Help! 96 x 4.0 ohv P0302. . .

[KC]

I have searched but haven't found anything to help me yet, so here. we go. My son has a 96 X with a 4.0 OHV. Apparently it has been rough idlng & missing for awhile (NOW he tells me!) but it got worse recently and threw a P0302 code. I tried driving it and found that under a load, it runs like CARP!! I have tried several things but the problem presists. In sequence I have done the following:

Swapped the plug wire with #1 - no change.

Swapped the plug with #1- no chage.

Sprayed starting fluid around the intake and did not hear any change in idle speed.

Started thinking injector but was dismayed to find the injectors sandwiched between layers of the intake manifold (???), so I tried the Seafoam thing with half into the intake via the PCV valve (I know, that doesn't go through the injectors) and half into the tank wich was only 1/3 full. Still no change but there hasn't been many miles put on it yet.

So then I realized that while I couldn't swap the injector easily I could unplug it, so I did. The rough idle symptom only got worse. Plugged it in, a little better. Unplugged again and ran worse. So the injector is working, although I don't know how good.

So now I'm thinking the worst - valve, valve spring, rings, head (it does not steam out the tailpipe so I'm not thinking head gasket) so I do a compression check. It performed exactly as the #1 cylinder did. First stroke 90psi, 2nd stroke to 120 so I'm thinking the cylinder & valves are OK.

Back up a bit and think "OK it's gotta be spark or fuel". I think it would be odd for one out of six in the coil pack to go bad, but stranger things have happened so today I bought and installed a new coil pack. The problem improved a bit but the misfire is still there and the P0302 code is "pending" after clearing it out and driving it around the block.

Right now it is smoother at idle and smooth just above idle but if you put a load on it such as driving uphill it is obviously misfiring and stumbling.

Any opinions? Am I looking at injectors? I have heard of someone on Ebay selling injector rebuild kits for these - any feedback on those? If I have to tear it down to get to one injector I may as well deal with them all at the same time, and if they work it's probably alot cheaper than all new one's - if the kits work.

I should also mention that I had replaced the lower intake and upper plenum gaskets (Felpro) last year for a P0304/losing coolant issue, so the gaskets are relatively new, and it had been running good.

Thanks to all in advance!

 

[2000StreetRod]

Engine misfire procedure

P0302 Cylinder 2 Misfire Detected
Is P0302 the only DTC set?

I was going to suggest that you try my Engine misfire procedure but you've done just about everything suggested in it.

Personally, I won't put anything in my tank except fuel and Techron fuel injector cleaner. I think Sea Foam in the tank dissolves too much of the crud that has accumulated in the bottom of the tank and does more harm than good. I suggest that once the Sea Foam treated fuel is burned that you replace the fuel filter and then add a bottle of injector cleaner. I would wait until you've burned the tank of Sea Foam treated fuel and at least half of the tank with injector cleaner before replacing the fuel injector. My Bosch book says injector cleaner may take up to 200 miles to work.

One way to tell for sure if the injector is bad with little effort is to perform my Idle adjustment procedure so the engine will idle with the IAC valve disconnected. Then insert a small spacer between the idle adjustment screw and the stop to temporarily increase the idle speed enough that the engine will run on 5 cylinders. With the IAC valve disconnected the PCM will not have control of the idle speed. Measure the idle speed with all 6 cylinders and compare the drop with only cylinder #2 injector disabled vs only cylinder #1 injector disabled. If the drop for #1 is significantly greater than the drop for #2 then you know your problem is the #2 injector since you've already eliminated the #2 spark plug/wire and compression.

Another thing to try (long shot) is to connect and disconnect the CKP sensor electrical connector a few times to clean the contacts. Usually, a faulty CKP sensor results in random misfires instead of a specific cylinder.

I would also clean the MAF sensor with MAF sensor cleaner. There's a remote chance that all of the cylinders are on the verge of misfiring due to a dirty MAF sensor and cylinder #2 is slightly weaker than the others and being the only one identified by the PCM.

 

[KC]

Thanks for the info! The P0302 is the only one set. It did have one additional to this - I'd have to look up the exact code but it was EGR flow too low and I found a cracked vacuum line to the egr which has been repaired. I have not found any other vacuum leaks nor do I hear anything that sounds like one. That code is cleared and has not returned but the P0302 keeps repeating.

I will look into and try the idle procedure you mentioned, and good idea on the Seafoam/fuel filter. I'll try some injector cleaner as well.

Any ideas on the Injector rebuild kits that might be out there?

 

[2000StreetRod]

injector source?

