My '94 Explorer Limited (195K + miles) has a major driveability problem.

The back story: A couple weeks ago, I come out of work and start my Explorer up. It idled pretty rough and felt like one cylinder was missing, I made it the 8 miles home with the check engine light coming on peroidically and it stalled out just as I pulled into my driveway. I suspected the coil pack was failing so I checked it with a resistance test. The resistance was slightly out of spec so I replaced it with a used one that was within spec. I also went ahead and replaced the air filter and fuel filter. It started right up and ran perfect, until the next day when it barely started and sputtered worse than ever.

It is completely unpredictible, sometimes it starts right up and run smooth. Other times, it barely starts and runs terrible or doesn't start at all. Next I purchased a fuel pressure tester and tested it while it wouldn't start and got 38 psi. Then I did a KOEO test with a code reader and got a 565 Cannister Purge (CANP) solenoid-circuit failure. I am pretty sure this fault is not what is causing the Explorer to not start or sputter this bad. I have inspected the whole engine for loose connections and cracked hoses. I checked the compression on one of the cylinders and got 120 psi (I doubt this would be a problem due to the fact that it runs perfect some of the time.)

I am completely stumped at this point. I am open to any suggestions, thanks.

 

Could be an electrical issue..for example mine was doing something similar just recently.. the heat shield around the spark plug on my #7 cylinder made a few small cuts in the boot around the spark plug, causing it to arc out on the heat shield.. Mine did stall once.. Idled rough as heck.. at low rpm's and under slight load the problem seemed to worsen.. I did the same series of tests.. compression,fuel pressure,coil packs all checked out fine.. it was off and on for a few weeks before we figured it out.. and i had just had the spark plugs and wires changed a few thousand miles before.

Not sure if this will help but it never hurts to try some fresh plugs and wires.. sometimes it just turns out to be the simplest of things!

If you have a chiltons or haynes manual go through the routine maintenance section or read in the front where you can look up your symptom and it gives your suggestions of things to check for.. start with the simple and most inexpensive things and work you way up!

Best of luck to you!

 

Thanks, maybe I will just go ahead and try new plugs and wires. Money is tight for me and I was trying to avoid throwing parts at it, but I am getting very frusterated.

I do have the Haynes manual and have gone through the suggestions already. Someone else said to use a stethoscope and a noid light to check the fuel injectors, which I will try as well.

Thanks for the response.

 

Well I think I narrowed the possibilities down a bit. I used an ignition tester to check for spark on each plug wire (all checked out good). I then pulled all the spark plugs and checked them each by plugging them into a plug wire on my other vehicle and starting it (they all also worked perfectly).

I am now convinced my problem is not in the ignition system. I have also noticed a lot of smoke and black soot out of the tailpipe when the Explorer actually starts and runs. From what I understand, this would indicate a very rich condition. I tried to use a screwdriver as a stethoscope to listen for the clicking of the fuel injectors (thinking maybe one or more of them is stuck open), however I was only able to get to two of them without removing the upper intake (both were working). Otherwise, it has to be something telling the computer to dump more fuel into the engine.

What do you guys think?

 

Time to put a guage on the fuel rail, suspect your FPR is dead, or the vacuam hose has blown off.

 

agree with the above

 

I will do it again, but I already put a gauge on the fuel rail and got 38 psi with the FPR vacuum hose connected. At the time I did this, the Explorer wouldn't start at all.

 

I rechecked the fuel pressure yesterday during a stint when the Explorer was running smooth. I got 30 psi with the vacuum connected, and 40 psi with the vacuum removed on the FPR. There was also no sign of gas leaking out of the FPR when I pulled the vacuum hose off.

 

possible failing MAP/MAF sensor?

 

I was thinking possibly the AIC (Air Idle Control) Valve.. this would cause your vehicle to stall when you take pressure off of the accelerator pedal and cause it to run rough ad idle or misfire.. but if it's causing midrange rpm or acceleration problems this likely isn't your cause. Also i don't believe the AIC can be electronically tested unless they make a special tool for that.

 

Is there a way I can test either of these? I just can't afford to throw more parts at it without having good probable cause.

 

Yeah, I doubt this is the problem since when it is running crappy, it does so throughout the RPM range.

 

You can unplug them, and the truck should still run. A faulty MAP/MAF can cause an engine to run worse then if they were unplugged. The computer compensates by calculating the proper fuel mixture from throttle position, engine RPM and coolant temperature

 

Ironically, I tried this just before you posted it. I unplugged the MAF while it was running lousy and it did run better. I then used voltmeter tests shown in the Haynes manual to confirm that the MAF was malfunctioning. I later started the Explorer again and it was running good with the MAF plugged in. I did the same voltmeter tests again, and the numbers were within specs. I am pretty sure the MAF is failing intermittently and causing my problem. It is just odd that the failing MAF never threw a code.

I plan to pick up a used MAF from the local salvage yard tomorrow.

 

Ryno if i may suggest.. I picked up some parts from a store before and connected them just to check.. and if that wasn't my problem i made sure and wiped off the dielectric grease or w/e and then returned it.. worked for me and i got all my money back..

Sumthing came to mind just now.. i was having sum problems where my X was running like crap and idled terribly rough... ran bad throught the rpm range but especially during accelerating from a dead stop and during low rpm's.. but it turned out i had a leaking exhaust manifold.. I hadn't noticed much noise from it until i crawled under and got closer to the problem.. Not sure if this is anywhere near your situation BUT..

Try getting a long piece of tubing and take it around all of the hoses and exhaust or vacuum areas to see if u can pinpoint anything.. its just a few dollars in hosing and may help if you can find sumthing.. Have you checked the pcv valve? usually located near or on your intake manifold or on/near the vacuum lines leading into the intake manifold.. remove it and give it a few shakes to see if it rattles.. if not its clogged..

Just throwing some ideas out there..