Hesitation, Rough Idle, CEL - please help!

[jwelburn]

Hi, My buddy has a 99 Ford Explorer with the pushrod 4.0. Last week, the check engine light came on with the Cylinder 4 misfire code. The car wouldn't idle worth crap and hesitated severely under load.

We took a peak at the spark plug, which looked just fine (it supposedly has just been tuned-up). A friend of mine has a 99 escort with the same type of spark plug wires, so I popped one of those on there and reset the code. The owner drove it around for a few days and said all the problems went away.

About 3 days ago, the CEL came on again. This time, it listed the Cylinder 4 misfire along with code p0174-Bank 2 System too lean. Now, we checked the connection on the new 'autozone special' spark plug wire and it was still good. From reading on this site, I noticed that the MAF gets dirty at times and will throw the P0174 code. So, I bought some electrical cleaner and sprayed off both that and the IAC, along with the coil-side connection for the #4 spark plug wire.

Now, somewhere in my infinite wisdom, I managed to lock the keys in the car while it was running. Since the hood was up, I decided it would be easiest just to pull each spark plug wire from the coil and drop each cylinder until the car died. The usual happened when I did this (rpm dropped, etc). However, when I pulled the #4 spark plug wire, I couldn't hear any change in the idle at all! So I'm still thinking that the problem with the misfire isn't solved...

All the symptoms still persist after cleaning the sensors and changing the wire. Rough idle is still present (shaking, etc). The car still hesistates under load and takes practically full throttle for it to accelerate. I'm pretty sure I can hear it missing, but can't tell for sure. My experience with fords lies only in 302s, so I don't have much of a baseline for the explorer. Plus, the owner isn't mechanically inclined, so he can't really explain how the car 'used to be'.

Any suggestions about what to check next?

I figure maybe the coil pack has gone bad, but I wouldn't think that would throw the p0174 code. If the car really did have a tune-up, I would expect the fuel filter to have been changed too. Maybe a fuel injector? Mulitiple problems at once?

Thanks for your guys help.

Jeremy

 

[marragtop]

Sounds like you already replaced the wire, so you can eliminate that. I know you said the plug looks OK, but I'd replace it or switch it with another to see if there is any difference. If you still have a dead # 4, consider the coil pack.

 

[410Fortune]

the 02 code is likely a result of the dead cyl on that side.....
Something is a miss hahaha no pun intended.

Dont re-use escort plugs, replace the plug int he cyl if not all 6 at the least!

 

[jwelburn]

Thread Moved

Sorry about the thread being in the wrong spot. It's just a crisis on my part because the owner is supposed to be leaving tomorrow afternoon for a 800 mile trip, and the possibility of it running lean (and the risk of blowing up the engine that comes with it) makes it imperative that something gets fixed. I'm just running low on ideas about what to do next, and don't want to have to take the thing into a shop so the owner can get worked over.

Thanks for suggestions, I'll double check everything tonight and look again for any possible vacuum leaks. I'll also pick up another spark plug for the #4 cylinder and see if anything improves.

Will update with results as they come in. Thanks

-jeremy

 

[jwelburn]

Well, took the coil pack into Autozone. Turns out that two of the primary circuits are out of spec in resistance. Also, a 2nd look at the #4 spark plug showed a stark contrast (blackened, etc) in comparison to the #4 and #6 plugs (which looked just fine).

My plans are to get a new coil pack, new #4 plug, and run some LUCAS fuel cleaner through the system. Hopefully that'll stop whatever problems may be around.

Thanks again for your guys help

 

[jwelburn]

Finally got some work done

Got the coil pack and new #4 spark plug installed today. Also filled the tank up with gas and mixed in some Lucas injector cleaner.

However, the car still sounds like it has a miss and lacks power. No codes were thrown yet, but I'm doubtful the situation has been solved. Any other suggestions on what to do/check/waste money on??

-Jeremy

 

[410Fortune]

replace all 6 plugs, not 1
Did you reset the battery after replacing parts?
Check the wiring to the coil pakc and firing order
Clean the MAS

reset the battery and try again.

 

[Tony H]

I would have guessed the new Pack and new plug would have worked. Plugs that get loaded up from missfire do go to toast easily and wont fire. Happens all the time on Old motorcycles with gummed up Carburetors.
Have you looked at the harness going to the Pack? maybe a pin is bent/missing/ corroded.

 

[jwelburn]

Sorry about the delay in reply. Hopefully this will help someone in future reference.

All it needed was another half hour for the computer to readjust itself. When I started it up after letting it sit, the thing idled/ran just fine. In fact, my buddy (the owner) says its never run this good since he's had it.

The new plug and coil pack was the solution. I've also been running some Lucas cleaner and seafoam through it as well, which is probably helping with mileage and power.

Thanks for your guys help on this one.

-jeremy

 

[csmicfool]

I'm having a similar problem- I am getting no spark codes for cyl 3. (4.0 OHV) I just checked all the plugs and wires. The only thing I found out of sorts was a wire in the loom for the coil-pack harness. It doesn't go to the coil, but to a disconnect and a "ground?" The "ground" looks like a relay with a single wire comming out one end and a piece of flat metal comming out the other side (small eyelet and gouges from a previously installed lock nut). The "ground" is hanging loose- I dont know what it's for or what it's supposed to be fastened to.

HELP!!!

 

[zpexploder]

I am having bad idle and hesitation.

I have cleaned MAS, IAC, new fuel filter, air filter, run Sea Foam through vacuum sprayed a li'l WD40 in EGR valve and still having rough idle and hesitation in the form of surging when on open road. Have not yet changed plugs, wires or cap and rotor. Any ideas? Goin crazy!

Thanks.

 

[ThePhoenix]

change the plugs, wires or cap and rotor.....I had idle issues and did that (as well as fuel filter) and it was fine after that!