03 Limited 4.6V8 Hesitates/Misses

[hpfiend]

Hey all,

My dad's 03 Explorer Limited V8 has been missing/hesitating lately. There is no Check Engine Light. The only code we have had at all was a coolant temp too low and that was a while ago and we changed the thermostat and never had it show up again and it was not missing then. He has had several tanks of gas through it and has added stabil/sentry fuel stabilizers as he thought it might be water in the gas. He has about 60K miles. The problem is intermittent as some days it is just fine and others it misses like crazy.

Any ideas?

Fuel filter he has purchased but not installed yet. Could it be the spark plugs?

Thanks,
Andrew

 

[hpfiend]

forgot to mention gas mileage is down about 2 mpg as well...

 

[bookbinder]

No codes at all? Interesting. I would certainly look at all the usual suspects, i.e.,

fuel filter, vacuum leaks, coils, plugs, COP boots (the rubber breaks down and minute cracks will cause misfires, spark tracking), MAF clean?,

one more thing if you change the plugs BE SURE you torque them to specs. These engines are notorious for spitting plugs.
Rick:exp:

Check #8 (driver's side rear) for moisture in the plug well causing arcing. If present change the boot.

 

[hpfiend]

No codes at all? Interesting. I would certainly look at all the usual suspects, i.e.,

fuel filter, vacuum leaks, coils, plugs, COP boots (the rubber breaks down and minute cracks will cause misfires, spark tracking), MAF clean?,

one more thing if you change the plugs BE SURE you torque them to specs. These engines are notorious for spitting plugs.
Rick:exp:

Check #8 (driver's side rear) for moisture in the plug well causing arcing. If present change the boot.

Thanks Rick! He has cleaned the MAF with MAF cleaner as we originally suspected that... he has no light but I will hook up the code reader to be sure...

I would think a dirty fuel filter would cause problems under load as well and be consistent? We will definitely check the coils/COP boots and plugs- especially #8...

Thanks!
Andrew

 

[hpfiend]

verified last night- no codes per an actron obdii code reader

 

[bookbinder]

Fuel filter could well be the culprit. I would further check the fuel pressure and regulator. I will have a PCM/Emissions Diagnosis Manual for 2002 Ford Engines in a day or so. Also found this:

http://www.explorerforum.com/forums/showthread.php?t=217062&highlight=replace+elbow

No codes:scratch:

Check vacuum and compression

 

[hpfiend]

Fuel filter could well be the culprit. I would further check the fuel pressure and regulator. I will have a PCM/Emissions Diagnosis Manual for 2002 Ford Engines in a day or so. Also found this:

http://www.explorerforum.com/forums/showthread.php?t=217062&highlight=replace+elbow

No codes:scratch:

Check vacuum and compression

We will change the filter- I am thinking the fuel pump may be on the way out as it is an intermittent problem. I will check that elbow thanks!

 

[bookbinder]

an easy check of the regulator is to pull the vacuum line from the regulator while engine is running. KEEP A SHOP CLOTH READY. if fuel comes out then regulator is bad. A fuel pressure gauge (can be rented) will come in extremely handy. Check before and after filter replacement. You will be amazed. If I remember right there is also a thread on pump replacement but I have not followed that one. Please keep us posted. Rick

 

[bookbinder]

Just received my manual and the first thing it indicates to check with these symptoms is the DPFE transducer/sensor which has two vacuum hoses and a three pin plug up near the firewall side of the engine.

EGR Valve not seating
EGR vacuum regulator solenoid vent restricted
damaged regulator solenoid

we can go further but you will need to access the DPFEGR PID and note voltage KOEO and then KOER Rick

 

[Curtis]

pull the coils and plugs

My dads 02 was missing intermittently, sometimes it would throw a mis-fire code, sometimes not. Finally when we could reproduce at the garage they found water down in the spark plug hole. Dried them out, a dab of silicone around the hole and insert the coil again. No more missing after that.

Its a cheap thing to check

 

[bookbinder]

Agree with Curtis. This was part of my problem on #8 (plus the bad boot). Dielectric grease is the COP's best friend. High temp boots from NAPA's Belden Wires line are awesome. Rick

 

[bookbinder]

Update???

 

[ravens1592]

definitly your spark plugs, hands down.

 

[hpfiend]

I didn't notice all of the followup replies to this and had even forgot I posted it until I was searching for my current thread on a similar problem - I apologize... last time it finally set an EGR code and we found it to be the DPFE sensor which we replaced and had no problems again until this spring... and now it is missing again and stalling if at idle rpms. Again no codes or light and I bought a fuel pressure gauge and it reads around 67 psi no matter - interestingly pulling the vacuum line to the regulator didn't seem to make much difference- no fuel squirted out but again the pressure didn't go up either? no change in pressure with the misses. It also randomly makes a single digital beeping sound with no lights on the dash or messages on the DIC- similar to if you push a button on the DIC though. It seems to do it after it reaches running temperature as well. I will check the boots again.

 

[alpha141]

Did you find out what the problem was this time? Mine is doing the same thing. How do you check the egr pressure switch?

 

[hpfiend]

Turned out being a bad IAC motor. We had previously tried cleaning it out with brake cleaner and ultimately bought an OEM replacement. as we were told the aftermarket ones are not as reliable. This fixed the majority of the issues- we also found #2 cylinder was randomly dropping out as a friend had a very good diagnostic scan tool that could do a real time graphical cylinder balance test so we changed that later and it now runs like a top. We also had changed all of the plugs and boots previously which did not fix the issue.

There was a check engine code that I typed in here in the search box and the dpfe sensor material came up in the results- I did not test it iirc, we changed it and that code never came back.

 

[2002GreyHD150]

for those reading this.... read my reply in this thread as well:

http://www.explorerforum.com/forums/showthread.php?t=337474

Also for those with 04-05 4.6's the DPFE is not on our trucks. Its built into the EGR. So if you get the EGR code, replace the EGR unit... $60 + $6 for the metal shim gasket.

above all else, SKIP the damn platinum plugs and if you think coils... do these:

http://www.ebay.com/itm/Ford-4-6L-1...es&vxp=mtr&hash=item45f55980bc#ht_1859wt_1037

Pro-Comp (yes the suspension guys) have these occasionally as well. $109 for 8 coils... I have them on our Monty, now 30,000 miles solved all my issues. Higher spark than the MSD's they are copies of, I had to buy a set of used F150 take offs to get me by until Pro-Comp had them back in stock. My neighbor has the MSD's on his Mustang GT, the manufacturing #'s on the bottom of the main red body are identical. Same source as MSD for 1/3 the price... HEck even summit is getting them in the $225 range.. which is $30 a coil... as opposed to $70+ a coil stock replacement or MSD's pricing...

Rob