91 L98 6 speed, mild cam, forged pistons, custom chip, and ported. Serpentine belt broke ran hot 260 for a minute or so. After replacing belt there was a miss in the engine and acceleration retarded and backfiring through the exhaust when down shifting. Found 3 bad plugs. Installed 8 new plugs FR5LS .gap 035, ran perfect for about 20 minutes. Thought problem was solved but after starting the next day it ran perfect for about 10 minute turned it off after restarting the miss and retard as mentioned above showed up. Rechecked plugs they were OK. Head gasket OK. Next day drove the car hard for 90 minutes ran perfect. Again thought it OK. The next day ran great for 5 minutes stop for fuel after restarting rough idle, missing and retard, and backfiring showed back up.
Any help greatly appreciated.

nysec

 

Could be the fuel injectors or filter. If it happened when you refilled your tank, it most likely has something to do with the fuel circuit. It may even be the pump itself.

 

I'll throw the ignition module into the mix. They don't like heat.

 

You can rule out fuel by running a FP guage and taping it to the windshield for a while. When it acts up see if your FP is goofy....if not then move on to ignition

 

Rechecked plugs and wires found one wire not connected properly to the plug. reconnected but no change. Did resistance test on injectors (cold) #6 @2.5, #2 @8.50 others around 16.50.
Should I just replace all the injectors see if that corrects the problem before looking for other causes?

Thanks

 

Yes replace them all, 2 injectors are failed and the rest are most likely not far behind...nobody likes doing the same job twice so do them all at once.

 

That would coause your problem allright

 

Hey thanks,

Best brand for replacement?
Just read Sam Lam's instructions on removal of injectors. Any other articles or recommendations before I do this for the first time?

 

There is a supporting member here that I haven't used (I'm not the injector type) but there have been many good comments about their expertise and advise.

FIC injectors I believe

A search should do the trick and you can PM them

 

Great recommendation. I have contacted them.

Thanks

 

Don't know if your search brought up Rich at Cruizin Performance but he's the guy you want.

 

Thanks for all the help. Jon at FIC was the first I called and he had the Bosch injectors ready to ship so I should have them today or tomorrow.

Will keep you posted on how it goes, again thanks for the help.

nysec

 

A big thank you to forum members for your help.

New Bosch III injectors installed. Problem solved, car never ran better.
It was a pleasure to deal with Jon at Fuel Injector Connection. He was very helpful and the service was great. I want hesitate to recommend him to anyone.