nameiztaken
Member
- Joined
- June 9, 2021
- Messages
- 38
- Reaction score
- 14
- City, State
- California
- Year, Model & Trim Level
- 1991 EXPLORER XL
Making a dedicated thread for this, hopefully someone here has some tips on possible causes or things to check.
Getting some mild to heavy pinging on 87 octane when putting the vehicle under load (merging on highway, grades, etc). Its a 1991 4.0 with the 5spd. Also getting a somewhat rough idle, but nothing serious.
I think the IAC may be broken - as unplugging it changes nothing. I cleaned it and had no improvement other than raising my idle rpm from ~800 to ~950. It does not appear to move when I turn they key on with the engine off. One fuel injector is ticking louder than others (checked with long socket extension)
Some of the stuff I’ve tried:
Replaced lower/upper intake manifold gaskets
Searched for vacuum leaks, couldn’t find any. Unplugged individual vac lines at tree and plugged the tree, no change
Replaced fuel filter & checked pressures, ~29-39psi
Replaced spark plugs and wires with autolite single platinums
Replaced coil pack
Replaced pcv valve
Cleaned maf (3x)
Cleaned throttle body and IAC
Cleaned intake air temp sensor (2x)
Used seafoam through brake booster line
Used techron in the gas (2x)
Not much difference after all of those repairs.
Getting some mild to heavy pinging on 87 octane when putting the vehicle under load (merging on highway, grades, etc). Its a 1991 4.0 with the 5spd. Also getting a somewhat rough idle, but nothing serious.
I think the IAC may be broken - as unplugging it changes nothing. I cleaned it and had no improvement other than raising my idle rpm from ~800 to ~950. It does not appear to move when I turn they key on with the engine off. One fuel injector is ticking louder than others (checked with long socket extension)
Some of the stuff I’ve tried:
Replaced lower/upper intake manifold gaskets
Searched for vacuum leaks, couldn’t find any. Unplugged individual vac lines at tree and plugged the tree, no change
Replaced fuel filter & checked pressures, ~29-39psi
Replaced spark plugs and wires with autolite single platinums
Replaced coil pack
Replaced pcv valve
Cleaned maf (3x)
Cleaned throttle body and IAC
Cleaned intake air temp sensor (2x)
Used seafoam through brake booster line
Used techron in the gas (2x)
Not much difference after all of those repairs.