Hey everybody, this is actually my 1st post but I read this site almost daily. Lots of good info here. I guess I'll say something about myself first of all. I just got back from Iraq not too long ago, SSgt in the Air Force. I've been stationed in Germany for 2 years now, it's a very nice country. I mess around with Satellite Communications systems in a combat unit for a living. It's definitely not the regular AF, more like Army/Marines field work. Lot's of fun. I have a 95 F150 5.8L.

I guess the trouble is this... I run a KOEO scan and I get no faults, 111 System Pass. I run the KOER and I get some faults. 311 and 314- "Thermactor Air System Fault". I was prompted to run a scan because the truck runs like **** after 10-15 minutes of driving. I have no real problems when I'm just accelerating. Only problems are when I come to a stop. There's no tach, but I noticed the engine idle fluctuate between Low and Normal and watch the Volt Meter fluctuate. It does this until I accelerate again. Seems like the engine wants to die out. Before I ran the check engine scan I changed the fuel filter. I thought the engine was just being robbed of fuel somehow. No changes with the truck running like crap. But glad to know that it's changed out, the filter looked old.

I have a Chilton manual, it's not so great and confuses me more than anything. I have located the Thermactor and Air Pump. Looks like just a hose connected to valves, nothing too complex. Maybe the valves have possibly failed? Getting parts out here is next to impossible, I order online mostly. Just wanted to ask here first before I started messing around with it. See if anybody out there had some experience with this problem.

 

If anyone is interested... I think I may have found the problem. I was checking to see if all the hoses connecting with the Thermactor valves were OK. One of the small hoses had a hole in it and actually just crumbled in my hand when I disconnected it. I'll see if a new hose actually corrects the problem.

 

You may also look into cleaning the IAC. It controls idle while the throttle plate is closed.

 

I cleaned the IAC when I first bought the truck. Eventually I did replace it. Things seemed to slightly improve, but I don't think it ever was the cause of the main problem. Good thinking though.

 

Welcome to FTE

T/E = Thermactor Emission = smog pump and related crappola.

 

OK, I changed out that messed up vacuum hose. So I did another KOEO and KOER scan. No faults. That's good. I took it for a test drive and my problem with the erratic idle came back. When I returned home, I sat in the driveway with the truck in Drive and my foot on the brake. I sat maybe 5 minutes. I saw the problem go away (smooth idle) and then come back maybe 2 minutes later. Strange, I'm stumped now.

 

remove iac and replace with a new one.

reset computer after every major change.

 

SOMETIMES a worn timing chain will cause the idle to move back and forth between good and bad. Usually a high-miles issue.

Pull dist cap.

Rotate crank by hand until rotor moves.

Reverse rotation and see how far the crank moves before the rotor does.

1/8th turn is a lot when you figure it's 45 degrees of crank rotation....think moving the timing 45 degrees would make a diff...???

Long shot, but it pays to check everything.

 

The IAC is practically new, I'm not changing that out again. I did reset the computer though. And I let it idle in the driveway for 15 minutes. Drove to work this morning and saw no problems. But this has happened before. I'll continue to monitor the situation.

 

I was driving around running some errands and the Check Engine light came on. When I got home I pulled the codes. Codes 172 and 176 both pertain to Lean Fuel mixture.

I searched the forums and found a myriad of possible problems. Things like EGR, PCV, Fuel pressure regulator. For some reason I'm leaning towards the fuel pressure reg. Seems like a lot of others on the forum have had problems with this part. And also sounded like there was a recall for this part. From what I read, it looked like FPR doesn't connect to the computer and won't spit out a code.

I've been meaning to replace the PCV for a while now. It's in a bad location, but I plan to change that out today. I doubt that will fix the problem, but the one on it now looks old. Worth a try.

 

where did you buy the iac when you replaced it?

 

I ordered a Fuel Pressure Regulator and it finally came in the mail. Very easy to install, and it seems to have corrected the problem. The surging hasn't come back since. Thanks for everyone's replies.

 

that's great.

hope surging stays away for good