Engine missing-Tried all I know, all out of answers!?!

[DontPanic]

I have a 2002 Ford Explorer Sport that started jerking/missing when I would go up a rise or hill about 2 months ago. Since then I've replaced the fuel filter (which was filthy but didn't solve the problem), changed air filter, replaced the spark plugs, cleaned the EGR valve, cleaned the throttle body, tested the fuel pressure and it was fine (about 30 psi). Any pointers? I'm pretty new to this so take it easy on me. My cousin plugged it up and couldn't get any code errors and the check engine light doesn't come on. When I pull the vacuum hose off the EGR valve there is little/no suction but when I removed the hose elsewhere (I'd have to look to tell you where) I was getting plenty of suction. It has gotten worse and worse. It cranks fine, idles a little rough but doesn't completely "die". I'm at a loss, any pointers would be appreciated.

 

[swshawaii]

Inspect the infamous PCV elbow, including the underside . GL

http://www.explorerforum.com/forums/showthread.php?t=314670

 

[Flash]

Then try spark plugs, leads and coil pack.

 

[Thomas_1]

I going thru the same problem too. I replaced the IAC valve and the ignition coil also cleaned the throttle body and still have the problem. I'm going to try the spark plug and wires next.

 

[RickOTR]

When was the last time you had the fuel injectors professionally cleaned...

 

[Runnin'OnEmpty]

I have a 2002 Ford Explorer Sport that started jerking/missing when I would go up a rise or hill about 2 months ago.......

That's a classic symptom of weak spark somewhere.
It could be a plug or wire with high resistance, or a
poor wire terminal connection. Might also be a section
of the coil pack getting weak.

You might try starting it up on a dark night and look
for arcing along the plug wires. If you're good with a
multimeter, you can test the resistance in the plugs,
wires, and coil until you find the specific trouble. Or
if you haven't the time or inclination, just replace the
plugs and wires with new ones. If that dosen't fix it,
then a new coil pack probably will.

 

[DontPanic]

Thanks everybody. I'm out of town (I'm driving wife's truck) and will inspect that elbow when I get home. @ Flash I replaced the plugs but not the wires. That's probably my next move. Rick, just used some "good" injector cleaner but just from parts store so injectors haven't been professionally cleaned since I've had it.

Runnin, sorry for having to ask this but how do I go about checking the coil pack with a multimeter? Thanks for your patience guys, my pops wasn't around to teach me alot of this stuff so just learning from my mistakes right now.

 

[DontPanic]

If it turns out to be bad plug wires or a bad coil pack would that explain the lack of suction on my vacuum hose? Thanks

 

[RickOTR]

I would look at replacing those SP wires before I would do anything else. The DIS coil rarely goes out. Try some CRC Guaranteed to Pass in the tank and follow the directions like it's the bible. This stuff really works, or at least it did for me as I had the same symptoms as yours. My X ran like new when I did. As for the vacuum at idle there shouldn't be any. There should only be vacuum when the EGR opens up and that's when it's at a certain load or RPM range

 

[Runnin'OnEmpty]

........
Runnin, sorry for having to ask this but how do I go about checking the coil pack with a multimeter?.......

Remove the connector plug and check the primary
resistance by connecting the probes to the positive (+)
terminal and each negative (-) terminal of the coil.
Resistance should be about .3 to 1.0 ohms, and the
resistance should be the same for each checked pair.

Then check the secondary resistance by probing the
paired companion cylinders (1-5, 2-6, 3-4). Resistance
should be about 6.5 to 11.5 K ohms. (Probe where the
plug wires connect to.)

Most resistor spark plugs will have about 5-8K ohms
measured from the tower terminal to the interior tip
(not the grounding terminal).

Resistor plug wires vary according to type, but most
have about 6-12K ohms per foot of wire.

It takes a little time and effort to do these checks, but
might save some money...

 

[apache437]

any way you can post a pic or two? i'm not getting where to poke what... i don't see labels on the plug so maybe wire colors, etc. Thanks

 

[drdoom]

Check the Haynes Manual.

 

[2000StreetRod]

low fuel pressure

I have a 2002 Ford Explorer Sport that started jerking/missing when I would go up a rise or hill about 2 months ago. Since then I've replaced the fuel filter (which was filthy but didn't solve the problem), changed air filter, replaced the spark plugs, cleaned the EGR valve, cleaned the throttle body, tested the fuel pressure and it was fine (about 30 psi). . .

