gonna drive it off a cliff if i cant fix this gremlin!

[lilbeefy]

ok here goes, the other day i noticed my 96 ex 4.0l ohv was bucking a little at around 65mph but went away rather quickly, later in the eve, the engine started to miss bad, pulled code p0301 cylinder #1 misfire. i got her home, changed her plugs and ran her for another day before the code came back, checked the wires and all checked good, but noticed the coil pack was firing weaker on the passenger side than on the driver side. I went bought a new coil pack and replaced it, and again problem went away for a day. I have found when the engine is cold and started for the first time of the day, i can run for hours without an issue, but if i shut it off for say half an hour problem comes back, today i pulled the upper intake manifold off and found the #1 injector plug was only partially connected, reconnected the plug put her back together and no issues, shut it down for an hour and when i restarted it came back this time without a code, i popped the hood and hit the #1 injector and she smoothed right out. got it to fail again later and hitting it this time did nothing, i put the truck in gear and it smoothed out on its own. My questions are, do you think the injector is clogged, or electrically going bad? Second, how in the heck do you seperate the fuel manifold from the lower manifold? i got it to move side to side but it would not pull off, for the life of me i tried for 4 hours. Last could an 02 sensor, or dpfe sensor send this misfire code?
I doubt the 02 sensor will cause it but what do I know. I have had codes for 02 sensor slow to respond a few months back but has never came back. The reason i ask about the dpfe sensor is due to three occasions in which that sensor has failed on me. Any help would be appreciated, i am going nuts trying to solve this issue. by the way mileage is 176,000 miles.

 

[2000StreetRod]

Misfire source

The PCM computes the power of each cylinder and when one is low reports a misfire for that specific cylinder. Typical misfire sources are ignition, fuel injection and compression.

Ignition problems could be due to a bad plug, wire or coil.

Fuel injection problems could be due to a bad injector, pressure regulator, fuel filter or pump. The only problem that is cylinder specific is a bad injector.

Low compression could be due to worn/broken rings, worn or sticking valves, blown head gasket or cracked head.

I suggest changing your fuel filter if it hasn't been changed in the last 30,000 miles and then adding fuel injector cleaner to your tank. (I use only Techron). Then I would pull the plugs and check the compression (make sure the throttle plate is wide open). I would also temporarily swap #1 and #2 plug wires (at both ends) to make sure the wire isn't bad or shorting out.

An intermittent sticking valve is hard to catch. If you're due an oil change you may want to consider an engine flush just prior to your change.

A bad O2 sensor or DPFE shouldn't result in a cylinder specific misfire DTC. Other possibilities are the crankshaft sensor (it's in an exposed to elements location) and the camshaft sensor.

I can't help on separating the rail from the manifold. I've never done it.

 

[lilbeefy]

ok so i have gotten a little more info, if i let the truck sit a few hours and start it up, no issues no matter how far or long i drive. If i shut down and restart the truck say 10 minutes later, guaranteed to misfire. is it possible it is the pcm? could the crankshaft position sensor or camshaft position sensor cause a cylinder specific problem? i am tight on cash and really need help.

 

[lilbeefy]

bump.... could anyone have any clue's or have had this happen before i really need help. thanks.

 

[2000StreetRod]

heat sensitive injector

Does the misfire DTC always indicate the same cylinder? If so, it sounds like your problem is a heat sensitive fuel injector. When the engine is running the fuel flowing thru the injector cools it. When you shut it off after driving for a while the heat builds up causing the injector to fail when you restart. Some vehicles with electric cooling fans continue to run the fan after engine shut off specifically to prevent this problem.

Did you change your fuel filter and add Techron as I suggested in my previous post? If not, I wish you luck!

 

[lilbeefy]

yes i changed my fuel filter and all i could get here for injector cleaner that i trust is lucas injector cleaner, thank you for your input 2000streetrod, i am thinking the same as you suggested, i was kinda along the impression of vapor lock in that injector but your input makes more sense. i will let you know how things go, i am gonna tear it down tonight, do a compression test ( for reassurance) change my coolant temp sensor( busted) replace my vavle cover gaskets, been leaking for a year now. and remove my faulty injector. hopefully i can get one tomorrow and get it all back together. i will let you know if that is the fix. thanks again. any other suggestions would be great.

 

[lilbeefy]

well here is the update, cost $250, maintenance done, replaced fuel rail, replaced, injectors, changed all gaskets from lower intake manifold up, replace wires, coil pack and spark plugs. Is the problem fixed you ask. NO! now it is worse, but not missing anymore, it idles real rough, my 4.0l sounds like a 5.0 when you drive her, she feels like your pulling a ten ton sled. my conclusion, i believe it is the camshaft position sensor, but to be sure i am getting a full diagnostics done on it in the morning, if that reveals my suspicions i will be highly upset, THANKS TO THE ONE PERSON WHO HELPED!

 

[2000StreetRod]

Bummer!

It's a real shame that after all of your work you're still having problems. You should be proud that you got all of that accomplished for $250. The shop should be able to read your fuel trims to see if you're rich or lean which robs your power. I hope that it's something simple and inexpensive!

 

[lilbeefy]

well got it fixed, it was a bad injector, thanks 2000.

 

[2000StreetRod]

glad its fixed!

I thought you had replaced your injectors. Was one of the replacements defective?