5.7 Hemi V8 P0301 Help Please

[Regan15]

Hi,

Thanks in advance for any help,

This is quite the saga and hopefully someone can help with my heep!
I brought the 2007 grand Cherokee a year and a half ago with 40'000 km on the clock. Its in mint condition but i now know why it was traded in! It started a day after I brought it, it had a long crank then about 20 seconds later the engine light come on. As you do, i took it back to the Toyota dealership I had purchased it from and they took a look. There response was it was a misfire and they spoke to Jeep who said this happens sometimes. Most people laugh but from what I read this is actually true!!!! I didnt believe it but thought Id take it and see how we went as it doesn't miss a beat apart from the starting. I ended up taking it to jeep when it happened again because apparently they have awesome diagnostics?!?!? (yeah right!) Its been at the mechanics i'd estimate over 6 months now. I work away out of town for long periods so its not an issue! Well it wouldnt be if they could fix it! I have a aftermarket warrenty as new due to "the good condition of the car" so it hasn't cost to much. The code is always P0301 cylinder 1 misfire and the only symptom is long cranks and has stalled twice at idle but then its perfect! Jeep changed round all the coils and injectors involved with the cylinder but the problem never moved. I had all new (16 total) spark plugs the correct copper type installed. No difference. Full major service correct oil ETC! still happening sometimes. They check numerous things couldnt fault anything so they involved Jeeps engineers who come back with a possible lifter issue. So they completed leak down, compression tests and said thats the problem so off came the heads all lifters replaced. reset computer and as usual after 2 days the problems are back. Always 2 days after PCM reset usually. When its a bad start i noticed the windowscreen wipers would go up and down too?? I told them this and told them i think its possibly electrical like faulty PCM. Finally the engineers decided to change the PCM. I thought that would work but it didnt and now yesterday I had it taken back to Jeep as i'm still not home. They reckon they have rewired and they are hinting this is 2 hard basket for them. Today they put some fuel system cleaner through the fuel rail and apparently alot of carbon/black smoke came out the exhaust?? this seems a very minor thing to do at this stage after these major repairs. The fuel pressure has been checked and monitored and no problems also. I asked them to check the EGR valve is not stuck open and i'm wondering if the twin spark is an issue as I have read else where. Ppl saying they have installed the conversion back to sparking both plugs at once on each particular cylinder. The other option is maybe something to do with the MDS but I doubt that? I'd love any advice as this is doing my head in and now to top it off the mrs engine light in her holden astra has come on tonight after a lot of repairs already but i'll move forums for that!

Thanks again

[timbotrog]

How about a minor break in the wiring loom running to the coil causing an intermittent problem?

[Clarky]

Read this?
http://www.jeepforum.com/forum/f67/4...-coil-1409791/
Maybe it was babied from new and is fowled with carbon as this post suggests.
Take it out and drive it hard, it mightn't fix it but you will get rid of some frustration.
My CRD always runs better after you get the temp up and drive at freeway speed in 4th as if you were towing for an hour or so.

[Regan15]

Yeah maybe carbon, but with the lifters being replaced and the heads polish ETC would all that not be clean? I'm on another Jeepforum and someone is suggesting similar problems and it was catalytic converter after no one could figure it out!

Jeep tells me they have replaced all the wiring to the coil pack ETC, but am I to believe this goes to a wiring harness that they prob haven't replaced? I was told the twin spark system can cause issues when it gets a lil older. I'm tempted to buy some taylor shorties so both plugs are firing on each cylinder when its due. Any thoughts on this? I'll speak to jeep tomorrow and ask about catalytic converter. Is there even a way to check with out just replacing?

Anyone no much about the O2 sensors. There is 2 upstream and 2 down? I took it to a mechanic that used to work on jeeps and he plugged it in and said from memory the 2 downstream o2 sensors should be switching like the upstream but they weren't. I told jeep this and they said this was normal?

Thanks

[Regan15]

Morning,

We'll not much to update but they have done a full clean by pumping 100 octane fuel with a cleaning additive through the engine and blowing out a lot of carbon build up apparently. I pick it up tomorrow. I'm a little confused why at this stage we are doing something simple like that?? Wouldn't that be first on this list.

He thinks all sensors are acting correctly, even the o2 sensors so they don't think catalytic converter. So would we be to think its an intermittent sensor causing these bad starts sometimes? Is it just a matter of replacing them?

They told me the jeep is low on fuel the other day and in order to test it they will have to fill it up at my cost! I haven't seen it in months it's all there problem I would have thought! I run 98 octane I'm it. Is there any issues regarding which fuel is used?

Thanks

[loader]

my wj was doing the same as yours turned out to be the check valve in the fuel pump letting fuel run back into the tank they need aleast 30 psi to start mine was no pressure so long cranking then engine light on jeep wanted 600 bucks new pump i got a after market 100 psi pump with regulater it now starts first go every time i have it at 80 psi running. it gets better fuel ks and screems now
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[Regan15]

Yeah, I believe fuel pressure issues would fit the symptoms.

I had the jeep back for 5 days. I drove 1300 km had no bad starts for the first 3 days, but I had always kept the fuel take above half. From memory its always pretty good for first few days. May or may not be relevant. After that I finished a trip at quarter tank and the next morning went to start it and it was a long crank and struggled when it started for a few seconds. Same the next morning. Then I filled it up and drove it home which was 400 or so km and parked it on the lawn. 2 hours later I went to move it from lawn to garage. It struggle and then stalled. This was with just under half a tank. I have done similar this morning but the start seemed fairly normal. No engine light yet which is odd.

I dropped at jeep and said maybe try crankshaft sensor but they are sure it would throw a code straight away for that. But they are still going to do it to see. They are going to check fuel pressures but he said they checked for back flow etc.

Really over this.