1994 f 150 5.8 L engine , E4OD transmission ,2 wheel drive --- this truck drove fine till backing up on day and stalling the engine since then have an extremely rough idle/ stumble -- no vacuum leaks found ,, checked and replaced all the usual suspect modules except for the distributor and ignition module -- my question is ,,,, how much influence do transmission fault codes have on an engine at idle , and where else should we be looking to rectify this issue.

 

Transmission codes have no effect on idle quality. I would pull spark plug wires off the distributor one at a time at idle (using insulated pliers) to see which cylinder is not firing.

 

Sounds like a faulty distributor to me or maybe even some burnt or bad ignition wires.....A faulty coolant temp sensor CTS for the PCM to get a temp reading for referrence [not the temp sensor gauge for the dash] will cause it too........

Whats the mileage on your truck and when was the last time you did a timing chain , thrust plate and inspected the harmonic balancer for accuracy?

When was the last time you did a KOER cylinder balance test?

If it is the distributor that went bad theres a really logical reason behind it and that is most likely due to a worn timing chain coupled to too much cam walk as the start to all gremlin related problems eminate from this area..Ill explain better read on.....

Timing chains have a service life to them and must be changed according to Fords requirements and theres a strict reason behind it other than trying to leverage money from your wallet for seeemingly no reason as most of us are trained to not attempt to fix something that isnt entirely broken when you can use the time and money to buy and drink beer...I dont drink alcohol or smoke cigs either.....LOL.

Ford Motor Company states in their service manuals that every 100,000 miles the timing chain and thrust plate should be changed along with the waterpump , waterpump bolts and thermostat..o .It also says to inspect accuracy of the balancer and Serpentine belt and to replace if rubber seems cracked/deteriorated or doesnt conform to timing accuracy..

Stickshift vehicles and ones used for commercial style work trucks are required to do so 20,000 miles earlier than non worktruck use automatics too..

Back in the day Ford dealerships were always offering $350.00 timing chain replacement services on engines from 100,000 miles and above and were even putting out ads n commercials about it too...Now no-one really cares because it causes so many problems it causes people to give up and junk them which is what the govt prefers also some mechanics wont devulge this if they knew especially when theyre buddies with a Ford guy because there is always an opportunity for making side money while the ones looking to stop hemoraging money in this fashion and refuse to give up on their trucks while hoping & awaiting on a miracle fix end up here as a DIYer to save $$$ after replacing part after part only to acheive temporary satisfaction..Some here actually like a challenge thinking the mechanic is playing them while some are actual mechanics from a later time that cant figure the problem out seeings ALL DATA doesnt cover anything as Ford made it that way back then to keep their own techs employed and even get business from experienced mechanics too..,,,......LOL..

Ignoring the requested service of key items at certain mileage intervals youre just destroying your Ford trucks reliability and asking for the gremlin related problems to pop up and plague the vehicle as Fords timing system is calibrated in the pcm with limitations to detect and correct if needed when it doesnt conform and can correct the issue only so much and for so only long before it goes into thermal overload from trying to correct the timing when it goes in the ranges it cannot even understand so it relies on the programming on the chip to take over and take up the slack but it eventually causes the part to fail due to thermal overload........Most people cant drive their trucks for more than an hour straight before having to let it sit an hour.......Yet from zero miles until when the timing chain fully worn out it wasnt an issue nor were there issues.....

Most dont realize either that even though their trucks run alot stronger and peppier advancing the timing past 10* btdc this is a no-no as the pcm is trained to detect only 10" BTDC..Thats where tuners come in to do the task of getting more pep and power and that starts with a much larger fuelpump like a 255lph or even a 340lph pump then tweaking the fuel and timing tables...IMHO Ford should of made their distributors non-rotational by using a special lockdown that only locks down at one spot like on my Vortec 350...

Another fact that make the problem evident and more clearer to understand where the actual problems lie with our trucks is Kenne Bell the developer of the EEC ignition system thought he was shrewd at the time to achieve sequential fuel injection in a much more simplified also methodical way by making the distributor pull double duty as a camshaft and crankshaft positioning sensor instead of having a seperate crankshaft sensor like the Vortec 350 Chevies utilize which allows the engine to see the actual differences in wear between the crank n camshaft due to a worn out timing chain and correct the problem and keep them engines running way longer with zero running gremlins other than a lil lag at start-up when hot too as my 1999 Chevy suburban has 375,000 miles and never had a timing chain done yet you can hear the chain slapping the t-chain cover and has zero running gremlins,...;-not even a check engine light..........lol.




Once the lower distributor bushing wears out it causes the distributor shaft to ground out and the distributor shaft to short to ground or cause running issues or the TFI module or the Halls effect pickup to go into thermal overload which causes the problems you describe............................

One more question....Was the truck cold and just started or was it at running temps and driven around prior to the problem happening?

 

Say the computer stores a code for torque converter clutch failure or torque converter solenoid failure, or torque converter unlock failure(if there is such a thing), then absolutely will have an effect on idle while IN GEAR.

Your engine will stall when in gear if the torque converter is still locked-up, or idle low if partially locked-up.

Check for codes first. There has been a lot of posts lately with people throwing parts at the vehicle without proper diagnoses.

 

What is the level of your transmission fluid? Low or High or perfect?

 

I had a weird issue when my trans fluid got low while I was towing and the transmission also didnt have a brake light switch signal(aggressive lockup and other things to try and keep it from able to overheat I believe?) and It was loading down my engine quite a bit like I turned it off in neutral and I could almost NOT start the truck while moving in neutral, it was so hard for the starter to turn which made me think my trans isnt both unhooking torque converter normally but it may have been dragging. i stopped in a town 2 minutes later, put fluid in,scratched my head as i had no codes even during this(had tool with me) but i let it sit for a short while and it started fine and acted normal again.

Was weird

 

just to clarify my original post ,,, we had just reinstalled the engine with new timing chain , exhaust manifolds ,, egr tubing ,, etc. filled with coolant . warmed the truck up and took it for a drive ,, stopped to fill the tanks and proceeded home a round trip of about 10 kms ,,truck drove excellent ,,, went to back it into the garage ( garage has slight up slope ) and front wheels did not roll over floor edge and stalled the truck ,, it did blow some black smoke out of the exhaust on restart and since then the idle has been terrible and will stall going into gear. while checking the different modules found out the previous owner put a coolant temp sensor in the air temp sensor port on the intake changed that out for the proper sensor and now i am thinking to check to make sure he did not install a air temp sensor in the coolant temp position. but if you fellows have any other ideas please forward them .. we are ready to pull the injectors for a cleaning / replacement but will check ignition first. thanks fellas

 

In your scenario, the code is not causing the idle problem, the TC failure that the code is reporting is causing the problem. Maybe I am wrong, but I read his question as "does the computer make changes to the engine based on a code it has stored?"

 

Right, gotcha. That question would depend on the code that is stored.
If there are stored transmission codes, I think the only change the computer will make is possibly put it in limp mode.
If the ACT or ECT is out of range, then the computer will make changes based on other data.

Now, since we know , another possibility is that the Torque Converter was not seated all the way, and this can also cause the rough idle and stalling issues. Not a good situation if this is the case.

 

aww come on don't tell him insulated pliers that is no fun.