Rough idle - only for 1 or 2 minutes - 4.0 OHV

[Jim Jermain]

I have a 2000 Explorer with the 4.0 OHV (70K miles). On cold starts the idle is fairly rough for about one or two minutes, and then it smooths out and runs great. I tried changing the plenum gasket; (I did not change the gasket between the fuel rail and the intake. The vacuum is very steady at 22. I also tried cleaning the Mass Air Flow sensor and running a can of Sea Foam through the engine. I also thought the problem might be with the idle air control valve so I pulled that off and cleaned it out. If I disconnect the idle air control valve with the engine running, it almost dies, so I suspect it is functioning. I've also replaced the thermostat and the plug wire were replaced. Any suggestions? I am stumped. It's not bad but my wife complaints about the rough idle. Got to keep her happy!

Thanks,

Jim

 

[REDDY]

bring it to advance auto parts store, free obd2 reading, see what codes it give

 

[Jim Jermain]

Thanks for the tip. I forgot to mention I have a code reader and I checked the codes. It came up empty. No codes stored.

Jim

 

[ivrb]

I have the same deal with mine also a 2000 4.0, let me know if you find out please.

 

[Jim Jermain]

will do,

Jim

 

[Tavery1]

Did you actually clean the IAC valve? If you didn't go to Autozone and get some electrical cleaner. Did mine this morning and it helped quite a bit heres a nice breakdown the IAC on 98 Explorers SOHC's are underneath the plastic cover fyi http://www.explorer4x4.com/iac.htm. I'd also clean the mass airflow sensor and possibly the throttle body.

 

[huntersteve61]

Just a thought but mine did this and it was an oxygen sensor. Light came on some time after the rough idle. at cold it wasn't working quite right. Id suggest trying that. I also have found that maybe you have a problem with fuel delivery? Just a suggestion...70K it really shouldnt' idle rough thats not a whole lot of miles. Let usknow what you find. I thought sea foam was god haha

 

[Tavery1]

Just a thought but mine did this and it was an oxygen sensor. Light came on some time after the rough idle. at cold it wasn't working quite right. Id suggest trying that. I also have found that maybe you have a problem with fuel delivery? Just a suggestion...70K it really shouldnt' idle rough thats not a whole lot of miles. Let usknow what you find. I thought sea foam was god haha

The o2 sensor is a good idea, it could be that but no disrespect it would be best to try cleaning as its the cheapest and easiest fix.

 

[Jim Jermain]

Thanks guys, these are all good suggestions. I tried cleaning the MAF and IAC a few months back. I think I will try all three and see if it helps. I'll keep you posted.

Jim

 

[Tavery1]

If cleaning the sensors and throttle body don't work you may have to replace the intake manifold gaskets a friend of mine had a very rough idling Explorer cleaning didn't work so he changed the gaskets, problem solved. Good luck

 

[Runnin'OnEmpty]

I agree with it being the lower intake gaskets.
They leak coolant into a cylinder (usually #4),
after sitting overnight and causing a missfire
the next morning.

 

[Jim Jermain]

Very interesting, I noticed my coolant was a little low. I wonder if they are related. I'll look at the lower intake manifold gasket. Should be a good weekend project.

Thanks again for all the advice.

Jim

 

[ivrb]

Did the replacement of the lower intake take care of the problem, I have the same issue

 

[2000StreetRod]

fuel filter

I suggest that you change the fuel filter if it hasn't been replaced in the last 30,000 miles. See http://www.explorerforum.com/forums/showthread.php?t=257948

 

[cheeech]

ANy luck on your situation? I'm in the same boat. I've dumped Lucas injector cleaner in the past few fill-ups and nothing. Ive tried seafoam and got barley no smoke. I've cleaned my T/B, MAF, IAC valve, New plugs, Wires are new, Coil pack is newer.
My idle has almost a stumble to it when fully warm(idles 900ish) Just rough enough to notice when warm. It's super rough when cold for the first 20-30seconds and then smooths out.
Maybe a leaky injector? i think it runs rich because the best mileage i can get is 280miles per tank on the highway.....yuck!
Leaky injector/injectors would cause rough stumbling cold start i would imagine???