From day 1 you had to step on the gas pedal to start it. After a few months it started randomly dieing, sometimes it would start back up, other times it wouldn't for a few hours. Sometimes it just wouldnt start. It would also jerk really bad when driven lot. Changed the crankshaft sensor, then started idling really bad, dropping to 100 to 200 rpms then surging to 2000, then back down, over and over. Changed the camshaft sensor, same. Changed the tps sensor and then it would idle fine for a minute then just die. I cleaned the IAC valve. It was back to the stall/surge idle. I think I got a bunch of carb cleaner (yes, NOW I know I should have used throttle body cleaner, but I didn't know this yesterday ) inside the IAC... this morning it started right up but it sounded horrible and was shaking like half the cylinders weren't firing. Checked the codes and, p0351,352,353,354. 4 ignition coils weren't firing. Looked at the pcm, wiggled the wires, seemed fine. Pulled the negative battery cable, reconnected it, and then it was running fine, all cylinders firing? Weird. It seems better, but you STILL have to step on the gas pedal to start, and the idle flutters up and down a few hundred when the ac is running. So I just put in a new battery, still the same. And I'm still not confident it won't randomly die, because it has been an intermittent issue, and died three times and jerked once yesterday, after the new tps but before cleaning the iac. Also had catalytic converter tested and its fine. So, we have.... new crankshaft, camshaft and tps sensor, clean iac, all cylinders firing, pcm seems fine, cat is fine, new battery. What could cause you to need to step on gas pedal to start?

 

Did u try swapping coils? And seeing if the misfire moves?

 

Hello, you may already have heard, but by the sound of all those issues, and it looks like you have a 4.7L engine, that may be your issue. I heard that 3.7L, 4.7L, and 5.7L engines are no good. :-/

 

As of right now it's not missfiring. I'm probably going to change out all the coil packs and spark plugs soon anyway, but as for why I have to step on the gas pedal to start it... it's a mystery a haven't been able to solve and it's probably related to all the other issues it's had.

 

I don't know who you've been talking to, but there is nothing wrong with any of those engines! Sure, they have issues, but with proper treatment and maintenance, which some people are lacking doing, they are fine powerplants. BTW, If you'd read the title of the post, you'd know it's a 4.7 and the second year of production in jeeps!

I'll try to add my opinions after I cool down.

 

Okay, by opening the throttle, all you are doing is giving it more air, not fuel, and reducing the manifold vacuum. I suspect a MAP sensor not giving good data. Is it setting any codes besides the misfires? You can get them by the key method, that is key on,key off, key on, key off, key on and wait. The codes will appear in the odometer display. The rpm will change when the A/C compressor adds it's load to the engine, but that's not unusual. I've been told it takes around 25 hp to drive that thing!

Duh! You already told me you got those misfire codes so you must know how to do that. My bad.

 

Lol, yes. I figured out that handy key trick. Love it. It's thrown all kinds of codes since we bought it. Mostly just related to missfires, ignition coils, and the camshaft sensor... That's why I was so confused, with a fuel injected engine... I knew it was just giving it more air and the air filter is clean. I will try the map sensor next, great advice, thanks!

 

I'm going to make a suggestion. If you're willing to spend $7.99+tax on the best manual I've ever seen on your jeep, Download the FSM for your specific year jeep from pacificcoastmanuals.com It's 93 mbs of compressed pdf files and covers EVERY system on your jeep with explanations of the systems, how they work, and diagnostic procedures. You will find they are NOT separate systems, but are integrated and react with each other constantly.

 

I am definately willing to buy a manual. It didn't even have the owners manual with it when I bought it. Hopefully I can understand it. To be honest, I am just a stay-at-home Mom. I am not a mechanic by any means. I am capable, and have basic knowledge, and I'm not afraid to get my hands dirty. If you tell me where something is, I can usually take the bad part out and put the new part in. And I'm getting to know this Jeep pretty well, haha. Also, an update. Last night the check engine light came on again so I checked the code and it was p0420. Catalytic system efficiency below threshold. As I mentioned, I had the cat tested. I went to a muffler shop. I was told they couldn't even legally replace it if it passed and this is how they tested it. They had me drive it to get it up to running temp and then they checked the temperature on the front and back of the cat. They said if it were bad there should be at least 100° differance from front to back. Front was 313° and back was 350°. So, I am going to replace the MAP sensor today... but I had a thought last night. As I mentioned, the pcm isn't bolted to the firewall. The guy I bought this jeep from is one of those people who buys junkers, does a little work to them and turns around and sells them. He gets most of his parts off of junk yard vehicles. What if he switched out the pcm on this jeep with another from a junkyard? It wouldn't be programmed to my jeep and it would cause all kinds of problems right?

 

Actually the PCM may not even be grounded! What a putz!

Check out wjjeeps.com for lots of info on your jeep.

 

Oh, so how would I ground it? Just by bolting it to the firewall? I couldn't even find holes where it should be bolted, and don't have bolts to do it and wouldn't even know what bolts I would need, so I just set it back in there gently. Buy I did pull it out and open it up and look in it and all the gel in there is nice and solid, no breaks or cracks, and there was nothing that wasn't in the gel.

 

It should be mounted on 2 studs with nuts near the top and one stud that goes thru a hole in the fender sidewall with a nut on the bottom. That may a cover bracket in my picture, IDK. My best suggestion it go to a junkyard and look at one.

 

I think it's supposed to be in a bracket but there is no bracket. It's just sitting there lose behind the coolant tank. And there is no wire coming off it to ground either. Does anyone have this same year range /engine size that could show me a pic of how it should be mounted and knows where it should be grounded?

 

My DD is a 2000 WJ 4.0, but it's almost dark outside and my camera isn't ready. I'll see what I can do in the morning, and no, I don't have a cellphone with a camera.

 

So the first picture is the pcm I found sitting loose behind the coolant reservoir. Then after trying to search pics on Google of how it should be mounted, etc it seemed it should be in a bracket next to the reservoir. I look under the hood again and right there next to the coolant reservoir is what looks to be another, but differant looking, pcm (second picture). Now I'm REALLY confused.