idle rpm sounds right on. no tac so i cant tell exactly. I will take a look at the plugs in the morning and post a pic of one to have a look at. there is an exaust leak almost all the way back where part of the pipe has broken free of what looks like a glass pack but its way down the line past the o2 sensor.
As for the stator I wasent sure if that was the issue and i am no longer getting a code 14. i'll have to keep checking.
as far as koer code 77 Im not sure how to get the rpm to the desired level ive tried several times to wot test but i dont want to risk blowing the motor. I ordered the book today as well hoping it will give me a good description on how to do a wot koer test.

 

Well I think I may have found a soultion. took a look at the plugs and being brand new they looked a little dry and heated.

Was talking to a buddy at the store and he said the truck is bad about upper intake gaskets. After hearing that it all started to fall in to place. only does it when warm, its getting worse over time, no engine code about a sensor other then 41 for running lean. gas mileage getting bad and all the testing for fuel and vacuum.

so i spent the $8 on the gasket set and found a missing bolt on the opposite side of the intake under the opening where the air hose connects. all the weight of the intake is resting on the small bolts holding the upper together.

Anyone else think this sound reasonable as well? if not o well $8 and a day of fun pulling the intake off hehe. I do actually like it lol.

 

well i just finished replacing the intake manifold gasket and driving it to the store. Same issue. spit and sputter and code 41. I did disconnect the batt for 5 min and the code was current koer.

i did find a replacement intake support bolt and its in there now.

any new suggestions?

 

Time to go back and revisit that PIP error you had before. I have seen several cases where the PIP was bad, but triggered no code. I had one that exhibited that problem.

Does the misfiring happen all the time? only when cold? or warm? Erratic timing can cause all kinds of drivability issues such as lean or rich as well as misfiring/chugging.

I am leery of the break in the exhaust near the O2 sensor you mentioned. If there are any leaks ahead of the O2 will trigger a code. Depending on how far downstream, it can also affect it.

 

yeah after i got the intake done the truck started a new issue. its in perfect timing that it misses seems like one cylinder is not firing but then i take a metal bar and tap the front 2 injectors and it goes back to how it was.

as for the exhaust the leak is all the way back by the muffler. about 4-5 feet away from the o2 sensor.

still possibly the pip huh?

 

If the leak is 3'4 feet away, there should be no effect on the O2.

This new development is interesting. If the injector(s) is not firing that could explain the lean code.

 

yeah i did some more testing and listening while driving.

going down the road it will sputter as normal and now sometimes the front 2 injectors seem to lock up and not put gas in and the sputter stops but i have no power and the motor shakes like crazy.

then i tap the injectors and it runs with the sputter but has power and doesn't shake.

Think im gonna get 4 more injectors as the #4 and 5 have been replaced recently as they are shiny like new.

expensive but from what i see they are a problem for sure now and the pip may be a problem to deal with as well. Will update when i have this done.

 

long week.

So i replaced the distributor as oreillys had one for $80 lifetime warenty that came with the module. I also replaced the rear 2 injectors as well as the front 2 now only the middle 2 are left but again they look new or recently replaced.

after all the goos hunting it still does the same thing. once warmed up it sputters. Think im going to have the timing checked out just to make sure its not that.

any more help would be appreciated. Thanks guys.

 

I think I'm going to try to take a video of the truck running and going down the highway doing the sputter I'm talking about. it may be hard to hear but ill try it and post a video here.

Its all nasty and raining today and the wife took the truck to work so I must wait to do this.

 

I may have resolved the issue. did too much more reading and some people said to unplug the map sensor.
I unplugged it and the truck ran without a sputter after being warmed up. It had no power during take off but it did not sputter.

Are map sensors often an issue on the 1990 model?

 

Just in case anyone is still watching here I have resolved the issue with help from the forums.

Apparently there is a big issue with the egr system where it just puts too much back in the intake.

After simply un-plunging my egr valve it fixed the issue completely. Now I"m off to build a restrictive plate or do the body washer thing as mentioned in the thread about this issue.

Thanks for all your help guys we got it fixed.

 

Good to hear!

I too hopefully found my wild goose chase too. For the past year my 89 F250 would not start, no pumps, spark or codes sent out, wiggle the main harness and will start up(still no codes set). This was intermittant and once the harness was moved problem is gone till next start up days or weeks later. Just with in the past month it started to shut down while driving, the tach drops to 0 and engine coasts down and stalls. Well last night I went to the store and got down the road, it stalled and this time no matter what was wiggled, no start! Finaly it hard faulted to be able to track it down! I finaly found the main ECU relay is the culpret! It has bad contects and that is hopefully the problem. Now to dive into the parts pile and get another relay.

 

Glad to see you got it resolved.