I'm sorry but I don't have any first or second hand knowledge on new or rebuilt injectors.

Did the misfire first show up after the EGR vacuum line repair?

Was the cracked vacuum line the one that connects the EGR valve to the EGR vacuum regulator?

If you clear the misfire code does it get set when the engine is idling?

 

[Runnin'OnEmpty]

Maybe check for a vacuum leak at the PCV valve,
or a faulty brake booster diaphragm.....?

Just throwing out ideas.....

 

[KC]

Thanks again StreetRod!

The vac line that cracked open was the green line that goes to the top of the EGR valve itself. When my son first had the codes read (before I got my own scanner) apparently it was only the EGR code (but since I ws not there and they didn't print or write anything down). I fixed the leak and it seemed to run OK, but with a slight stumble which I think it has had for awhile now. He drove it about 200 miles and he said the light came back on. That was about a month ago and the misfire has become worse.

I can't guarantee that the P0302 showed up afterwards but it appears to be the case. Now that I have my reader I can say that is the only code that shows.

I don't know if the code will set when idling - I do know that after I cleared the code after installing the new coil pack it quickly showed a pending code (the P0302 again) without moving the car but I was reving the engine some to see if it was still running rough. Then I cleared it again and it stayed off until I drove it up the hill that I live on.

 

[KC]

Maybe check for a vacuum leak at the PCV valve,
or a faulty brake booster diaphragm.....?

Just throwing out ideas.....

Throwing out ideas is what I'm looking for at this point! However I think a vacuum leak at the PCV or brake booster would affect all cylinders, not just #2, which seems consistent. But again stranger things have happened! I'll try spraying some starter fluid around the booster, and take a vacuum reading again. I did previously but don't remember what I saw.

 

[ranger7ltr]

Have you checked or changed the fuel filter....

"I have searched but haven't found anything to help me yet, so here. we go. My son has a 96 X with a 4.0 OHV. Apparently it has been rough idlng & missing for awhile (NOW he tells me!) but it got worse recently and threw a P0302 code. I tried driving it and found that under a load, it runs like CARP!! "

This is the same symptom I had with my 99 X when the fuel filter was clogged with crap from inside the tank...If I drove it long enough it would set a misfire code...When I pulled the inlet side of the filter the fuel that came out looked like coffee...And the fuel pressure was sufficient at idle to run the engine but as I opened the throttle the pressure died off and the engine would die if I held the throttle open long enough...

You have spark since the engine is running; Is it running smoothly or does it vibrate and shake like a cylinder is missing? And what is the fuel pressure as you open the throttle and try to accelerate the engine? If the pressure drops as the rpm start to come up, then you have a fuel delivery problem...First place to look is the filter and/or fuel pump...

And since your truck has the returnless fuel system, the operational pressure is even more critical...Nominal pressure is 65+/- 7 psi...

BTW here is a thread outlining most of what you are seeing with this truck...And I started getting P0304 codes until I dropped the tank and filter...http://www.explorerforum.com/forums/showthread.php?t=241939

 

[KC]

UPDATE, Now getting P0304 as well!

I know, it's been awhile and I've been trying to let it take care of itself (HA!). To recap, I've changed plug, wire, coil pack, fuel filter. The trucks been running OK, just the stumble mostly at idle or under heavy load. Fule mileage hasn't been affected by much and I don't think its been losing water.
But alas, last weekend after the X had been sitting for a couople of days my son tried to start it and nothing. It turned over but acted like no fuel. You could hear the fuel pump running when the key was turned. I tried cranking it with about 1/2 throttle and after about 15 seconds it sputtered, caught and started running but really rough. After revving it a few times it was running better but now with obviously another cylinder misfiring.

Frustrated, I told him to go drive it down to the local repair shop to find out about a diagnostic estimate. (I'm about ready to give up & pay someone!) On his way down there he told me the CEL started blinking again so I'm thinking another potential clue.

Well now we are back with a P0304 code along with the P0302. Now I'm wondering if the lower intake manifold gasket has failed again and is leaking!

I will be going out this morning to try and see what might have happened with #4.

Anyone with ideas and or input to my problem?

 

[KC]

Wow, lower intake is apparently leaking AGAIN! I used the Ford gasket and followed the procedure as was recommended on here and it only lasted two years. I pulled the #4 plug and it was soaking wet and the radiator was very low.

I guess I either tear it all down and do it again (this time going throught the injectors with hope to cure the #2 misfire), pay someone to do it or just sell it off as is and let someone else do the work.

Anyone in the S.F. area want a "project" X?