I saw a while back that someone had a sorta similar issue, but was a 5spd car and not an AOD. I've posted this on my local fox club page with no for certain cures
So here's a rundown on what's been done to try to clear a low end stumbling/misfire along with excessive gas fumes at idle, and to add to it, during cruising 70 to 80mph on interstate there is an occasional pop/cough in the exh system, all of this occurs after warmed to operating temperature and in above 35 degree weather and tends to get worse the warmer the eng and weather temp get....... TPS changed, O2 sensors changed, fuel and a/c – WOT relays switched, plugs changed, IAC cleaned, coolant temp sensor changed, IAT sensor changed, distributor with new TFI module replaced (stock distributor), cap/rotor replaced, new fuel pump with new sock filter, new inline fuel filter, MAF meter cleaned , BAP sensor tested. EGR system has been cut and capped off, new coil. A cylinder balance test preformed with no faults, compression check done (all cyls were in the 90’s with about 6 psi difference). A water test(squirting water on the header tube at head) indicated #2 is where the problem lies. All header tubes immediately boiled off/evaporated the water, #2 took at least twice as long. Both times, when plugs were replaced and when the compression check was done, the plugs were burning good and were all consistent with the electrode/ceramic color. Fuel pressure checked (40 psi) No codes show during retrieval except pass codes most of the time, only exception is code 96 Fuel pump circuit, but disappears. it does not always show after the misfires
Specs for the car: a 92 GT 5.0 with an AOD trans and nearly 300k miles, NO MODS all original except for no cats and has Flowmasters
So here's a rundown on what's been done to try to clear a low end stumbling/misfire along with excessive gas fumes at idle, and to add to it, during cruising 70 to 80mph on interstate there is an occasional pop/cough in the exh system, all of this occurs after warmed to operating temperature and in above 35 degree weather and tends to get worse the warmer the eng and weather temp get....... TPS changed, O2 sensors changed, fuel and a/c – WOT relays switched, plugs changed, IAC cleaned, coolant temp sensor changed, IAT sensor changed, distributor with new TFI module replaced (stock distributor), cap/rotor replaced, new fuel pump with new sock filter, new inline fuel filter, MAF meter cleaned , BAP sensor tested. EGR system has been cut and capped off, new coil. A cylinder balance test preformed with no faults, compression check done (all cyls were in the 90’s with about 6 psi difference). A water test(squirting water on the header tube at head) indicated #2 is where the problem lies. All header tubes immediately boiled off/evaporated the water, #2 took at least twice as long. Both times, when plugs were replaced and when the compression check was done, the plugs were burning good and were all consistent with the electrode/ceramic color. Fuel pressure checked (40 psi) No codes show during retrieval except pass codes most of the time, only exception is code 96 Fuel pump circuit, but disappears. it does not always show after the misfires
Specs for the car: a 92 GT 5.0 with an AOD trans and nearly 300k miles, NO MODS all original except for no cats and has Flowmasters