'97 SOHC intermittent stutter/bad idle

[97xlt4.0]

Okay, I searched, and didn't find anything that quite matches my problem....although if I missed a thread, I apologize!!

I've got a '97 SOHC with 182k on it. Up until recently it's been running really well. Still does, mostly. Over the last 2 weeks, I've been having an intermittent idle/hesitation problem. What I mean is, that I will be sitting at a stop, and can feel the idle going up and down, in addition to watching it on the tach....usually, tapping the gas will make it go away. Also, when taking off from a stop when this happens, there's a noticeable stutter when you press the gas pedal, and then it picks up and goes fine.

Also, there has, so far, been no CEL lit. Can there still be stored codes(I'm looking at buying a Scantool, or a code reader of some kind)?

I bought the Explorer used last year, so I don't have a the best idea of what sensors have been replaced, etc. I replaced the MAF last week, and the IAC over the summer. I also put new spark plugs in in September.

Sorry for the novel, and any ideas are appreciated!!!

 

[97xlt4.0]

UPDATE- It's now doing it cold OR warm. When I was driving earlier, there was an audible clicking noise that corresponded with the stumbling idle. Still no CEL lit....

Any help would be great....really really short on spare time, so if i cant get it figured I'll have to take it in....

 

[FastIndy]

Does your idle alternate, dropping low for a couple of seconds then back up to normal?

 

[97xlt4.0]

yeah, thats exactly it!! shakes, idle drops, and repeats....then hesitates when you hit the gas to go....

 

[FastIndy]

Well then the good news is you have company I've got a '97 Ex SOHC that does the same thing. At a stop, the idle will drop down to about 500RPM, the engine will shake, then back up to 800-900. At anything except for a stop, the engine behaves normally.

I, however, got a code indicating the IAT circuit was faulty...Put in a new IAT sensor, cleared the codes, and about 30 minutes later got the code back. Maybe something wrong with the wiring, unless I'm missing something.

 

[97xlt4.0]

good to know mines not the only one having fits!! lol.

So far I haven't thrown a code....thought it was going to tonight on the way home, though!! What really got me was earlier when I was driving, and there was a 'click' noise going with the problem(it would click, idle goes down, click again, idle goes back up...)
I'm leaning towards it being a sensor issue of some kind, but who knows....

 

[2000StreetRod]

A/C compressor cycling?

Is it possible your A/C compressor is cycling on and off? The A/C is utilized when the inlet air temperature is above 50 degrees F and your heating/AC control is in defrost, upper/lower and AC. The PCM adjusts the idle speed when the A/C compressor is engaged/disengaged.

 

[97xlt4.0]

Yes, I do believe the A/C compressor has been cycling on and off a LOT lately. Hasn't been until the last week, roughly, that this idle issue has shown itself.....

I'm going to go after the throttle body today and clean it(it's pretty black!!), as a start....

 

[jremington59]

You also want to look at the idle air control. Try cleaning it and see if that helps the idling.

 

[97xlt4.0]

I wish I had kept the original IAC I pulled off over the summer....that way I could swap it back on for testing!! I have some throttle body and MAF sensor cleaner....should work for the IAC too, right??

Thanks for the ideas so far, I have some things to start with now!!

 

[97xlt4.0]

UPDATE- I had the codes checked(at Autozone...since I dont have a reader yet), and there were no codes at all showing. It's been running fine this morning, but I still plan to clean the throttle body this afternoon and test the IAC(picked up a new one just in case)

-Mike

 

[97xlt4.0]

Okay, I cleaned the TB.....it was FILTHY....oil caked up on the back(I removed it and gave it a good cleaning), seems to be running okay. I did notice oil in the intake though(not puddled up, but it just looked not right to me?)

Anyways, I'll have to drive it this week to school and back, and to the airport saturday morning, so we'll see if the stuff I did today helped....

 

[FastIndy]

Update?

 

[97xlt4.0]

Well...not much of an update, but here's where I'm at:

Replaced MAF and IAC, removed and cleaned throttle body, and reinstalled. It still comes and goes.

I did notice when I took the TB off that the throttle cable has a noticeable amount of slack in it...lol!! So, I'm thinking the throttle cable mod is in my near future.

I'm also thinking of buying a code reader....i had AutoZone check them, and they couldn't find any, but I'd like to see for myself. Since I'm a student right now, I get discount with Matco and Snap-On, so I figure now's the time;-)

Any new ideas on this issue would be great....I was wondering if the TPS might be slowly going bad, but still learning how many of the sensors work!!

 

[xFatcatx]

I know this thread is old but any chance you figured out the issue? I have a 99' Sport 4.0 SOHC with the same exact symptoms. So far I have cleaned the IAC twice, cleaned MAF, and changed upper/lower intake gaskets and new air filter.

I am planning on cleaning tb, doing plugs/wires, and since I am pulling the intake again (to torque to spec since I didnt the first time) mine as well throw a new thermo in there, and new pcv valve. Cel threw code P301 which after some research appears it could be a million different issues......

I located the PCV valve and read that it cracking, or a crack in the bend could be a vaccum leak but without the intake off I cant see anything or understand where a crack could be. When I put my finger on top of the PCV valve it does seem very loose and wiggles a bit, anyone know if this is normal?

I hate to just start throwing money and parts at this but dont see where I have a choice. Tags are up this month to and I am weary it will pass emission with the idle issue.

 

[FastIndy]

I know this thread is old but any chance you figured out the issue? I have a 99' Sport 4.0 SOHC with the same exact symptoms. So far I have cleaned the IAC twice, cleaned MAF, and changed upper/lower intake gaskets and new air filter.

I am planning on cleaning tb, doing plugs/wires, and since I am pulling the intake again (to torque to spec since I didnt the first time) mine as well throw a new thermo in there, and new pcv valve. Cel threw code P301 which after some research appears it could be a million different issues......

I located the PCV valve and read that it cracking, or a crack in the bend could be a vaccum leak but without the intake off I cant see anything or understand where a crack could be. When I put my finger on top of the PCV valve it does seem very loose and wiggles a bit, anyone know if this is normal?

I hate to just start throwing money and parts at this but dont see where I have a choice. Tags are up this month to and I am weary it will pass emission with the idle issue.

I did in fact figure out my issue at least. The wiring harness had come loose from a tie-down and was rubbing on the belt. It looks like the harness has about a foot of extra length which is secured with black tape to a plastic clip under the alternator. It had severed some of the wires, and melted some together. So you may want to follow the IAT/MAF harness back as far as you can. I changed out those sensors and looked for a wiring problem and still didn't notice for a long time!

 

[xFatcatx]

Thanks I will check that out also.

 

[xFatcatx]

Well it passed DEQ (emissions) here in Oregon so that is good. Not sure if that would give any insight to the issue. Doing the tune up Saturday so I will update after that.