'92 Bronco xlt 4x4 5.8L e4od - just got done installing a gt40 351w from a 93 lightning, man its fun now! while the engine was out i replaced the tq conv. and gave the tranny a new filter and fluid change, and a qt of lucas tranny treatment. ran awesome for the first 1k mi or so but the tranny has developed a stumble that seems to be getting worse. from a dead stop it starts out fine in 1st, but when it shifts to 2nd it has a minor stumble (2-4 light jerks) and smooths out. this only happens under light/part throttle. under wot its fine. same issue happens in 3rd gear at about 35-40mph and in o/d at cruise speeds. going from very light throttle or light deceleration and giving it just a bit of throttle i fell a jerky stumble for just a second or two, then it smooths out. the more throttle i give it the less it does it. cruising at 65mph when i back off the throttle and reapply it does it about every time, and if i hold pedal just right i can make it happen for several seconds. i am very confident it's not an issue with the engine, it runs flawless, though the issue gives the impression of a miss. i'm prepared to have the e4od rebuilt, just hoping someone may have dealt with this issue before. thanks

 

Remove, clean, replace, then test IAC for proper function.
http://www.fordfuelinjection.com/?p=39

Then do Error code scans. May end up w/ a transmission code, or even more likely, TPS out of range.

https://www.f150forum.com/f10/how-re...es-obdi-10907/

 

thanks for the info. already been there. just replaced the iac and the tps is dialed in - .92v/idle 4.85v/wot. has a new speed sensor in the rear end as well. new air charge sensor, new water temp sensor (for ecu, not gauge) abs controller is suspect of giving this truck issues before, not replaced yet. at first i thought it was engine related, but i'm 90% sure its transmission.

also, it feels as though when i'm at about 65mph give or take when i let off on the gas it seems to decelerate a bit faster and i get a bit of a clunk in the tranny. feels like more drag. might be related?

i'll pull codes

 

only codes 552, 553 (thermactor air pump codes) and 565 (canister purge solenoid) came up. eliminated the thermactor setup with the new engine, and the canister purge is not connected at this time, but shouldn't cause this issue. only other code was 111, system pass

 

RABS doubtful w/o RABS/ brake light. .92/ Idle for the TPS is a hair on the low side for our trucks. Closer to .97 is preferred. Is your TPS adjustable or fixed?

 

sorry. i meant .982v on the tps. it has a summit 65mm mustang style tb with the fully adjustable tps mount

no matter what changes i make on the engine management system (idle,tps,timing) the problem with the tranny exists and is consistent.

 

Well at this point, may I suggest Seafoam Spray treatment to clean carbon deposits from the intake systems, intake valves, and combustion chambers of your engine. Also Lucas Injection system cleaner added to fuel.


http://www.seafoamsales.com/how-to-u...oam-spray.html

I know your thinkin "Dude it's the tranny!!!" Normally I'd suggest a can of Transtune w/ this type of disfunction but you've already serviced the unit. Don't normally push chemical this much but your not showing any mechanical/ sensor cause that's easily rectified.

Have you rechecked your Tranny fluid level again since servicing?

I'm aslo not a fan of eliminating engine components that play w/ the EEC.

Thinking disconnect the battery for at least 5 minutes to clear the Kept adaptive memory. Your problem "may" disappear temporarily while the ECC rebuilds the KAM. That information would be important.

 

the engine itself has less than 37k mi on it, and i had the intake off when i installed it and it looked pristine in the intake ports and head runners. the egr spacer and tb are brand new. can't say it's a good candidate for seafoam. i'll try disconnnecting the battery and see if the computer clears away this issue, even temporarily.

it really does feel like a missfire. i may try throwing a new distributor and tfi at it and see what happens. there really isn't much left after that

also. at idle in neutral if i reach out and rap the throttle wide open is does seem to have a very minor hesitation on it's first reaction to wot. i'd say around 1000-1500rpm, which is about the rpm the stumble happens at cruise speeds. almost feels like it takes a second to catch up to the rapid increase in throttle. kinda get that hollow sound thru the cold air intake

 

Back in the late 80's/early90's, there was a bulletin about plug wire routing, seemed the was some cross firing going on, cyls 6&7 I think. Your concern is all over the place, something to think about, expecially with the recent engine replacement. Offer no thought on the tranny, have no experience there.

 

What is your normal op temp Idle RPM?

Thinkin more air or fuel.

Also, you may want to check your fuel pressure after engine is shut off to see how fast you loose pressure. Implying a hanging injector.