[BillB7581]

Chrysler had that one bulletin abot the valves carboning up and causing a misfire... you could get a can of Top Engine Clean from Mopar or just some Seafoam and give that a shot. I would exaust all the cheap/free possibilities before changing out random sensors. It's seems like you have a valve sticking or not seating and the ECU is picking up a misfire on that cyl because the valve isnt closed. You could perform a leakdown test if you can get your hands on the tool. Making sure the valves are seated when #4 is at TDC.

[Dcoy]

Originally Posted by BillB7581

Chrysler had that one bulletin abot the valves carboning up and causing a misfire... you could get a can of Top Engine Clean from Mopar or just some Seafoam and give that a shot. I would exaust all the cheap/free possibilities before changing out random sensors. It's seems like you have a valve sticking or not seating and the ECU is picking up a misfire on that cyl because the valve isnt closed. You could perform a leakdown test if you can get your hands on the tool. Making sure the valves are seated when #4 is at TDC.

I would have to agree with you about the valve sticking But I would think it would act up as soon as I started down the road in the morning. This problem happens a mile or so down the road and what would shutting it off and starting it back up do to a sticking valve? I want to lean more towards a sensor going bad or fuel related but who knows man. I got an anolog meter and going to check my TPS later today.

[BillB7581]

I believe the bulletin says the problem occurs fully warmed up under partial load (the one pertaining to decarboning the cyl head and rotating the valves).... other than cam/crank sensor sync which sensor is going to always cause the same cylinder to miss?

You have the cam sensor telling the pcm when TDC is on cyl 1, and the pcm uses this info to ground the coil packs accordingly.

[buildin1XJ]

Have you tried checking for power to the # 4 injector? your symptoms seem to indicate something is wrong with thaT CYL ONLY. so FUEL FIRE AND COMP are a good place to start. Also make sure the Cam sensor is indexed correctly.

[Dcoy]

my problem happens after my jeep sits for awhile, like over night or after work and it will start and run fine then after driving a mile or so down the road the engine light starts to flash and it starts missing and idling rough and wont go past 3k when you get on it. then if i pull over and shut it off and restart it it will run fine. I guess I kind miss read your last post and plan on picking up some sea foam ( cheap thing to try ) and see what happens. while messing with this thing I have began to notice a little hiccup i guess while its ideling so all I can do is try..... Thanks again for the help BillB7581

[buildin1XJ]

Well I would say x1 on Tims post as the TPS can do some very unusual things due to heat and climate issues.

[BillB7581]

I dont think a TPS would set a code in the same cylinder every time.

Did you try spraying carb cleaner around where the intake manifold goes to #4? Just another idea I'm throwing out. Possible intake leak right there at #4 leaning the thing out. It's another free thing to check. Do any other vaccuum lines tie into the intake manifold right there?

It sounds like whatever is happening is only happening once it gets the O2 sensors heated up and into closed loop.

[Dcoy]

I can try the carb cleaner, and there are 3 vacume line on the far side ( furthest side away from head ) on the intake, all seam fine. I just put some sea foam in it and ran it some....then cleared the codes so ill see what happens tomorrow morning, also might just go buy a tps tomorrow....whats another $45 into my old girl! Just to throw it out there I always use to get a engine code of a very small evap leak, but never noticed anything different so never bothered with it, maybe something small turned into a headach

[Kalali]

I'm watching this real closely. I'm also having the same pesky P0304 code and have exhausted all possible options. I've got a new head, new coil, new plugs, swapped injectors, and no luck. Someone had said they had a similar issue and replacing the exhaust system solved the problem. My symptoms are different from the OP so the root causes are probably not the same.

[Dcoy]

Originally Posted by Kalali

I'm watching this real closely. I'm also having the same pesky P0304 code and have exhausted all possible options. I've got a new head, new coil, new plugs, swapped injectors, and no luck. Someone had said they had a similar issue and replacing the exhaust system solved the problem. My symptoms are different from the OP so the root causes are probably not the same.

dont worry fellow p0304 brother, I will keep you posted if I ever figure this gremlin out.

[Dcoy]

Well I didnt make it 200 yards down the road and the engine light started flashing, ran fine till about 1/2 mile from my house then I had to pull over and restart it. Ran fine the other 13 1/2 miles to work.

[BillB7581]

Very odd.... was this after Seafoaming it?

Are you actually clearing the codes or just disconnecting the battery? I have no idea whether this makes a difference or not, but the computer may lose some of it's mapping if you keep disconnecting the bat.

I would try barring the engine over to TDC and see if that hole lines up in the cam sensor drive.

[Dcoy]

Yep

[BillB7581]

I wonder though if you're on to something with the Seafoam, since it exacerbated the problem.. . you weren't even into closed loop and the thing picked up a misfire on 4. I wonder if hitting it with seafoam again would help, or getting it good and hot, stalling it out with the seafoam or top engine clean and letting it sit for several hours. It's like you moved the carbon but didnt clean it out ... I could be all wet though.

[Dcoy]

its a $6 thing to try what the h***. Have you ever heard of removing the large vacume line off the brake booster and placing it in a can of seafoam to get it into the intake and all the vacume lines. Guy at work mentioned it.