rough idle 2008 v6 explorer

[goose543]

I have a 2008 explorer v6 60000 miles the truck about 2 weeks ago stared with a rough idle replaced fuel filter and plugs still have rough idle then put it on snap on reader had one code bad crank postion sensor. Replaced the sensor still have the rough idle. The snap on computer said rough idle no codes look at EGR valve it should not be hot to touch at idle well it was replaced that, still have rough idle. Any help on situation

 

[Flag Gibby]

Well, really only 2 things left so clean the MAF sensor and the throttle body. I guess that it could be a plug wire breaking down or the coil pack, but the wires and coil pack are very reliable so I have a hard time thinking that those items are at fault.

 

[goose543]

There should be a miss fire code if plug wires or coil pack is bad going to clean maf sensor on tomorrow. Thanks

 

[Old As Dirt]

Vacuum leak?

 

[TennesseeVol17]

Fix?

Goose, were you able to get a fix? Having the same problem and looking for help.

 

[engineeering]

You might also have a bad crank case pos sensor (the new one could be bad if you got a cheap ebay replacement). This is most likely because you would not get that code unless there was a problem with it.

Vacuum leak?

x2

If it's definitely a good crank case pos sensor... could be a vac leak. Is the rough idle cyclical? (does it slowly throttle up and down) If so... it's un-metered after air (not read by your MAF sensor). This will cause a rough idle without a code. Best way to find those (IMO) is to use a smoldering cigarette and/or hose... move the hose around the engine bay and wait for the hose to start sucking in smoke/air.

 

[TennesseeVol17]

Engineering,

I removed the MAF sensor electric port (left the sensor in the hose) and the problem continued, neither worse or better. Am I correct in thinking that means the MAF sensor is not functioning since it made no difference once I "removed" it?

 

[engineeering]

Engineering,

I removed the MAF sensor electric port (left the sensor in the hose) and the problem continued, neither worse or better. Am I correct in thinking that means the MAF sensor is not functioning since it made no difference once I "removed" it?

That probably DOES NOT indicate a malfunctioning MAF. Not sure how the ecu "corrects"... but if there is a big vac leak... your ecu will still try to run your engine. It causes a "cyclical" idle because it tries to correct the lean condition (caused by the leak) by adding more fuel... I'm guessing is then starts to lean the mix because it thinks it's richer than what it is programmed.

Is the idle cyclical?

 

[TennesseeVol17]

No, I don't believe it is cyclical. When I crank it, it goes to around 500-700 RPM and stays there idling rough. It does it again when I slow to a stop sign or light and it goes to 500-700 RPM. I took it to the dealer, but they could not find the culprit.

 

[engineeering]

have you had the problem for a while? Did you fill it up with bad gas? I think I got bad gas once because my vehicle ran way better on the next fill up.

The problem was only at low idle right? So not fuel pump... and you have spark. No misfire code? Did you scan it?

If you have a smaller vacuum leak this could also cause the problem (cyclical is usually a huge vac leak... ie a 1/4" diameter hole). There really aren't too many places you can get a vac leak... follow/check your red and green 1/8" diameter vac lines (one goes to the egr, don't know about the others), the brake boost hose, your big hose/rubber intake for cracks, fuel vapour return line, ... basically anything opening/crack that comes off of the big plastic intake manifold that could be sucking air in.

I usually find the small vac leaks by using a short hose against my ear and listen for them. If a leak is big enough it will suck air through the hose and you'll know right away.

Really hope you get to the bottom of it.