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'96 Ford Explorer; rough idle

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Apr 14, 2006, 6:28 PM

Post #1 of 12 (21268 views)
  post locked   '96 Ford Explorer; rough idle  

I have a 1996 Ford Explorer with a 4.0 engine. I am having issues with having a real rough idle after the motor is warmed. When the engine is cold there are no issues at all. I have had it in to a dealer and other garages who say they can't get the truck get the engine to run rough or simply can't find the problem at all. I have been told it could be a bad air filter (I don't think so!!), fuel filter (again.......I don't think so) and other suggestions. One thing no one has mentioned to me is the possibility of fuel "leaking" into the engine after the motor has been shut off, thus "flooding" the motor and causing it to run rough after a short period of being turned off. I have a Chevy that had that problem and when the motor was hot and restarted a brief time after it had been shut off, the engine ran really rough. I had the fuel regulator (I think that is what was fixed) replaced and haven't had the problem since. I am thinking this might be the same issue on the Explorer too. Since I own Chevy's (the Ford is the wife's truck) I am not real familiar with what or where the problem may be. Anybody else have any ideas?

Tom Greenleaf
Ultimate Carjunky / Moderator

Apr 14, 2006, 7:24 PM

Post #2 of 12 (21252 views)
  post locked   Re: '96 Ford Explorer; rough idle  

I'm shocked that a dealer just said air filter or fuel filter.!! Is a "check engine" light on? I'm just guessing but I think a sensor for engine temp is faulty and keeps telling the vehicle is cold when it's warm. If ok when cold and rough when warm it's almost certainly NOT just an air filter or fuel filter. You may need these but they shouldn't be just when warmed up?

Best I can say for now is make sure the wiring near thermostat is hooked up right, and the housing for the air cleaner is all together and on right. You can check your own air filter. Did this happen in front of mechanics? If so and that's the best they could do you need another place. T


Apr 15, 2006, 7:45 AM

Post #3 of 12 (21246 views)
  post locked   Re: '96 Ford Explorer; rough idle  

Pirate Yes the "Check Engine" light is on. We have had that looked at as well and been told ( a dealer) that the code read a bad EGR sensor/valve. It does periodically go out by itself but it does come back on after no more than four or five days. It primarily is almost always on. The light hasn't gone out for quite some time now. I have replaced the EGR valve but that did nothing to stop the "Check Engine" light from coming on after it was reset. Mechanics have also told me they have read a code which indicated a misfire with the spark plugs or ignition pack so I have replaced the plugs, wires and installed a brand new OEM ignition module on it (all at the same time). The truck did seem to start up and run better but did not eliminate the rough idle after the engine is warm. I did find a chipped piece broken off on the air filter box about a year and a half ago. When I replaced that it did help a ton with the way the truck ran. But, again, did not eliminate the rough idle.

As for the mechanics...........way ahead of you!! Haven't been back yet!! I do replace filters, plugs, wires when needed. I is stuff you need and everyday wear and tear is expected but I was astonished when I was told what "the problem" was!!!! Granted, they probably noticed the chipped air filter box but a piece of tape over the hole, temporarily, should have eliminated that as the "main" cause of the problem. I'll check the thermostat and see what I can find and get back to you. If you can think of anything else feel free to post it. I will check back.


Apr 15, 2006, 8:15 AM

Post #4 of 12 (21242 views)
  post locked   Re: '96 Ford Explorer; rough idle  

I took a few images from the thermostat housing on my '96 Explorer. There are two "plugs" (one on each side) of the thermostat housing. These are the only wires going to it that I can find. They appear to be in pretty good shape. I am wondering if the two plugs (one or both) could be the problem and if you can identify what they are or their function. The image titled "thermostat1" is on the left side (as you stand in front of the truck) of the housing (I took the boot off) and shows the "threaded" post atop the plug. The image titled "thermostat2" is on the right side of the housing. It can be seen dead center of the picture, (I am holding a silver flashlight in the upper right of the picture). Maybe these are the culprits? Let me know what you think.
Attachments: attachment icon thermostat2.JPG (130 KB)
  attachment icon thermostat1.JPG (126 KB)

Tom Greenleaf
Ultimate Carjunky / Moderator

Apr 15, 2006, 9:00 AM

Post #5 of 12 (21238 views)
  post locked   Re: '96 Ford Explorer; rough idle  

The monitoring devices near the thermostat tell two things at least.

