IAC Questions

[smegun]

at start up the truck idles high then backs off to a slow idle after about 30 seconds is normal roughness in any operation is a problem not the speed of the wake on period

I don't think you can do anything for actuall performance time that is when the engine is at a good temp to burn fuel ......... air and idle speed and choke doors are for keeping things from being to embarrassing from farts and sputters it was never intended to be a complete fix that is turnkey complete fix for aspirations



I put a new fan clutch in vroom vroom I put new sensors in dollars dollars I hit the gas octane octane

 

[smegun]

seriously im trying to figure performance issues for a ford circuit again.

....... on my 80 tbirds they both ran good but had the same problem with my 94 exp cant handle passing speed gas right I replaced everthing electrical once practically to find the problem was a hairline crack in my battery case it just couldn't get charged right could never seem to match up with its prevenative detune of the stroke timing the great thing with injection and electrical timing adjustments is you don't have to feather the pedal the bad is getting the circuit balanced

 

[mr cribb]

I took my IAC valve apart a few days ago and cleaned the carbon out of it with seafoam. While cleaning things I cleaned the MAF sensor. I also used seafoam through the vacuum line to clean the top half of the motor.

Between the two clean sensors and a cleaner top end my idle is at 650 at idle and no warm restart misfires.

 

[ranger7ltr]

What is your fuel pressure and how long has the fuel filter been on the truck?

The symptoms you are having can very easily be attributed to low fuel pressure either from a dying fuel pump/dirty filter sock on the fuel pump/clogged fuel filter under the drivers side of the truck...

When you change the filter see if you can easily blow through it... If it is difficult your filter was not helping your engine to get the fuel it needs to run well...Oh it WILL run just not like it should because it is running lean...I have a fuel pressure gauge on my fuel rail to see what the pressure is and when I had a dirty/rusty fuel tank I could tell when I needed to change the fuel filter as the pressure would start to drop even though the truck was running pretty well...

Unless you are getting codes referring to other sensors or conditions I would make certain the fuel system is delivering what it should be and then look at the other areas if they continue to be a problem...

Boy oh boy this is a revival. For what it's worth, I've learned a lot in the last year but I still have this issue.

IAT and ECT sensors replaced and tested within tolerances. Cold engine starts still falter, I've learned to deal with it by giving it gas while starting, that usually does the trick. I'm tempted to still buy a new IAC valve, they can be found cheap enough on eBay. But I think part of the issue may be injectors or bad check valve in the fuel pump. Sometimes it seems like my fuel rail is empty but priming extra times (key on, off, on, off) doesn't always help, it seems like there's something else going on.

I haven't given this issue much thought as there have been more pressing things to fix on my Explorer. I calculated my MPG to be 14.2 over 1,500 miles so something is still off. MAF & TPS seem fine, no need to replace. O2 was replaced too. That doesn't leave much left, except the IAC. If anything, my plugs look on the lean side and having to give it gas when starting it cold may mean that the IAC is leaking too much air into the engine. Hasn't thrown any check engine lights on me though.

I will say that my other suspect may be a bad lower intake gasket which might be sucking excess air in. I know I have issues with coolant leaking from the lower intake, so the intake ports themselves could be leaking too? That's on my to-do list.

I will figure it out in due time.

 

[natenkiki2004]

The symptoms you are having can very easily be attributed to low fuel pressure either from a dying fuel pump/dirty filter sock on the fuel pump/clogged fuel filter under the drivers side of the truck...

When you change the filter see if you can easily blow through it... If it is difficult your filter was not helping your engine to get the fuel it needs to run well...Oh it WILL run just not like it should because it is running lean...I have a fuel pressure gauge on my fuel rail to see what the pressure is and when I had a dirty/rusty fuel tank I could tell when I needed to change the fuel filter as the pressure would start to drop even though the truck was running pretty well...

Unless you are getting codes referring to other sensors or conditions I would make certain the fuel system is delivering what it should be and then look at the other areas if they continue to be a problem...

I've given thought to that. Replacing the fuel filter was one of the first things I did and it didn't make a difference. I wasn't expecting it to, I just wanted some easy preventative maintenance. My fuel gauge is acting a little weird at times. I know the previous owner replaced the pump but I don't know if the whole unit was replaced or just the pump itself. Down the road, I may be tempted to replace the pump assembly anyway just for good measure.

I did test my fuel pressure and it was acceptable but on the low-ish side and didn't seem to change with RPM at all. I know I have issue with the fuel rail draining so there's problems with leaky injectors or the one-way valve in the pump. I'm not sure what's going on exactly but the whole fuel system is pretty important and like I said, I may just replace everything so I don't have to worry about it for a long time.

I have no running issues, I can sit at 3,000 RPM for a while and drive long runs on the highway. Warm startups seem to be fine now. Cold starts are troublesome, I usually feather the throttle while cranking and it catches. It does idle weird when cold, RPM doesn't go up right before shifting out of park like it should but it does when warm.

The truck's got issues, I'm working on the more serious ones, one at a time