I have a 1991 4x4 with 5.8l. The other day I blew the small hose that feeds coolant to the throttle body. No overheating, just messy.
I replaced said hose and flushed and filled with fresh coolant. All was well until truck was warmed up on shakedown run when the idle started surging and stumbling.
Looked for vacuum leak and eventually replaced thermostat thinking system was confused by a low temp reading[my truck has run for years at the bottom of "normal" on temp gauge, but seemed slightly lower than usual].
Searched the forum and cleaned the idle air control and switched the map sensor from my buddies truck with no change.
As mentioned the leak was messy but has since dried for two days,could the leak have damaged another sensor in the throttle body area? BTW my check engine light has been on intermittently for 150k miles and I pulled the dist cap looking for moisture or arcing.
Seems to idle fine when cold and run and pull well when warm but has stumbled at stoplight bad enough to die once.

 

Have you pulled the codes to see what the computer has to say? See what codes you get, and that will make it a lot easier to narrow down your problem.

 

no code reader at my house,my buddy may be able to help me out tomorrow. Perhaps stubbornly, I am stuck on the idea that it is related to the drenching the area got during my leak and repair.

 

BTW where does the code reader attach on this vehicle?

 

No code reader is necessary. This will tell you how to retrieve the codes:
https://www.f150forum.com/f10/how-retrieve-trouble-codes-obdi-10907/

 

Since my last post I discovered some bare wires touching at the bottom of the throttle body. I believe they are on the throttle position sensor. I removed the throttle body and insulated the wires and the idle has smoothed out though it is a bit faster than before. I did clean the throttle body contrary to the sticker on it that says not to[couldn't help myself]
Before this exercise I tried to read codes as described from check engine light. I took the instructions literally and left out the volt meter but still jumped to positive battery. Got no KOEO codes at all.
I then went on to running codes by disconnecting jumper and revving for two minutes. As soon as I started engine the check engine light began flashing and it then occurred to me that leaving out the volt meter also included leaving out the pos jumper.
Using that approach got me a 99,a81 and a 22 [ afriend suggested the codes are all at least two digits,distinguishing between a two or a three second delay is difficult while writing down codes]
The running test was less clear, I was looking for four flashes indicating 8 cylinders and never got them.
Finally, could I have reinstalled the throttle position sensor incorrectly resulting in my faster idle? It did require placing the sensor slightly offset and twisting slightly, engaging the "tooth" and lining up the screw holes.
Thanks for your time,please let me know if those codes are meaningful or give me a little more guidance on reading and recording the codes Bill

 

22 is the MAP sensor (up under the passenger side near the firewall - has a connector and a vacuum line on it). Check the vacuum for that sensor.

81 is the air management circuit 2 failure - I don't have a clue what that means...

99 is the electronic pressure control circuit failure (this is for the E4OD tranny) - if you don't have that tranny it's probably an incorrect code.

I'd disconnect the negative battery lead, work on the MAP connections, and then reconnect the battery. Check codes again, and maybe the 81 and 99 won't be there (could be related to something from the previous issues). If they come back, hopefully someone here can help decode the codes.

It helps on the TP sensor to mark it before you remove it, so putting it back in the right place is easier. It has a slight rotational adjustment, which will affect idle (I think).

 

The reason you shouldn't clean the throttle body is because it has a coating on it that is destroyed by cleaners. You should have marked the TPS before removal so that you could get it on in the same position. While the 4.9 TPS isn't adjustable, all others are, so the idle problem may be because of this. If you don't want to go through the trouble of hooking up voltmeters and checking voltages, maybe you can set it by ear by loosening the TPS and twisting it until the correct idle speed is reached.
Code 22= MAP out of range. Probably a vacuum problem.
Code 81= air management 2 circuit failure. I believe this is part of the smog system, actually a controller for the smog pump. This may also be a vacuum problem, the valves for the smog pump airflow control are vacuum operated. There may also be a solenoid problem, the solenoids allow the vacuum when needed. Check the fuses and connections to the solenoids.
Code 99= electronic pressure control circuit control failure (E4OD). Once again check fuses and wiring to the transmission. This is assuming you have the E4OD. I also have a listing for this code as idle not learned, but is more likely the transmission code.

 

Thanks for your replies
code 22 map sensor may have resulted from quick and dirty test of pulling vac line and plug individually while idling to gauge effect,I have also swapped with a presumably working map on a buddies truck with no effect.
code 81 my truck has no air pump as I discovered when the serpentine belt called out by napa was too long,the diagram under the hood does show it though. I would be surprised if it was removed in the first 80k miles before I owned it [current odometer just north of 260k]

code 99 I do have the E40D,new filter and fluid about 30k ago. No symptoms except an occasional hard shift, leading me to ujoints from another post. Amazingly, have same ujoints since I have owned [180k]. The "idle not learned" idea is intriguing as I have only driven perhaps 5 miles since disconnecting battery to clear codes. I have seen posts talking about the CPU? " learning". Perhaps I should be patient with the fast idle?

TPS does not seem to be adjustable. Screws do not have slot to allow twisting. When I reinstalled it the "tooth" on TB interfered with the "cogs" on the TPS preventing a straight drop of the TPS over the screw holes. I turned it slightly CCW [ upside down,TB was off for access] until it dropped flush to TB, then slightly CW to line up screw holes.
I will pull codes again in morning, can anyone confirm that codes are all 2 or 3 digit? Any clue why running codes aren't working including no 4 flash to indicate 8 cylinder? Am I correct to assume that with check engine light no jumper to 12V is necessary
Thanks again for your time and expertise Bill

 

ujoints look and feel good, will drive today and pay attention to hard shifting

new codes
KOEO = 111
Continuos code = 332
running codes do not seem to be present, I did get the four flashes indicating 8 cyl, then pushed brake pedal. No further flashes Bill