Hello All,

I've been lurking around here for quite a while, just have never registered until today since I actually have a problem of my own that I need some advice on.

I have a high idle speed of approx 1100 rpm on my 2000 f150 5.4L.

I have replaced the IAC already, and have had no change.

I never get a service engine light on, and when hooked up to a code scanner, I get no codes.

Upon RESET using the code scanner, the RPM's go normal! (700ish) , for about a day or so (I'm assuming it takes this long for computer to relearn?) , there are 2 things listed under the emissions readiness check on the scanner that are "not ready" , which is EVAP , and EGR , It's AFTER those are ready, that the idle speed goes high again!

Any ideas on what I can do to narrow this down? I've heard some suggestions from friends about EGR valve possibly.

Not being a mechanic and having very little experience troubleshooting issues such as this, I'm hoping for some advice on what to do next?

Thanks!

Rob

 

I'd start off cleaning the mass air flow sensor. Easy. cheap. Theres a how to here
https://www.f150online.com/forums/ar...ml#post4193148

 

Sorry i forgot to mention that I cleaned the MAF sensor when the IAC was replaced using that exact post as a guide.

Rob

 

Check both the EGR and evap systems for vacuum leaks.

 

Yep, -the PCV line, - back by the firewall. They can develop pinholes with age. Eventually getting bad enough to thro lean codes.

I'd pull the throttle body and elbow. Clean everything up well. It will be easier to scope out the PCV system anyway , -once the body and elbow are pulled.

Disconnect the battery before working on anything this time, -don't ever forget to do that. - Do it right, - no need to rest with a scanner. I wouldn't do that.

 

Ok I sprayed the heck outta my MAF with Sensor Klean , and went for a drive and the rpm's stayed normal for a day or so, now the high rpm's are back up again!

Can't find any vacuum leaks, on the weekend I'm thinking of pulling the throttle body and cleaning it...

Any other ideas?

 

Did ya check the pvc elbow at the back of the throttle body like jbrew said? Do that then clean the throttle body while your at it. That never hurts fact is your truck will run better when you do that no mater what.

 

And you have to clean the MAF, spraying it doesn't get it lol. Then reset the KAM.

Oh well, your not listening to well anyway.

 

I followed the instructions you linked for cleaning the MAF sensor, The elbow at the back of the intake that the pcv valve hose is connected to appears to be fine, all the other hoses appear to be in good condition and no vacuum leaks were found.

I plan on removing and cleaning the TB tommorow morning.

Rob

 

How else would I clean the MAF sensor? I thought the wires were not to be touched, just sprayed with a maf sensor cleaner (After removing it from the assembly of course)

 

Well, I don't use MAF Cleaner. It's all marketing hype and leaves a cloudy residue. Just like other CRC products do. I've never broke a wire cleaning the MAF wires by hand. Either with Denatured Alcohol or a Paint prep, such as Duplicolor Paint prep.

There's been occasions when the MAF may have a hard shell that's been cooked onto the wires over time. Spraying won't cut that shell. You have to cut that with Lacquer Thinner , CAREFULLY. When using Lacquer thinner, you have to avoid rubber and plastic. Only use that if you need to. You can't always see (visually) that the MAF is indeed dirty. If it shines up w/alcohol, -that's all that needs to be done.

It's not hard to do. I use a little hobby brush and paper towel. You can twist the paper towel to size and polish those wires along with any of those agents listed above to assist.