First, I have little experience fixing vehicles. But I have replaced shocks, alternators, belts and stuff like that in the past and we don't have money to be paying for repairs if I can fix it.

My mother's 96 F 150 has had an erratic idle for a while. The mechanic says it's the Idle Air Controller but said it's not necessary to fix it.

The weather in WI has been below zero the last few days and the gas pedal has been sticking. If we warm it up, sometimes it will relax a little, but not all the way. It is hard to push in and comes back out VERY slowly.

I traced the cable to the Throttle body and lubricated the three springs that seem to provide the tension. I also got a can of carb cleaner and sprayed out the intake a little. The butterfly valves seem to be fairly clean though. I can see metal with just a little varnish all around.

I can't figure out how to easily isolate where the stickyness is. There is the cable to the pedal and also one to what I imagine is the cruise control box (small box with cable to the throttle and lots of wires on a harness to it) or possibly the IAC.

We are expecting snow tonight and need the truck to get her to work until the plows come through. So I kind of need to fix this tonight. :-(

Oh, and it's about 5 below where I have to work on it... No garage.

Any ideas where I should start? Can I disconnect the cable that doesn't go to the gas pedal if that's the problem? Or is it necessary?

Thanks for any advice. -Dav

 

Ok, I got the cables disconnected from the throttle (just pops off a post like a ball hitch) and they are OK. They move very freely. The throttle however is quite sticky. I imagine it should spring back pretty much instantly. It doesn't move at all without pushing it back. But the springs seem intact. It's just too much friction.

I don't know if I should try to clean the outside where the springs are, or focus on the inside where the valves are, or both. Should I attempt to remove the whole TB and take it inside where it's nice and warm to get it real good and clean? Or am I risking disrupting some seal or something by removing it?

 

Sounds like you need to take the TB off and give it a good cleaning insied and outside. The removal should be fairly simple. I woild make sure I had a replacement gasket on hand first. To clean the inside, you need to get some TB cleaner that is safe for coated TB's if needed. You might need to get a soft brush ans scrub the inside of the TB, especially around the butterfly valve pivot points and ensure the other ports are clean also.

 

Replace the IAC

 

I took the TB off and it's an older one, 96, so I don't think it's coated. The parts shop only had carb cleaner that said it was safe for this use. It was coated pretty good inside, but the real problem was that one of the two springs on top was broken and doing nothing and the post it spun on was so gunked up that it wouldn't have worked if it had spring tension anyway.

So I cleaned that all out and got inside the IAC as well as I could also. But I think the IAC just needs replacing if it still causes problems. It's too hard to really clean it well and there's some pretty good grit in there keeping the spring from compressing right.

Tomorrow is supposed to be warmer (20 Degrees, but probably snowing). So I'll try to put all the hoses and wires back together properly and see how it flies. There is a ton of gunk in the intake of the engine too. I'll have to clean that out. I'm guessing that's why the thing is usually so gutless. The gunk seems to be more than 1/4 inch thick and the holes where air should go are far from the shape the metal under the gunk is.

Hopefully I'll be able to clean that out without taking anything else apart. But if fixing cars is like fixing houses, there's always something to fix that's just one step farther than you already have gone.

Thanks for your help.

 

Yea , you have to work the mechanicals inside the IAC while cleaning. Without compressed air, cleaning is almost impossible to do effectively. It takes a quick shot and blow of a harsh carbon cleaning agent to do well. If this doesn't get blown out, you can compromise the sensor.

Sea Foams "Deep Creep" is the best for this IMO. If you don't have air, use that stuff. - De-carbons and lube's as well.

 

Well, it's back together now and started up like a charm the first time. Ran nice and smooth too.

So I went to put the air intake hose back on and started it again. This time it just kept choking out. It wouldn't stay running without throttle.

I took the hose off. Same problem. So it's not an airflow restriction there.

Guessing that the IAC was open the first time and closed and got stuck the second time, or that the sensor that controls it told it to stay closed, I just opened the throttle's idle point about 1/4 to 3/8 to let some air in.

Now it idles and stays on. But it's really rough and seems to be missing. So I'm thinking that either it's getting too much gas from whatever sensor tells it the mix of gas to air. Or I clogged up the engine with some of that gunk from the manifold.

I couldn't see all the bolts needed to take off the manifold and I have nothing but a basic set of tools and a poor place to work on the truck in the back yard in the cold and snow. So I didn't tackle taking it off to clean it well. I just pulled out what gunk I could get to at the intake.

So, the question is what's likely causing the really rough idle? And can I correct it without spending more money? I can probably drive it in to a mechanic nearby. But I wouldn't yet trust it to be my mom's daily driver.

She only goes 4 miles a day. How can I make it work for her until we get more money?

 

Check voltage /Replace the IAC.

 

Well, I think it's all working well now. It seems I had discounted the need for the Mass Airflow Sensor to be getting a reading. I didn't have the intake hose connected for most of my testing...

I put that back on and adjusted the idle screw until it had a nice engine speed and it's running beautifully with a nice and responsive throttle pedal that she probably hasn't enjoyed in a long time.

Thanks for all your helpful input. It's people like you guys that make it a pleasure to take on challenges that could be quite frustrating for a novice.