charliem3850

I recently purchased a 2004 Grand Cherokee Laredo with the 4.0 motor. It has 140,000 miles and is very clean inside and out. The only issue wrong with it when I was looking the vehicle over is that it would hesitate to start. It would crank but it would not start on the first key turn.

So far I have tried several things. I have tried cycling the key to see if it was a fuel pump issue. When I cycle the key several times it still does not always crank. I have even left the key in the on/run position for several seconds. I also want to note that it is not a hot or cold issue. If I get the motor hot and then shut it off, it very seldom will crank right back up. This makes me believe it's not the fuel pump. Am I logical with this thinking?

It did throw a code of p0340. When it threw this code I replaced the cam sensor thinking it would solve my issue. With the new sensor I still did not manage to resolve it.

I got the battery checked and it is producing full power.

Then I replaced the crank position sensor. This is is the 2nd time I have done one and it does not get any easier. The one I replaced looked almost new. However I still replaced it and it did not solve my issue. It still takes 3-4 times of turning the key to get it to start and now it hesitates in the throttle. When I go to press the gas it hesitates before it actually takes off... almost like it wants to stall but doesn't.

Then I replaced the throttle position sensor and I still am in the same boat with the same issues.

Any help would be great. I have read and read forums but I do not know what to do next. I have looked in the engine bay and I do not see any broken or loose wires or hoses.

Thanks for your help.

charliem3850

Also I want to add that I cleaned the intake with carb cleaner and that didn't seem to help. It doesn't help either if I put it in neutral and try to start it.

rgr4475

Have you cleaned all of the grounds? My wifes XJ with the 4.0 was doing this. I cleaned all of the grounds in the engine bay and it began to start better. Quick, free thing you can try. Also, last time plugs were replaced and with what kind?

charliem3850

I have cleaned several grounds. Nearly all of the ones I have touched so far have been very clean. I might have cleaned 5 to 6. I am sure I am missing some on the exhaust header side. Are there any in particular that are known to fail?

I took it up to a mechanics shop this morning and he was not able to pinpoint my issue. His reader, read "no signal from cam sensor to pcm." He seemed to believe it is my PCM and strongly suggested I buy one. Any one have any suggestions to buying a new pcm based upon my symptoms?

I ordered another new cam sensor and I am going to swap that one out to see if I got a defective one. The mechanic said that they sometimes are defective, especially the cheap ones. The parts store said they would take back my new new one if nothing changes.

Once it starts it sometimes idles rough. For the most part is runs great once it gets going.

charliem3850

If it is not leaking any oil, would there be an need to replace the synchronizer?

charliem3850

Wow! This place isn't much help anymore.

The basic symptom is it his having a hard start. It takes usually 3-4 cranks before it fires up. Once it fires up it runs good with no issues. Occasionally it will crank and have a rough idle but that works itself out quick. It usually idles well and doesn't make any unusual noise.

At the moment the check engine light is not on. It has come on maybe once or twice since I have owned it now. When it comes on it shows p0340.

I have a new syncrhonizer ready to install but haven't yet because it's not making any real grinding issues. And the one I bought didn't come with the toothpick pin whole and I cannot see the TDC timing marks on my engine. Do all jeep 4.0 motors have them. I have looked all over.

One of the mechanics I met said the pcm. But everything i read about a bad pcm says a bad pcm produces multiple electrical issues.

Seriously, any help would be great!

rgr4475

I'll respond so this gets moved up to the top of the list. A lot of what you mentioned would have been what I suggested. Once the talk gets into PCM's, I'm out as I know nothing about them. Hope you can get this figured out soon.

charliem3850

Just wanted to add that I finally heard the fuel pump today. I kept turning the key and running to the back of the vehicle to hear it. I didn't realize that I could hear it from the drivers seat. It kicks on very quickly.

Maybe that narrows it down to a PCM?

dave1123

P0340 is lack of cam sensor signal. Check the wiring for chaffs or pinches, all the pins on the connectors, and the pins in the PCM plug. Don't condemn the PCM before eliminating everything else.

charliem3850

I want to report that my problem has been resolved. After everything I have tried it ended up being the fuel filter. Now it fires right up on each crank and runs like a champ!

Hopefully this thread could be used by someone in the future with similar issues.

dave1123

Thanks for the comeback! I should have asked you about the fuel pressure. That would have been a dead giveaway. The fuel pump only runs for about 1 to 2 seconds each time you turn the key to run. That's supposedly enough to charge the fuel rail with pressure. That ain't gonna happen if the flow is restricted. The fuel pressure regulator is in the filter as well, and if that's bad can cause the same problem.