1998 Ford Explorer Idle Problems

I have a 1998 Ford Explorer with about 115k miles on it.
Four days ago, when the car was at idle, it started studdering. It usually idles at around 800RPM, but every five seconds or so it would go down to 400RPM and mildly shake the car. It has gotten progressively worse since then to the point where it studders every second or so. It only seems to do it when at idle, and if I am sitting at a stoplight (for example) it sometimes hesitates when I start accelerating. Once I am moving, there don't seem to be any problems. It doesn't seem to be directly connected to the engine being cold, as it still does this once I have been driving for a bit.

Anyone have any ideas? Two fillups ago I added some fuel injector cleaner, if that even matters. This will be only the second problem I have ever had with this vehicle.. The only other things I have had to do with it was replace the idle air control valve and thermostat. (50k miles ago)

Thanks!

Have you ever had a tune-up? I replaced the spark plugs, wires, and filters on my 1998 OHC 4.0l at 100,000 miles and it did make a difference in the idle and fuel economy.

Have you had to add any coolant? I have a tiny intermitant intake gasket leak on mine. I can go for months without noticing lower levels. Then that idle shudder starts on #4. Sometimes in less than 4K. If you pull the plugs, look for a little extra coating on one plug.

I am going to try both of your suggestions - I do admit that I have never changed the spark plugs/wires (and at 115k miles I probably should). Tomorrow I am changing them out tomorrow (along with the fuel filter). Thanks for the tip of checking for residue on one of the plugs.. I'll let you know how it turns out!

I did notice just recently that my radiator resevoir tank was empty - I filled it up and its lower again. That just might be the problem..

Another thing - It seems to be getting worse day by day - It is now studdering a tad bit while driving at lower speeds.. Not really noticable at higher ones (yet). :banghead:

Have you ever had a tune-up? I replaced the spark plugs, wires, and filters on my 1998 OHC 4.0l at 100,000 miles and it did make a difference in the idle and fuel economy.

Any trick to pulling the wires off the spark plugs? I tried w/ all my might and can't get the sucker to pull off.. It will click a little bit like its trying, but otherwise I'm unable to get it off.

While gripping the rubber boot of the plug, pull and twist at the same time and the plug wire should come loose. There is nothing special attaching the plug wire to the plug, so it should eventually pull loose. After 115k, the rubber is probably adhering to the plug and creating a vacuum, so that is where the twisting should help.

Whatever you do, don't pull on the wire because the carbon fibers ,located insigde the wire, can be easily damaged.

Good luck!

Mark Keehn

BTW on my 4.0 SOHC, the rear plug on the passenger side was the most difficult to reach.

I have a 1998 Ford Explorer with about 115k miles on it.
Four days ago, when the car was at idle, it started studdering. It usually idles at around 800RPM, but every five seconds or so it would go down to 400RPM and mildly shake the car. It has gotten progressively worse since then to the point where it studders every second or so. It only seems to do it when at idle, and if I am sitting at a stoplight (for example) it sometimes hesitates when I start accelerating. Once I am moving, there don't seem to be any problems. It doesn't seem to be directly connected to the engine being cold, as it still does this once I have been driving for a bit.

Anyone have any ideas? Two fillups ago I added some fuel injector cleaner, if that even matters. This will be only the second problem I have ever had with this vehicle.. The only other things I have had to do with it was replace the idle air control valve and thermostat. (50k miles ago)

Thanks!

Check your oil filler cap for any gunk in it. SImilar symptoms to mine. Both heads have now failed, approximately 1000Km apart. The first was replaced, with teh second being tested, and passing. It then failed virtually straight away.

Hope it ain't what I got.

Greetings all,
Hope all of you and your love ones are doing well. I need the location of the IDLE SPEED MOTOR, having probs finding it. Thanks

While gripping the rubber boot of the plug, pull and twist at the same time and the plug wire should come loose. There is nothing special attaching the plug wire to the plug, so it should eventually pull loose. After 115k, the rubber is probably adhering to the plug and creating a vacuum, so that is where the twisting should help.

Whatever you do, don't pull on the wire because the carbon fibers ,located insigde the wire, can be easily damaged.

Good luck!

Mark Keehn

BTW on my 4.0 SOHC, the rear plug on the passenger side was the most difficult to reach.

Sorry it took me so long to reply. Took a while to get a friend over and help me out w/ the switchout. We replaced both the spark plugs and wires. The wires took a very strong police officer 4 hours to completely pull off. We had to cut some of them and then use a wrench to pull the pieces off. (perhaps there was a better way, but those suckers were so stuck on, we couldn't figure one out). After then switching out the plugs and putting the new wires in (although we couldn't use the original path of the wires, because of the tight fit), the engine runs 100 times better! The idle problem is gone. Thanks a lot for your help!!