96 Explorer, hesitates at start up and at other times revs up.

[TapOut64]

Intermittently at start up my Explorer will idle really rough then at times after being driven for a while the tack will shoot up to 2,000 when stopped. I was putting my boat in the water one day, backing up, hit the brakes and she didn't want to stop, luckily the brakes out powered the higher rpm. Another time I noticed the tach at 2,000 while braking and nearly stopped, put it in nuetral and the tack shot up to 4,000, put back in gear and tach went back to normal. I had the IAC motor changed out but that hasn't helped. Any ideas?

[shorod]

When is the last time you had the Explorer tuned up? Which engine does your Explorer have?

You may want to consider adding a bottle of fuel injector cleaner to the fuel and changing out the fuel filter.

The rough idle could be due to an issue with the EGR system (as well as many other items). If the EGR valve is not closing completely at idle, it could lead to difficulty maintaining an idle. Also, if the DPFE sensor is malfunctioning, it may contribute to this issue. The DPFE is a fairly common sensor to fail on Fords.

You may also want to carefully clean the Mass Air Flow (MAF) sensor elements and make sure the intake air hoses are all snug and properly installed. Any unmetered air entering the engine could cause driveability issues as well.

-Rod

[sparkslg]

What work has been done to vehicle ? what engine? Where did you get the Iac from ?


I would be checking for a vacuum leak or another area where air is not metered , ie. intake tube from air cleaner cracked ,
Not so much concerned with egr unless you have a rough running engine . Definitely not DPFE sensor .
Check PCV and that hose for a leak , has the pcv valve been replaced , where is that from?

[TapOut64]

Had the intake manifold gasket changed and that seems to of taken care of the high rpm problem. The hesitating is really intermitent and seems to only happen when theres around a 1/4 tanks of gas so I'm going to try to keep it above 1/2 full and see if it messes up. It hasn't so far.