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Discussion Starter #1 (Edited)
Bought this Jeep, spring of this year. I was excited for my first Jeep, but did not know what was to come. About a week after buying it, check engine light comes on. P0300 P0304 P0308. Missfires. Replaced spark plugs, did the oil change and filters. Cleared the codes. After this it was running fine but the check engine light came back on with code p1294. Which is target idle not reached. I think when I did the spark plugs and removed the throttle body I must have not aligned something right. So other than a high idle, I did notice my coolant reservoir was empty so added 50/50 mix. A couple days later, I went out of town and the Jeep sat for a few days, when I came back tried to turn it on, It just cranked but did not start. So I started by the battery, checked voltage and it was good, checked all fuses, fuses were good, checked relays, relays were good. (Although I am mechanically inclined, I am, by no means a pro at this. Other than a multi meter and a full wrench/ socket set. I don’t have any specialty tools or testing equipment so I’m limited to what I can do) I’ll try to wrap this up quick. Replaced fuel pump, fuel filter, crankshaft sensor, camshaft sensor. After a couple months of testing and research, ended up ordering a new PCM. When the pcm came in my battery was completely dead. Charged it up. Plugged in the PCM followed instructions and fired right up!!!! Yes!!! .... after a few minutes of being on,
Idle dropped to about 700rpm. Which was great. No weird noises or unusual shaking. Well then I noticed it was puffing a white cloud. Shut it off checked my oil... great white slime on top of my dipstick. Checked my radiator, reservoir is empty again, and radiator cap is rusty looking, not a pure 50/50 mix. Now it doesn’t turn on again. Cranks but does not start.
Any suggestions please????
 

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......Shut it off checked my oil... great white slime on top of my dipstick. Checked my radiator, reservoir is empty again, and radiator cap is rusty looking, not a pure 50/50 mix. Now it doesn’t turn on again. Cranks but does not start.
CEL codes?
Any sign of coolant puddles under the Jeep, the engine, radiator, reservoir?

White or chocolaty residue in the oil coupled with losing coolant is not a good sign.
Sometimes white smoke in the exhaust could be from condensation in the exhaust system but the white slime in the oil and losing coolant is troubling.

If its not a coolant leak somewhere like the radiator, more than likely its a bad head gasket, cracked head, etc. which will cause the white slime, coolant loss and excessive white smoke out the exhaust.

If you're lucky could just be a coolant leak and the white oil slime is from condensation in the engine especially if its been sitting for a long while.
The quickest way i know of to conclusively determine the cause of the coolant loss, the white smoke and white slime is to have a coolant pressure test done.
 

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Discussion Starter #3
At this point im not getting any codes. I’m assuming head gasket just because of the white slime on top sitting on top of my oil. I also removed the spark plugs and even tho I changed them about 500 miles ago. It looked like they been in there 5 years. There’s no sign of oil on them but they are black all over the tips some had some residue but not sure what it is. I cleaned them with some seafoam but I’m thinking on changing them again. Still not turning on.
 

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Sounds like you have multiple problems maybe possibly caused by one culprit.
If the plugs are fouled enough that could be your starting problem but i'd first find out why they are fouling in such a short time.
Black fouled plugs are typically due to a rich fuel/air mixture but throw the coolant loss/white smoke into the mix who knows whats going on.
Have you done a compression test on each cylinder?
Have you checked, cleaned or changed the IAC valve or EGR valve if equipped.

If this were my deal i'd get the coolant pressure test done which could steer further trouble shooting in the right direction.
Might even try re-installing the original PCM after cleaning or replacing the plugs and see what happens.
PCM replacements can be tricky in some cases.

Hate to say this but its starting to look like a major engine repair or replacement.
Get or do the testing including the coolant pressure test yourself and stop guessing.
Most or all of the testing stuff can be rented or in some cases free from chain Auto part stores with a returnable deposit.
 

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Discussion Starter #5
Thanks, I just found out I can borrow the pressure gage form the parts store. That is my next step. I have not done the IAC valve. I’ll update after the compression test. Also I will be buying new spark plugs and see if that helps starting up. Maybe that can engage any codes that may lead me to the right direction.
 

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When you take the plugs out (again) run a compression test ( can borrow those too) on each of the 8 cyls. Pull the fuel pump fuse before turning the key. PSI should be consistent among the 8.(+ or - 10%)
If coolant in combustion chamber, it will 'wash' the plugs and no oil will be seen.
Hopefully, your PSI's will be up above 160-175. If not, HG, valves or rings. See 'wet' test in link to determine which if not HG.

Just one 'over heat' ( insufficient coolant) will see the HG get crushed by the alloy heads on the iron block (differing metal expansion rates) and not uncommon. If it is the HG, is a good opp to have the heads refreshed and its a satisfying job--just takes time- Get the Haynes manual for sure and study carefully the timing chains and tensioners are tricky but I reckon you'd enjoy.
Last item to consider: That timing case in front on the 4.7 is vulnerable to corrosion if coolant changes are ignored. At the water pump channel that's behind the pump impeller, the casing can corrode away and introduce coolant into the engine! Further, if there are pinhole to small holes from corrosion, the H20 pump can't do its job--just spins and /aerates the coolant and amplifies the trouble.
Good luck and let us know what you find with the diagnostics!
 

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Discussion Starter #7
Thanks, looks like I’ll be doing some testing this weekend. Thank you for that wet test guide. I’ll keep you guys updated once I do the compression test.
 
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