replacing the distributor and haveing to toy with timing to get it to quit that crap.

 

almost always a cheap cap gives ya trouble

 

i bought an Accel cap and rotor for about $40. today i took out the Accel coil and put in the stock one. it worked fine, so im thinking its a bad coil. ok, so i bring it back and get a new Accel coil. that one worked for about a minute and it started to backfire when i accelerated. now i have the stock one back in and it works fine. could this be a manufactuer(sp) defect and the whole batch gone bad?

 

i bet that accel coil isnt putting out enough for the engine.

 

but the first coil ran good for 2 weeks... its a high performance/voltage coil. same thing as MSD

 

That's strange... Maybe the Accel is too much for your factory ignition system. It may be overheating some of the ignition system components.... just my wild guess. You really don't need the Accel coil, it isn't going to help much at all. Atleast not without an entire Accel ignition system. That is Accel ignition module, wires, and whatever else.