I had all these symptoms .I pulled the idle aircontrol solanoid and valve off and they were all gunked up with oil! so was the throttle body . I cleaned them with carby and TB cleaner paying particular attention to the idle air control valve. My guess is that under hard driving the breather from the rocker cover lets oil blow into the intake and it then got into the TB . seems fine now i cleaned it but its only been a day . I also disconnected the battery while i did it . dunno if this cleared the computer memory and helped or not .

 

I just fixed a very similar problem on my 92 F-150 Nite. I replaced the O2 sensor and clened the Idle control valve and I also added a light return spring to the throttle because I could see the stock springs weren't pulling it back like they should.

 

I have a book on how to clean the idle air control valve, i might do that. I'll replace the o2 sensor, and i took the intake tubes off and checked the return spring action and it works fine so it isn't the springs.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Justin - One Happy FTE Member

 

Well, turns out I can't clean it. My manual shows two idle air control valves, a cleanable one and a non-cleanable one. I have the non-clean able one. What should I do, test it to see if it's working properly? How do I test it?


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Justin - One Happy FTE Member

 

Check the wiring for your coolant temp sensor- if the comp. thinks it's really cold, it will up the idle. I would say it is a definite problem with electrical, rather than vacuum. The way these things are wired up is so that you can't be doing a brake stand. My Yota did this to me- with the brakes on, it dropped the rev limit to 1600 rpm- no joke! If you sit there for more than a few seconds with it idling high, it would start surging then cutting out.

 

I forgot to mention I had also checked and replaced my temp sensors. There are two on my truck. One is for the gauge and the other is for the computer. The one for the gauge went out so, I replaced them both and the truck ran better after that but, still not right until I changed the o2 sensor and cleaned the IAC valve and put the spring on. The IAC I have looks like a tube with two holes on the side that connect to the TB by a flange. All it is, is a diaphragm with a rod that rises or falls according to engine vacuum in the TB. When I opened it up, it moved smoothly but, I gave it some carb cleaner anyway. Does the manual say why you can't clean it? My TB has a sticker that says not to clean the TB itself or anything around it. I laugh at such stickers. I removed the TB and cleaned it thoroughly. Have you checked your coolant lately? If it is very rusty, it could have clogged the lines that cool the TB. If yours is like mine, it has coolant lines that feed coolant through it so it maintains a constant temp. If those are clogged, it could cause the engine to think it is cooler than it is.

 

It doesn't say why, but it shows the two in a picture and mine is the non-cleanable one. I guess it's more complicated.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Justin - One Happy FTE Member

 

It's probably non-cleanable to keep service employees employed!

 

I just got my ram air kit working and it has seemed to improve this problem a bit, but still not where it's suppose to be.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Justin - One Happy FTE Member

 

Well I just tried to clean out the Idle Air Control Valve with some carb cleaner. It was dirty and gunky but didn't fix the problem. Mine is the non-cleanable one but you can clean it a little. You guys thing I should replace it? Or start looking somewhere else?


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Justin - One Happy FTE Member

 

I know you said you checked the return springs but, I still think it might be the problem. Here's my reasoning. Usually, the way we check the springs is we grab the throttle and pull it to rev the engine and then let go. The problem with this is we are moving the throttle a long way relatively. You say it only happens around 2500rpms. In throttle distance, this is a verrrrry small space. If you were to open the throttle to this rpm level, then let it go, it probably will show you it isn't actually closing the throttle all the way. I would request you try a simple test. Go to your local home depot or lowe's, etc. Find a spring that isn't too strong but, firm and a good length. You will see that once you remove the cover over the throttle, there is a hole for something on the throttle. Hook the spring there and in the hole for the screw that held the cover or just fit it around the large opening on the mounting plate. Drive the vehicle for a while and see if it makes a difference. You should feel a little extra resistance at the pedal. If not, you should get a stronger spring. If it doesn't work, your only out a buck or two and a few minutes work and you have eliminated one possible cause from the list. Let me know how it goes.

 

I'll give it a try, thanks.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Justin - One Happy FTE Member

 

By the way, if I just rev the engine up to 2500 and let it come down, it will come down quickly. But if I shift at 2-2500, it will slowly come down so it has something to do with having a load on it.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Justin - One Happy FTE Member

 

First of all, you don't throw parts at an EFI system and expect to fix anything. You also cannot troubleshoot one over the internet. Quit being such a tightwad and go buy a $40 code scanner and do an Engine Off and Engine Running test. I've never needed anything more than one of these scanners to pinpoint a problem. Incidently, you blew off the guy that suggested the throttle position sensor. These are notoriously flaky on these engines, but hey, I'm sure that's not what it is since you said so. Also, feel free to "laugh at such stickers" and hose out your throttle body with whatever you choose. That sticker isn't there to keep you from ruining the delicate coating inside the throttle body and IAC valve or anything else important like that. It's really just just to protect the service tech's job in much the same way that the DO NOT SMOKE signs at the gas pumps are there to protect the ambulance driver's job.

 

>First of all, you don't throw parts at an EFI system and
>expect to fix anything. You also cannot troubleshoot one
>over the internet. Quit being such a tightwad and go buy a
>$40 code scanner and do an Engine Off and Engine Running
>test. I've never needed anything more than one of these
>scanners to pinpoint a problem. Incidently, you blew off
>the guy that suggested the throttle position sensor. These
>are notoriously flaky on these engines, but hey, I'm sure
>that's not what it is since you said so. Also, feel free to
>"laugh at such stickers" and hose out your throttle body
>with whatever you choose. That sticker isn't there to keep
>you from ruining the delicate coating inside the throttle
>body and IAC valve or anything else important like that.
>It's really just just to protect the service tech's job in
>much the same way that the DO NOT SMOKE signs at the gas
>pumps are there to protect the ambulance driver's job.

I didn't think it was the TBS because I didn't have the same symptoms as him. I know I am not suppose to "just throw parts at an EFI system", thats why I'm trying to troubleshoot before I buy a part. My idle air control valve is the "not cleanable" type, therefore I figured it would have to be replaced if there was something wrong with it. I don't see why you can't troubleshoot one over the internet, I'm doing ok so far. Sure it's more trouble but it can be done. A code scanner is $40 dollars out of my pocket that I'm trying to prevent the loss of. I don't like to throw my money out when I don't have to.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Justin - One Happy FTE Member