Idle problem - 1998 Explorer V6 SOHC Eddie Bauer

So I inherited my future father-in-laws Explorer (it was his pride and joy but he was ready to retire it so he passed it on to me to keep me out of a car payment).

It's got 122,000 on the odometer, but has been very well maintained by him so that's a plus. As with any car that is 10 years/120k miles it has had a few issues.....In the past few months since I got it, I've fixed a sway bar, rear axle leak, belt tensioner, thermostat and now a IAC.

The last two items were a result of the cooler weather coming around again this time of the year in Chicago, but I'm still a little miffed. My temp gauge never rose 'hotter' than 25% and the thermostat fixed that. The IAC was replaced because of my large issue - the one that still exists.

------ON TO THE PROBLEM----------
After the engine is warm, the idle will 'pulse'. It idles normally around 700rpm steadily/smoothly, but as of lately it will spike as high as 1,000 and as low as 500. My local shop (who replaced all of the above listed parts) have the new IAC 'on loan' to me as they're not positive it's the problem - and I'm pretty sure of that now too. The original IAC apparently was inspected and seemed okay, but was swapped anyhow to make sure it wasn't the problem. They did pull a code from the car (don't have it handy) but it was that it was running rich. The exhaust is VERY nausiating/smells like gas.

With the IAC obviously not the problem. What do I look for next? As I mentioned, the car was inherited so it's nothing I want to just start dumping cash into. The shop mentioned they would go after the plugs/wires next if the IAC didn't fix the problem. The plugs have been on the car for 44,000 and the wires are the originals.

Any suggestions?? Thanks everyone.

The oxygen sensors are your problem. First ask the previous owner if they have ever been replaced. I can almost guarrantee thats whats doing the surging. I too had that same problem from my 97 I just bought, EVERYTHING on the dang truck was Motorcraft, the previous owner(female) DID nothing to it but get oil changed every three months. I went Bosch Platinum 4 plugs, Bosch wires, new thermostat( wasnt getting heat inside) and K&N filter...IT SURGED still...replaced both 02 sensors and viola! Smooth as silk and about 24 MPG.

First, check for any signs of a vacuum leak. Supposedly the PCV hose is a common culprit, but I can't tell you where.... Never had the issue myself.

The other (and most common culprit) is the lower intake manifold gaskets. There is a service bulletin that covers the replacement of those along with the driver's side cam chain tensioner and the oil gallery volume reduction plug. It's the 00M12 service kit which any dealer should have on the shelf for around $40, and should take a few hours to install (provided you have a 1-1/16" combination wrench at your disposal).

Search for 00M12 on the site... it comes up a lot this time of year as the cool weather sets in.

Good luck!

My 96 had the same issue, however, all i did was take a can of throttle body cleaner and sprayed the Mass air flow Sensor to clean it. There is a wire in there that will be red if clean. I put the air filter and mass air floe back on and it fired up and remained cleaned. I then cleaned the Idle Air Control and removed the snorcole tube and cleaned the butter fly and intake before i put the cleaner away, I was surprised with the amount of carbon and dirt around the inside of the intake/butterfly.

hope this mess of info helps..

to much coffee and lack of sleep..

got a fix!

Well, I got a fix. My shop had put on a new IAC as a try to get it fixed. It still showed the same issue so the new IAC was replaced with the original. They scanned again and pulled off the same 'lean' code as well as did some other trouble shooting. They recommended I replace the 40K old plugs and the 120K plug wires as well as replace the MAF. They gave cleaning the MAF a shot with no luck.

So, I did all the work myself. Replaced the plugs and wires. Engine ran better, strong acceleration. It helped the problem, but I still wasn't satisfied. I then shopped around for MAF sensors, replaced it (in all of 10 minutes) and we have a fix.

so, CULPRIT: MAF sensor. $114 at NAPA with core trade-in
Plugs and wires helped and were much needed anyhow.

stoke21 said:

Well, I got a fix. My shop had put on a new IAC as a try to get it fixed. It still showed the same issue so the new IAC was replaced with the original. They scanned again and pulled off the same 'lean' code as well as did some other trouble shooting. They recommended I replace the 40K old plugs and the 120K plug wires as well as replace the MAF. They gave cleaning the MAF a shot with no luck.

So, I did all the work myself. Replaced the plugs and wires. Engine ran better, strong acceleration. It helped the problem, but I still wasn't satisfied. I then shopped around for MAF sensors, replaced it (in all of 10 minutes) and we have a fix.

so, CULPRIT: MAF sensor. $114 at NAPA with core trade-in
Plugs and wires helped and were much needed anyhow.

Click to expand...

i guess i lucked out with the cleaning. Be sure the wires are not touching anything. i had mine replaced and then the truck drove like crap after 30k would backfire on the highway and gas millage was poor, I found that a wire was rubbing on a heat sheld and wore through shorting out, its common over site mainly on the front drivers cylinder. Just a heads up.

premature reaction?

