A little background:
Ive been trying to diagnose this problem for months. I've had input from mechanics, jeep owners, friends, ect. The hard start has been an issue for years but the bucking and shaking started last summer. Also after it started, I invested close to $1,000 in doing all of the neccessary maintenance and replacing alot of parts to try to fix it such as the fuel pump, injectors, throttle body, IAC, all filters, plugs, wires, cap and rotor, water pump, radiator, speed sensor, ect. I have a CEL for a coolant temp sensor, which I've replaced more than once, and the rear o2 sensor, because it was removed with the cat.

Symptoms:
Hard start. It will not start without giving it gas and holding it for about 30 sec. If you let off the gas it idles low and very rough for a min and if it doesnt cut off, it smooths out.
Bucking/Shaking. Randomly while cruising it starts to jerk like it's going to shut off but the rpms stay steady. The bucking will continue until I get on the gas pretty good. Then it clears right up but will come back randomly. There's no rhythm or way to repeat it. Some days it doesn't do it at all.
I'm lost. Any help is appreciated but I'd rather not just keep throwing parts at it.

 

That's a lot of parts mate..

Assuming they're all working out of the box;
I miss the parts that commonly cause these symptoms, namely the CPS, Cam (and perhaps even Coil)

And: if you cleared the code but it comes back, you haven't solved the issue.

 

The jeep had been sitting for almost a year prior to me taking it over and hasn't been shown much love so I figured I would do it. Like I said before tho, it was doing it prior to all of the new parts. So I dont think it's related to them. I'm no mechanic tho, so I've just been replacing what people have recommended. I guess I'll give the CPS a try.

 

You had a lot of recommendations!

But like I said, the CPS is always high on the list...

 

Well most of the parts were replaced simply because I had the money and wanted to invest a little into the jeep, also it was not well maintained so anything I did could only help. The recommended parts were like the fuel pump, fuel filter, speed sensor, rust/water in the tank, ect. It's like 50/50 maintenance and recommended. I just want to be able to drive it without worrying about it having a seizure half way down the road. Lol

 

You need to go through the wiring and grounds (including the one in the trunk, drivers side, behind the trim panel) and ensure there's nothing wrong with any of the wiring and that all the connectors, grounds, battery cables are all nice, clean and tight.

I'm also "not a professional mechanic", but I've been around here long enough to see the common behavior of folks "firing the parts cannon" when something is not working and it's unclear exactly what is wrong. I may have been guilty of it myself once or twice... Anyway, do yourself a favor and go over the Jeep carefully, thoroughly and slowly checking all the ground points - clean contact, tightly fastened... all the connectors - pull them apart, clean them, reconnect them.... all the wiring - is it flexible, intact sheathing.... Do the same for the vacuum lines... ensure the rubber is soft and flexible, not cracked/split, and tightly connected.

You cannot really do any serious troubleshooting of a tough/inexplicable issue until you have done this and know you're working with a solid baseline. It's no good putting a new CPS on a Jeep when one of the wires is shorting out on the body a bit down the line....

The grounds are particularly important and easy... the main one is usually right around the ignition coil and there's near the battery, there's the one in the trunk behind the trim. The flexible strap at the back of the engine is for radio interference... good to check, but less vital than the others. Clean and tight. Battery cables can get corroded inside so they look OK, but are not so good... they are usually stiff and gross feeling when that happens... good cables and connections are really important... it's worth putting a new set on as a maintenance item if you're unsure.

 

Unfortunately firing the parts canon at the Jeep with Chinese parts, you can end up with worse quality than an aged original part and create more problems CPS sensors in particular..

I second checking the wiring. In particular the harness at the back of the engine to the firewall, and anything near the exhaust. Open up the wiring look and really look, as fatigued or melting wiring might not be obvious. Fix the CTS sensor code, as that can affect cold starting.

 

Actually I don't use chinese parts that matter, such as the fuel pump, sensors and ect. Also I did check and clean the grounds as a part of the maintenance, including the ones by the ignition coil, battery, and on the fire wall. I was not aware of the ground in the rear tho. I'll have to find it.

 

Have a look at post #4 in this thread
https://www.cherokeeforum.com/f2/rig...orking-223682/


Think fuel pump module ground would be the only relevant one for your in that back area if you think what's involved in how the engine is running.