Hey Ya'll,
I posted on this issue a couple if months ago but didn't get any feedback per say. Somethin's gotta give cuz I'm stumped. Mechanics are stumped.
History: Drove with check engine light on (small evap leak) for many years. Didn't hamper smog tests. At 161k miles, threw a rod mid Sept 03. Engine swap to 4.0 w/102k miles. Ran well except P0305 code came up. Plugs were new from swap but replaced them anyway. Still P0305. Replaced ignition coil. Still P0305. Engine running fine. Not rough. No stall. Switched cylinder 4 and 5 injectors and reset OBD2. Drove about 160 miles (highway). Light came on - P0305. Now guzzling fuel (10 gallons to go less than 100 highway miles). Took Jeep to mechanic for compression test. They didn't listen when I stated COMPRESSION TEST ONLY and per P0305 code, they replaced plugs, ignition coil, I THINK they said they cleaned the injectors, said they fixed a bunch of connection leaks on the motor, and verbally stated 150 psi all cylinders (no actual report privided). Needless to say, I was furious about charges for redundant troubleshooting (I specifically stated I was aware radiator was leaking and I would address that myself however, they went and replaced it anyway - none if the services they did were authorized and no hard copy documentation was provided... talk about a law suit asking to happen, right?). But I digress.
Meanwhile, the check engine light came back on as soon as I took off from the shop. Verified it was still P0305 (thank you Auto Zone).
So, from what I've learned, the following can be checked off the troubleshoot list:
plug(s)
ignition coil
injector
Valve(s)
Valve seat(s)
piston ring(s)

I was told by mechanic who did motor swap that all O2 sensors showed fine on OBD2 scanner.

Jeep starts without hesitation. Runs a little rough at times but not consistently. Just filled gas tank again and will know if guzzling still occuring later today. Am I down to the following as possible causes for P0305 code and can they be specific to cylinders?
Cam position sensor
Lifter(s)
Automotive relay
MAP sensor
OPDA bushings
Pulse ring

Heeeeelp pleeease!!!

ione

I would run injector cleanser through the fuel tank. I would have the cat converter flow tested. Buy an infrared temp sensor gun, and check exhaust mfld for a cold cylinder, or two. A flat camshaft will drive you cookoo, but will not have 150 psi, that seems high, on a used engine. You can borrow a compression tester at an auto parts store, and confirm what they told you. You may also borrow a fuel pressure gage. Hiring a lawyer for small claims court, gets expensive, if you lose. I use Modern off road in west Phoenix, for anything I don't want to do myself. Where are you located? Log into Facebook

 

I would run injector cleanser through the fuel tank. I would have the cat converter flow tested. Buy an infrared temp sensor gun, and check exhaust mfld for a cold cylinder, or two. A flat camshaft will drive you cookoo, but will not have 150 psi, that seems high, on a used engine. You can borrow a compression tester at an auto parts store, and confirm what they told you. You may also borrow a fuel pressure gage. Hiring a lawyer for small claims court, gets expensive, if you lose. I use Modern off road in west Phoenix, for anything I don't want to do myself. Where are you located? Log into Facebook

Thanks for the 411. I'm in So Cal. I now have a loud whistling noise coming from under the hood. Not a slipping belt or bad bearing noise but an intermittant very noticeable whistle. Arg!

 

Before I started throwing parts at it, I'd have the injectors flow tested.

 

Good tip. Tks.

 

You might stop by an Autozone and ask if they can do a compression test for you. After that, you gotta start looking at sensors: crank position, cam position, O2, etc.

 

I didn't know they did compression tests.

 

Thanks for the replies. So, since my last post, I picked up a compression test kit, watched a whole bunch of You Tube videos on how to do dry and wet test, and dove in head firat. Wasn't that hard cause I've already changed the coils 2x. Other than gettin the adapter stuck in the first cylinder I tested it was straight forward. Came back with my highest # at 180 and (drum roll) lowest was 130 in #5. It was pretty obvious that shop hadn't actually done the test. Anyway, wet test stayed at 130 so crossing worn piston ring off the list. That leaves valves.
Called the guy who did the engine swap back in Sept last year. He's stickin to his 45 day warranty expired cop out to avoid taking responsibility. I reminded him that I went to him at 38 days into that warranty to report the misfire on #5 issue (when I was trying to get it through smog, and that I can prove it with text msgs, etc.) and he strung me along over the next week, even keeping Jeep a day and claiming to have fixed the shifter spring problem (another story about an issue that came back with Jeep after motor swap) but not taking any action to address misfire issue except resetting OBD2 and telling me to drive 65 non hiway miles.. . So in response to my call to him, he called the wrecking yard where he got the motor. That guy there said warranty expired - BUT - he'd pick the Jeep up at the mechanics shop (that's about 2+ hour from where I am right now), pull the piston out and take it to the machine shop to repair.... for $300! Arg! But I told mechanic we were down to valve malfynction! Why don't these jerks listen to me?? (cuz I'm a girl... 😏).
Any suggestions at this point?

 

130 isn't great, but it should run ok. Something else seems to exacerbating this.

 

I chased a misfire code on my daughters jeep for a year 2006 TJ 6.0 automatic. Multiple mechanics. One of the mechanics is VERY good, but not a jeep mechanic that is why I sought out others. I suspected the head was bad, but the mechanics wouldn't listen because they would have to pull to inspect. The jeep had the good TUPY head already. Finally My "good" mechanic conceded that it may be the head. I bought a new one from the outfit in Florida based on suggestions from this forum (i think). Cylinder Heads - Auto, Truck, Marine | Clearwater Cylinder Head (cylinder-heads.com) The good mechanic did find imperfections that would cause the valve not to seat properly. I can't remember what it was for sure, but may have been a small crack. Anyway, it cured the issue. No more CEL for over a year now.

 

Hmmmm... OK. Thanks for the 411.