Originally Posted by Richardswilliams1

Have seen tremendous amount of threads about High idle issues with theese trucks. Especially high idle on cold start. Im old school 73 years old and here is my thoughts that might help someone. Im not a certified tech but have been playing with theese damn trucks a long time. First of all, 87 and up f150s are ALL way over engineered. Mine now is a 1991 f150 4.9 eng. When I first got it it idled high all the time. #1 problem like everyone says is fix vacum leaks. After replacing vac. hoses only High idled at cold start for about 4 sec then setlled down. Anything over 2k idle anytime is too high i dont care what anybody says. I replaced manifold air temp sensor, coolant temp. sensor, map sensor and stupid IAC. This brought cold start idle down from almost 3k to 2600. Still way too high. Didnt replace egr,egr solenoid or tps as they appeared to be working. Dont have scan tool or all that crap. The 2600 at cold idle only lasted for 2 seconds at this point. Much improve but still not good for engine. Here are the last 2 tips that helped A LOT ! Saw a video about starting the truck in nuetral instead of park to help with this. I was sceptical but it did help ! Started in neutral it goes to 2100 then settles down. The last thing I did to help is turn the key on, put in nuetral and then PUMP THE GAS ONE TIME before starting. Doing this the truck starts at 1800 then settles down. All the afore mentioned is in cold weather 40 to 60 F. Above that the truck starts at about 1600 then settles down. I cant for the life of me figure out why pumping the gas one time lowers start rpms by 300 but it does. I know there is a fuel press. regulator but dont know how Obd1 system can know this. The only reason I tried this was because I remebered that way you were to suppose to start carbureted vehicles. Maybe someone can shed light on it. Im convinced designers are told not to make anything that will last more than 5years. Thats why they quit making 7.3 turbo diesels, 300 CI inline 6s, Slant 6 Chrysler engines ! Poor folks like us have to reverse engineer stuff to mak it last.

Originally Posted by My4Fordtrucks

Way over engineered? My ‘89 has a manual transmission, manual transfer case, manual hubs and no power door locks or windows.

You repaired vacuum leaks and the idle came down the same way it would on a carbureted engine. I agree that a constant idle or 2K is too high. It is also not normal for it to be that high. It should be 700-800 rpms after the couple second 2Kish fast idle. Then you threw your wallet at it hoping it would be different/better because you do not own a paper clip, DVOM or test light to check for fault codes?


How is 2600 for two seconds not good for the engine? What is the fast idle speed on your carbureted engine when you set the choke? Pushing on and releasing the gas pedal one time does nothing unless there is a problem with the TPS. The fuel pressure regulator is mechanical without a sensor so you’re correct that the computer does not “know” it is there. It does however know when something is wrong with the pressure because it cannot properly adjust the fuel injectors to provide the correct amount of fuel.

You can thank the government for some of that. The same reason the Jeep 4.0L was killed off- it could not meet the ever stricter emissions standards.