IAC Check

[KYRangerDude]

I was wondering if this is a good check for the IAC on my 2.9?

While engine was idling, I pulled the electric plug off the IAC...the engine almost died, but I quickly plugged it back in and engine idled back up. Since the cheapest IAC I can find is around $60, I didn't want to spend that on something that may not be the issue. I've cleaned the IAC with MAF cleaner and all, but nothing changed. I just check mpg and I'm getting around 15mpg, I'm thinking I should get somewhat better...perhaps 20+ mpg.

New plugs, wires...I got a new fuel filter to put on when I can get the stupid bolts/nuts off the cover. How do I check the fuel pressure? I read on here about the valve on the TB, I think I know where it's at...it's got a cap on it, can I use a tire gauge to check pressure? How do you check the pressure? There's probably a tech page on it, but I've not found it yet.

 

[jhammel85]

I was wondering if this is a good check for the IAC on my 2.9?

While engine was idling, I pulled the electric plug off the IAC...the engine almost died, but I quickly plugged it back in and engine idled back up. Since the cheapest IAC I can find is around $60, I didn't want to spend that on something that may not be the issue. I've cleaned the IAC with MAF cleaner and all, but nothing changed. I just check mpg and I'm getting around 15mpg, I'm thinking I should get somewhat better...perhaps 20+ mpg.

New plugs, wires...I got a new fuel filter to put on when I can get the stupid bolts/nuts off the cover. How do I check the fuel pressure? I read on here about the valve on the TB, I think I know where it's at...it's got a cap on it, can I use a tire gauge to check pressure? How do you check the pressure? There's probably a tech page on it, but I've not found it yet.

IAC sounds like its working OK. You said you cleaned it out but did you completely tear it down and clean it out? It makes a world of difference.

To check the Fuel Pressure you need a gauge. Should be around 40 with the key on, engine off. 30-35 with it running. 5lbs-10lb drop or so leak down after its off.

15mpg seems kind of low but it really depends on your driving habits, tire size, trans, gearing, mileage, etc.

As a reference, My 87 with a 2.9, 4x4, auto, 30.5" Tires, 3.73's and 147k on the clock gets about 18-20 mpg as a mix of both highway and city driving.

So what's actually wrong with the truck? Just the MPG? Let us know what kind of symptoms you are having.

 

[KYRangerDude]

92 Ranger 2.9 auto 4x4 145K

It doesn't idle right....Now that the rpm gauge is working...it's idling around 600 but sometimes it goes to around 900 and then down to 500. Sometimes dies when you give it fuel too fast...like I have to ease the pedal down. This is from a cold start, after the motor warms up, it's not soo bad. It doesn't sound like it's missing or anything. I suspected vacuum leak, but I've checked the hoses. I'm thinking about replacing the vacuum hoses. There's not that many. Wonder if you can buy the little hard plastic hose or will I have to replace with the rubber hose? There is one hose that comes off the TB above the fuel regulator that runs the firewall over to where the heater hose enters the cab, then turns towards the fender well and gets with some wires and is wrapped with them going somewhere. I haven't been able to run it out. I have no idea where it's going. Seems like a long way for a vacuum line. I can pull the vacuum hose off going to the air filter and it seems to smooth out a lot better. It doesn't use oil, not leaking now..after I changed valve cover gaskets. Doesn't smoke. It actually sounds really good when it's warmed up. And probably not as bad as I'm making it sound on a cold start, but I can tell it's just not idling right. It does have an exhaust leak on the manifold near the #4 cylinder, hairline crack, and I can hear it. I've got to repair/replace that when I have the money.

I pulled the IAC off and just sprayed it a lot with MAF cleaner. All kinds of black soot came out...I didn't attempt to tear it apart, I wasn't aware that you could. I took off the air hose going to the TB and sprayed up in the TB, again, all kinds of soot came out. I sprayed the MAP/MAF whichever one it is I have. Not much there actually. Put it all back together after letting it dry out a bit...started it and white smoke every where...actually was a little concerned...but it cleared up and didn't notice much of a difference in idle.

MPG may improve some now that I've changed from auto hubs to manual. But something just isn't right with the idle. I pulled a code 12, but it didn't tell me how to "fix" the problem. * Cannot control rpm during self test high rpm check.* I also pulled a code 77 * Operator error ( Dynamic Response/Cylinder Balance Test) I thought I did it correctly...turned the wheel, slammed on the brakes, and floored the gas pedal...but I attempted 3-4 times and it always came up same codes....12 and 77. I figured I wasn't doing it right and just gave up. But now I"m wondering if they actually are the issue I"m having....but without any guidance the codes mean literally nothing to me. LOL

 

[jhammel85]

Sounds to me that the TPS should be adjusted. The Idle is way too low. Even though the ECU controls the Idle, it's base line is determinded by the screw on the TB.

http://www.fordfuelinjection.com/?p=30

Since its an auto, it should idle around 850 rpm warm. Somewhere around 1200 when cold.

Check that out and it will adjust the idle. See if that helps 1st.

Also, somewhere on here someone mentioned how to calibrate the IAC but I've never tried it. Try searching for IAC under the 2.9 forum and have a look...It'll help you track down the problem.

Hope that helps!