Well, as much as it pains me to repost because the problem is still there....it's the truth.

While it's no where near the severity it used to be, the engine is still 'stumbling' a bit when idling from time to time and I'm get the CEL very frequently.

Has anyone replaced an O2 sensor and had it be the proper fix without actually getting an 02 sensor code? I'm really thinking it's a sensor/small part issue. No drive'ability or starting issues, strictly idling.

Help (again)?

Could possibly be your tps...

A lean condition is normally an intake leak. AND your 4.0 is prone to have the lower intake gaskets leak. I'd pull the whole intake off and put new gaskets on it. Pertty easy to do, just takes a bit of time. Your lean condition should go away, along with a much stabler idle at all times.

gijoecam said:

First, check for any signs of a vacuum leak. Supposedly the PCV hose is a common culprit, but I can't tell you where.... Never had the issue myself.

The other (and most common culprit) is the lower intake manifold gaskets. There is a service bulletin that covers the replacement of those along with the driver's side cam chain tensioner and the oil gallery volume reduction plug. It's the 00M12 service kit which any dealer should have on the shelf for around $40, and should take a few hours to install (provided you have a 1-1/16" combination wrench at your disposal).

Search for 00M12 on the site... it comes up a lot this time of year as the cool weather sets in.

Good luck!

Click to expand...

my98nnj said:

A lean condition is normally an intake leak. AND your 4.0 is prone to have the lower intake gaskets leak. I'd pull the whole intake off and put new gaskets on it. Pertty easy to do, just takes a bit of time. Your lean condition should go away, along with a much stabler idle at all times.

Click to expand...

Use a can of starting fluid to pinpoint the vacuum leak. My money is still on the lower intake manifold gaskets.

-Joe

gijoecam said:

Use a can of starting fluid to pinpoint the vacuum leak. My money is still on the lower intake manifold gaskets.

-Joe

Click to expand...

thats a good idea. I use to use a can of propane and the torch that i would use for plumbing. NOT IGNITED, vacume leak would suck the propane in and raise the rpms. same effect as the starter fluid

cheers.

timn8er said:

thats a good idea. I use to use a can of propane and the torch that i would use for plumbing. NOT IGNITED, vacume leak would suck the propane in and raise the rpms. same effect as the starter fluid

cheers.

Click to expand...

That's a handy way to do it... never thought of that!! Good call!

-Joe

UPPER GASKET:
Am I crazy to consider doing this job myself? I'm no mechanic, but have no problem changing oil, plugs/wires, cold air intake (different car), o2 sensors......

I'm very mechanically inclined, just a little hesitant to open the top half of the motor up. I understand what's broken and what needs to be fixed, just don't want to open up anything that I'm going to mess up big time and be stuck with a car that won't run.

all you do is remove and replace, keep track of all bolts and take your time, don't make it more complicated than it is. For encouragement, call the shop and ask them what it would cost if they do it.

It's not terribly difficult, and there are several useful threads on this forum showing exactly how to do it. Now that I've done mine, I could do it again in about an hour... It really is a piece of cake.

-Joe

stroke21 im having the same problem and then some. like my98 said put on both sets of new intake gaskets, and while you've got your intake off put in a new ECT(Engine Temperature Control sensor. its the sensor right behind the thermostat) its usually hard to reach and causes lean/idle problems. and like team and gijoecam essentially said "it sounds harder than it really is"

similar issue

I have a similar low idle when warm/hot situation with my 98 OHV.

I have replaced the spark plugs and IAC, cleaned MAF, traced vac lines, and reset computer. Fuel and air filters are only a few months old. Minimal help.

Idle will get as low as 500 but will not stall out then will surge to maybe 700-800 then drop, then surge, on a 30 sec cycle or so. Park idle is fine. The cold drive idle is fine. No CEL present.

This coming weekend I will replace the spark wires (due anyway) and will use some tbody cleaner spray to see if the intake gaskets are leaking. If it's a minor leak you (and me) might be able to get away with tightening up the bolts.

ok which 2 sensors im looking they got upstream downstram right and left im confused now

Check your hoses coming off the back of the intake manifold that go to the "t" then down to the PVC valve... I had same issue in my 97 sohc and one of the hoses was torn in one part and collapsed in another part the hoses are a much easier fix (if that is indeed the problem) than the intake manifold. However if you do undertake the job of the intake, I highly suggest getting the Haynes manual and be sure to follow the proper torque order upon reassembly. And remember to note that you will be torquing in INCH POUNDS, NOT FOOT POUNDS, don't wanna crack or worse shatter that high quality ford plastic. Lol... Sheesh, u think u gotta intake leak now.........