freebird_775

just dropped a centerforce clutch in my 91 300 miles ago. so i decided to do a little muddin. (of course i had to show up my buddy and his ford250, which i did.) but sucked in some water in the process. i've done this before nothing new, but when i went to restart the truck it after fired really bad and split the muffler wide open it idled rough and the check engine light blinked and idled high i guessing because its wet. but 2 weeks later im having idle problems. when i stop at a red light it kicks into high idle (about 2500 rpm) but the truck is at normal temp. and then 15 seconds later it drops down to idle but runs rough and 3 or 4 seconds later kicks back up to 2500.

the motor is dry, there's no mud or water in the intake, no check engine lights, new muffler, air filter is alright


(3 weeks before i went muddin the truck was bogging out really bad where i could have it to the floor in first and barley have enough power to to get to 15mph until it got to about 3500 rpm then it would take off but this problem went away before i went muddin and hasn't bogged out ever since)

whats going on???

abecedarian

Below the throttle body, and towards the radiator, is the PAIR resonator- looks like a big toilet bowl float and has a hose coming out of the top of it which runs behind the radiator to the air filter housing. Pull the hose off the top of the resonator and PLUG the resonator so that air cannot get in, and also plug the hose to the air filter. See how it runs. If the swinging idle goes away, the after-fire probably blew out the PAIR reed valve (blocking the resonator keeps the system from sucking air in). The reed valve is below the intake manifold and to the rear of the fuel filter on the intake side of the engine block, and if plugging the resonator fixes it, it's allowing air in to the exhaust and is mucking with the air/fuel ratio readings to the O2.
If that don't help... maybe ought to check the converter and see if it was damaged during the ordeal- excessive backpressure can muck with the idle and air/fuel mix too.

Also, try cleaning the throttle linkages so make sure that they're not sticking, the dashpot isn't causing isssues... maybe when it's idling high go under the hood and see if you can turn the throttle closed tighter and make the idle more normal... things like that.

freebird_775

ok i did the resonator check and that wasn't it. i cleaned out the dashpot because it was dirty and it got better but still doing it.