need help with idle adjustment of a ford e-150 econoline van, 1990, fuel injected 308. The repair manual says there is no adjustment screw. Here is what has been done, a so called mechanic shop worked on it for a different problem, (that has been solved by me) they cleaned the intake manifold, when I got the van back it had a higher idle, the shop would not work on it anymore, ( i don't think they know what to do!!!) so I asked around and was told that the "by-pass valve" witch is mounted on the intake manifold, could be clogged, so I bought a new one, installed it and now the idle is even faster...it can get to 40 mph with out touching gas pedal. I have heard that the idle is set by turning the distributor. Is there any thing else or is it right to set it by the distributor?? Many thanks for any help

 

LOL @ 40mph without gas pedal. It sounds like you have a vacuum leak. I don't think the idle speed is adjustable on fuel injected vehicles, it's controlled by the computer. Take it to a better mechanic!

 

There is no idle speed adjustment on these EFI engines, it is controlled by the computer so you have a mechanical problem most likely. First thing to do is remove the intake tubes and look to see of the throttle plates are fully closing, disconnect the throttle cable to see if that makes any difference, a sticking cable isn't uncommon. There is a throttle plate stop screw on the side of the TB but it's just there to prevent the plates from over closing and becoming jammed in the bores. This screw has thread locker on it and should not be touched but look to see of your mechanic has messed with it for some reason.
Other possibilities for a high idle are a problem with the TPS, the computer uses feedback from it to regulate idle speed via the IAC valve so both of these items must be in good operating order. And of course a vacuum leak or a gasket leak are possibilities especially if the intake or TB were removed or any vacuum lines were touched.. they get really brittle at this age.

 

Thanks, I will check the tb plates, also please clarify what TPS & IAC full names are so I can identify them and location on engine. Do you think that I should disconnect the battery for about a hour then reconnect it to reset computer? another person said to reset the timing, I don't think that is correct. Thanks for the help!

 

TPS: Throttle Position Sensor.
IAC: Idle Air Control.
Disconnecting the battery will only loose any stored codes and make it harder to find out whats wrong.
Messing with the timing will make things worse,

 

Thanks for the sound advise...Iam working on it...will let you know what happens.

 

I would suggest using Motorcraft parts if you are able to afford them.
Shopping online for Motorcraft parts can be a better option if you are able to wait for them.
,
As the previous poster suggested:

• Check your TPS and make sure it is within specs ( when I bought my van a few years ago, it would idle at 1500 RPMs, due to a faulty TPS)
• IAC
• Vacuum leaks are another possible cause of high idle speed
• Carbon build-up in the throttle body or sticking throttle body

Last, here is my personal experience with high idle speed.: My 94, E350,5.8L had been very inconsistent with the idle speed for the last year or so. This past June the computer in the van died.
I put a remanufactured computer and my idle speed is all within specs now.

Good luck.


.

 

I recently had low-idle problems on my 1990 E350 with 460 engine. My problem was a bad engine temperature sensor. Note this is different on my engine from the sensor for the instrument cluster.

Steve

 

Maybe someone can help to my issue to with good advice. I have 1989 5.0 EFI engine. Recently it has the problem that after some driving when i am going to stop it starts to work very rough and then stalls. It starts right up and it continues almost everytime i have to stop. I messed with timing a little bit, advancing gave some results it stalled fewer times but still does. Also the idle is a little bit too low for my liking.
Today i looked for some vacum leaks and found some vacum line that is in the front of the engine buy in the right corner and it leads to some roundish part that is connected tonright side of the radiator if lloked from the front to the engine. When i disconnect that vacum line engine gains a little rpms and strange stopping problem disapears. Anybody know what that part does ? So does my problem is more vacum related ?
I did not whant to run without vacum so i reconected it back.
For now i put the piece of tge fuel line rubber on adjusting screw in throttle body and now it idles at about 1200 rpm bit atleast i do not have stopping problem for now.

So do i have point to order new iac valve, tps or just disconect that vacum ? But then i maybe will loose some functional and needed part ?

 

Also someone mentioned ecu unit going bad. What is the differencies between federal emmison california and high altitude emmision units ? Who has more power, better emmison levels ?

 

Here is the part.

 

I'm lost where you are in the engine compartment but that big thing at the top of the picture with the cable coming out going to the bottom-right looks like the cruise control servo motor.

Steve

 

Thanks. Already thought it is cruise. So if i disconect it, should i feel the difference ? Not using cruise anyway