flooding, surging, backfiring

[drunyon]

I have a 91 2.3 ranger. When driving it, it alternates between full power, and roughly 80% power. Sometimes very rapidly. If I drive it hard, or leave it in gear and coast down a hill, it will sometimes backfire, and most of the time flood and stall. I'm actually assuming it's flooding because of the backfiring. Sit beside the road for 5 minutes and it restarts every time.

What's super weird, is that about 2 weeks ago, after having let it sit for a while, I decided to start it up. It ran flawlessly for about 500 miles, then out of no where, the problem is back.

Could this be a sticking injector? I've replaced the FPR.

 

[RonD]

Welcome to TRS

On a 1991 I would suspect the ICM(ignition control module) that runs the coil packs, 1994 and earlier used these for Spark, and they were a know issue as they aged.

ICM is on the front side of the lower intake, it can be tested at most auto parts stores.

Backfiring is more likely misfires being ignited in exhaust manifold by next firing cylinders hot exhaust.
A misfire sends the correct air:fuel mix unburned into the exhaust manifold where it is ignited by next firing cylinder exhaust

Sticking injector is possible for sure, but would expect steady misfire on that cylinder and unbalance air:fuel mix might backfire but more likely for it to just make Cat Converter run VERY hot.

FPR was good choice to change, that would be my first guess, ICM is second guess, lol.

 

[drunyon]

thanks for the response!

is the icm something that could get better, then worse again? that's what made me think it was more likely a mechanical issue.

i'm sure the backfiring is just a byproduct of an incredibly rich mixture making it into the exhaust.

 

[RonD]

Yes, ICM can work OK and then not work OK, heat can also effect them, runs better cold than after warmed up, but not always heat specific