Fuel pressure is not fine. 30 psi is less than half what the pressure should be. Mine runs about 65 psi at idle thru 5,000 rpm in Park. I seem to recall that your 2002 has an engine speed limiter (around 3,000 rpm) in Park or Neutral. Your fuel pressure should be at least 60 psi. I suspect that you have a weak fuel pump. I am convinced that delayed fuel filter changes results in early fuel pump failure.

 

[DontPanic]

2000, I will recheck myself on that but I think it was about 30-40 psi.

Fuel pressure is not fine. 30 psi is less than half what the pressure should be. Mine runs about 65 psi at idle thru 5,000 rpm in Park. I seem to recall that your 2002 has an engine speed limiter (around 3,000 rpm) in Park or Neutral. Your fuel pressure should be at least 60 psi. I suspect that you have a weak fuel pump. I am convinced that delayed fuel filter changes results in early fuel pump failure.

 

[ZebraT]

If it turns out to be bad plug wires or a bad coil pack would that explain the lack of suction on my vacuum hose? Thanks

Probably not, but a clogged exhaust system could explain a loss of vacumn. If it's REALLY clogged, it can also cause misfires.

 

[DontPanic]

Thanks Runnin on E and Rick...

Runnin and RickOTR, thanks for all your help and for the instruction on how to test those plugs.. The Sport is sitting while I'm out of town so I haven't laid eye son it since my last post. I have bought new plug wires but haven't tested plugs yet or replaced wires so I'll report back after I do and let you guys know if that addresses the problem. I wish I'd have discovered this website 4 years ago and it woulda saved me some change!

Remove the connector plug and check the primary
resistance by connecting the probes to the positive (+)
terminal and each negative (-) terminal of the coil.
Resistance should be about .3 to 1.0 ohms, and the
resistance should be the same for each checked pair.

Then check the secondary resistance by probing the
paired companion cylinders (1-5, 2-6, 3-4). Resistance
should be about 6.5 to 11.5 K ohms. (Probe where the
plug wires connect to.)

Most resistor spark plugs will have about 5-8K ohms
measured from the tower terminal to the interior tip
(not the grounding terminal).

Resistor plug wires vary according to type, but most
have about 6-12K ohms per foot of wire.

It takes a little time and effort to do these checks, but
might save some money...

 

[DontPanic]

Update...I've sinced changed the plug wires and 5 of the 6 plugs. As you guys know that last plug is a booger to get to even with extensions and alot of patience. Check engine light finally came on (it wouldn't before for some reason) so I had the guy at Autozone plug it up. Read P0306 "Cylinder misfire detected-probable cause Ignition system fault, spark plugs, or coil. Also vacuum leak, injector fault, or high/low fuel pressure. BTW the tachometer only works sometimes now---does that help narrow it down any on any of those possible reasons listed on the Code read printout? Would that tell me its likely a faulty plug or coil since tachometer is electric related?

 

[2000StreetRod]

which engine?

Do you have the SOHC or OHV V6?

Is cylinder #6 (driver side, rear) the plug you haven't changed yet?

The PCM requires a signal from the crankshaft position (CKP) sensor to know when to fire the spark plugs and to drive the tachometer. Try cleaning the CKP sensor connector by disconnecting and reconnecting it a couple times.

 

[DontPanic]

It's SOHC v6. No that plug was replaced, it was the one on the opposite side rear that I couldn't get to. Will try to clean the CKP sensor and report back. I'm getting only about 250 mikes a fill up vs. close to 300 a few months ago. Thanks for the help.

 

[2000StreetRod]

EGR valve vacuum

. . . tested the fuel pressure and it was fine (about 30 psi). . . When I pull the vacuum hose off the EGR valve there is little/no suction but when I removed the hose elsewhere (I'd have to look to tell you where) I was getting plenty of suction. . .

Did you ever test the fuel pressure again? As I posted previously the fuel pressure should be at least 60 psi.

The EGR vacuum regulator controls the amount of vacuum at the EGR valve. The PCM controls the EGR vacuum regulator. The PCM disables EGR when the engine is at idle or heavy load. That's why there was "little/no suction" at the EGR valve.

Do you have access to a device that can read the long term fuel trims? If you have a lean condition it could be due to an intake manifold leak (common) or low fuel pressure (or both).