1. One will be for your gauge or light for overheat condition.

2. The other tells the vehicle's computer the engine is warmed up and should reduce the fuel amount like a choke shutting off.

Wish DanD could catch this one but I'll give it a try. Unplug one and see if the gauge quits working. If so the other is more suspect. Get any codes first as that will make new ones for a while. I'm not sure about this problem - just a shot. If that part is cheap try it. I hate suggesting to just start throwing everything out but from a keyboard without a vehicle in front of me it's almost always guessing. Good luck with the fix and tell us what fixed it for the world to know. T


Apr 15, 2006, 5:33 PM

Post #6 of 12 (21229 views)
  post locked   Re: '96 Ford Explorer; rough idle  

Unsure I did a scan of the trucks system and came back with error codes P 153 and P 420. I have no idea what these codes represent. Do you have any knowledge of these error codes?

Veteran / Moderator
way2old profile image

Apr 16, 2006, 4:40 PM

Post #7 of 12 (21225 views)
  post locked   Re: '96 Ford Explorer; rough idle  

Diagnostic Trouble Codes (DTCs) P0133 and P0153 indicate the response rate of the HO2S is below some calibrated window.
DTC/HO2S Reference List:
  • DTC P0133 = HO2S-11
  • DTC P0153 = HO2S-21

Possible causes:
  • Contaminated HO2S.
  • Exhaust leaks.
  • Shorted/open wires.
  • Excessive fueling.
  • MAF meter.
  • Air leaks.

This is from the Ford Manual. Your code is for the rear sensor, behind the converter. The P0420 is a code for the converter below efficiency limits. Any of the problems listed above can cause the code for the converter also. If you are handy with a multi meter, I can post the info needed to test the codes.

Being way2old is why I need help from younger minds


Apr 23, 2006, 7:30 AM

Post #8 of 12 (21215 views)
  post locked   Re: '96 Ford Explorer; rough idle  

I sent an e-mail to friend of my dads who is a Ford mechanic. He mentioned there could be a possibility of the catalytic converter being blocked up which may be causing some back pressure to the engine. He said they would have to run tests to determine for sure but that is what it sounds like could be the problem.


May 14, 2006, 8:52 AM

Post #9 of 12 (21192 views)
  post locked   Re: '96 Ford Explorer; rough idle  

Well, I have one of the O2 sensors replaced. That took care of the rough idle in the truck. Now I just have to figure out how to get the second one on. It is right in a spot on the pipe where you can get a wrench on it but there is not enough room to get your hand on it ti turn it loose. I may have to reach through the wheel well and remove the fender liner to get at it. What a pain!!! I was looking at it and was thinking I might be able to remove the pipes off the manifold to get at it. I'm not a mechanic so I don't know if that would screw anything up or not. Would that be ill-advised to do that?Unsure

New User

Jul 18, 2007, 5:52 PM

Post #10 of 12 (20879 views)
  post locked   post icon Re: '96 Ford Explorer; rough idle  

i have a 96 ford explorer as well and it seems we are having similar problems. however i wanted to ask you if yours is maybe doing some other things mine is. when it idles, its shakes and smells funny, and it gets really really hot. I hear a knocking sound from the engine, and i just changed the spark plugs about 3 months ago. I heard there was a recall on some of the 96 ford explorers due to different problems, so i can also suggest you call these numbers i got from the internet. One is for Ford and it's 1-800-392-3673 and the other is an Auto Safety Hotline 1-800-424-9393.

Please write me back and let me know! I'm desperate to fix my truck!!!!!! CrazyCrazyPiratePirate

BTW mine also runs better in the cold. When the temp outside is over 90 the truck runs horrible!!!!!!

New User

Apr 27, 2012, 5:51 PM

Post #11 of 12 (11505 views)
  post locked   Re: '96 Ford Explorer; rough idle  

you know i read your message and i am having the same problem with my 94 explorer and i haven't figured out the problem either the only thing is my explorer check engine light is not comming on it's like its flooding itself out and i am suppose to be taking mine to a dealer on monday so if you have any other ideas what it could be i will gladly take suggestions thank you for you information and have a nice daySmile

Tom Greenleaf
Ultimate Carjunky / Moderator

Apr 27, 2012, 7:25 PM

Post #12 of 12 (11500 views)
  post locked   Re: '96 Ford Explorer; rough idle  

This is an old thread - please start your own with your own specifics,


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