'94 explorer that has serious idle issues

[Wormy]

Hello, I have a '94 that has random idle issues. It is becoming less of a pain and now more of a danger. It will idle normally around 750 and sounds like a misfire occasionally and then idle will rev. I've done the tune up, plugs, wires, fuel filter and etc. Cleaned the IAC, MAF and throttle body. Replaced the IAC and MAF since several people told me that it had to be it, condition is worse with new IAC. Replaced FPR due to small leak into vacuum. Checked for leaks in airbox to throttle body duct. Fuel pressure was in spec, not varying tremendously. Vacuum is stable at 20 until the misfire then will increase to 22 before dipping quickly to 17 when the engine revs. No CEL, No stored codes. Reset the computer multiple times. Had it ran on a scanner at local garage, it didn't detect any abnormals. Running high octane fuel.
Saturday it put me in the field in reverse backing out of the garage. We had a decent little snow and I was heading to work, backed out and was waiting for the door to go down when it revved up and sent me sliding out into the field. Today it just about put itself through the front of the garage when my wife came home. When she was rolling it was running at 3k rpms, when she was trying to stop it was running at 1.5K rpms and still pushing. I am getting to my last straws on this car.

 

[Verno]

Have you tested your TPS?

 

[Wormy]

Yes, I checked it's voltage at base idle and through the sweep to full throttle position (Key on engine not running). Did not see any abnormal jumps as I moved it.

 

[Wormy]

By the way, when I checked the TPS, I went ahead and did a base idle calibration like was suggested on another site. I turned the stop screw out until I had 0.010" clearance and then turned it in 1 1/2 turns. Checked the TPS voltage and it had 0.94 volts on it at throttle closed/idle. It actually seemed to run well after this for a day but then became ugly with a vengence.
Going back, it seemed strange that when I replaced the IAC it went wild. That was before I had done the base idle. I thought I had a bad IAC so I made the parts store swap it. It didn't do any better. The original IAC wasn't causing erratic idle, it was causing low idle condition until I cleaned it out.
On a side note, I was searching the site and noticed a link about the CMP making noise. I have chased a phantom squeak for sometime on this vehicle and have never found it. After hearing the you tube video, it sounds much like this vehicles squeak. My question is do you guys think that there could be something in the CMP causing the issues I am having with misfire and idle search? This has been a great running vehicle up until now. 236,000 miles and I havn't done anything but standard service changing lube in differentials and transmission, standard oil change etc. I've been through the shocks, brakes, bushings and such but the motor and tranny are factory; never cracked the seal on any of it.

 

[Wormy]

OK, I have checked all the connections and cleaned / resealed them. This didn't do anything for it. I mentioned the CMP. I can't find a CMP on this vehicle and can't even find one listed online for it. So maybe that was the wrong tree to bark up! Last night it would bounce between idling around 750rpm and then ramp up to 2200 to 2300 rpm and no one was even near the vehicle. Any further ideals? Some have suggested changing the PCM or the ignition control box. I'm not normally into shotgunning parts but it is getting to the point I have way to many hours invested in this ride.

 

[Wormy]

Now really concerned as to where to go on this ride. Friday night my wife came in late very frustrated and upset at the vehicle. It was idling at 3000 RPM when in park or neutral. I ended up having to take it out that night and it was pushing hard especially on some of the old back roads we have around here. I got back in shortly after 1:00 AM and was thinking as I was headed down our road of things I wanted to check and the blasted thing dropped down to idle just fine and would not act up. Maybe forty dollars for the TPS will be my next step. It's either that or my wife my start a target practice session with this thing!!

 

[nexis]

just a thought, check the fuel pressure regulator vacuum line for gas, because you may be pulling fuel in there which could cause the problems.

 

[Wormy]

Thanks for the suggestion, I did check the line for fuel. It didn't seem to have any but the fittings were a bit spongy so I opted to swap a new one in. Not a bit of change. Replaced the tps also and it didn't do a bit of good for me.

I think my wife might be loading the gun?? Hope it's aimed at the car and not me!!

(Just kidding, she loves the car!)

 

[33exploder]

SWAP the fuel pump relay with any other relay if it fits the issue unload the shotgun and buy a new relay

 

[nexis]

I doubt it would be a fuel pump relay, but thats a free check, so might as well. As far as the computer location, its behind the dash, you have to pull the dash to get access to it. Upper passenger side, pretty much right behind where the shelf is in the dash.

Something else to try, have you checked your EGR valve? Start the engine cold, let it idle a few min, and put your hand on the EGR, if its hot, its bad.

 

[siTTinLo420]

hello,, i dont know if you're still having high idle issues, but i have had the same issues with my 94 explorer before,,and thought by replacing everything i would correct the problem,,, but when i resolved my issues,, it was done by un-doing every ground connection i could find and sanding them clean and re-connecting them,

, and i strongly suggest looking into your cooling system,,, if the ect sensor isnt working properly,,that will throw the idle all out of whack,,so check your coolant and "BURP" the system,,, these are things you can try,,that wont cost any more money,, but in my past expierience,, theses 2 little things can make a huge difference,,,

a while back,when i'd first start my explorer,, it would rev to 2000 rpms than come back down slowly,,, way too high for my taste,,,, but it did this for weeks ,till one day i decided to check my coolant,, the engine temp was already warm,, and when i opened the radiator cap,,, i heard a "gurgleing" sound like air bubbles in my motor?? but since than my idle is back to normal..

but give these things a try,,, it might work,, if not,,at least youre not out any money,,and you know all your ground connections are clean and your cooling system is good to go,,,

 

[Wormy]

Issues has been resolved!!!

OK.... in regards to the relay, I actually replace all 6 in the relay box every other year religiously. It eliminated a lot of issues so that is now a standard preventative maintenance item. As for the FPR, it had been replaced already and the egr was checked also. I did remove the ignition control module due to there was a service bulletin about it's ground connection and also cleaned every connector and resealed with no benefit.
The fix was the computer, I couldn't find a match local so I went to the Ford dealer and let them check it out. Ends up the processor was running slow, it wouldn't register feedback on time, it would register faults if you disconnected the MAF, ECT or any other sensors. When it would try to tune and adjust, the system wouldn't register faults, it just couldn't keep up with the feedback it was registering. As of now, it has ran for two weeks without issues!

 

[shaggymane]

Just wanna say thanks for coming back and posting the outcome and adding to the body of knowledge. So many don't.

I've had the erratic idle too with no success from the usual fixes. But I've got a 5spd do it's easier to live with.

 

[truckguy]

Thanks for posting what the fix was, my ex has had a problem with the Idle for years and have had several other problems, more important. When it became a problem and started surging dangerously I just disconnected the IAC and ingored the problem. I recently had to replace the engine wire harness so reconnected, and idle didn't work at all until I drove to a lower elevation for a few days and then it worked except often too high and would slowly return to 750. When I returned home (4000') again no idle. I guess the pcm is next on the list.