Zachariah Taylor

So I've had this 97 Grand Cherokee Laredo for about six months now. I'm self taught in maintenance of every vehicle I've owned either with a Haynes manual, forums, or both; however these don't always help with everything and it's sometimes best to get specific help. My issues began a couple months ago when my jeep started acting up seemingly out of nowhere. Rough idle, often stalling, and loss of oil pressure (according to the gauge) after decelerating from highway speeds. I put it on the OBD and it gave multiple misfire codes, a oxygen sensor code, among others. Grasping for solutions I started small and worked my way up. I replaced the spark plugs and did another oil change(wasn't scheduled for another 2k mi.) and replaced the pcv valve and hoses, which lessened the symptoms but they still remained. I then replaced the crankshaft position sensor as I was under the impression it may be originating from a timing issue; same result, lessened the symptoms but they still persisted. Still showing multiple misfires I considered changing the camshaft position sensor but decided to spend some more and replaced the coil rail (not cheap by my book but not breaking the bank). I was pleased to find that all symptoms and codes went away and thought maybe I had it in the bag. About a week and a half later the rough idle returned followed by stalling at idle here and there. Put it back on the code reader and it only showed one code for multiple misfires but no specific cylinder whereas before there was a slew of codes showing each cylinder that was misfiring. Throughout this timeframe I've noticed an increased burning of coolant (about a quart every two week) burning oil about a quart every two weeks, oil on the pcv out (the new one) and oil pressure drop happens after slowing to stopping from highway speeds. All this combined with the rough idle and stalling all in spite of what I've done to it has me scratching my head and also worried I've bought a dying jeep. Any and all help and advice would be greatly appreciated right now as I'm at a loss.

rgr4475

What engine?

What did your oil look like when you changed it? Reason i ask is if coolant is disappearing and your positive you have no leaks, they is usually the sign of a head gasket and your oil will be milky.

Zachariah Taylor

No offense intended here but you must think I'm pretty dense to not notice or mention muddy oil. If I can't diagnose a blown head gasket then I have no business doing my own engine servicing, however I will say I've had more cases of mud-under-the-cap than I care to count on a variety of vehicles. Trust me if that was the problem it would've been fixed weeks ago and I wouldn't be here asking for help. Sorry if I sound like a d!@k right now but I'm frustrated with the whole situation considering this jeep is my only means of transporting my family of three; so needless to say I'm a little stressed at the potential of it dying after only having it for about six months and still making payments to the used lot. I would save us all alot of time and take it to a dealership but we all know how expensive and time consuming that can be and your stuck without your vic for who knows how long.

Zachariah Taylor

As for your first question, it's the Laredo 4.0L Inline6. And there are other places for the coolant to go than thought the head to mix with the oil, however I've noticed no major leaks to account for the loss, leading me to believe it's happening OTR at higher pressures.
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97grand4.0

Couple suggestions. Get a radiator pressure tester, pressurize the system, and look for leaks. Also there is no pcv valve on the inline 6. Get a fuel pressure tester and check for proper key on engine off pressure and also running pressure, and also shut it off and check the time it takes to leak down . Those specs are available on other threads I dont have them off the top.

rgr4475

Sorry my crystal ball is broken. You are a new member and I have no idea what your mechanical knowledge is. So we start simple and work our way from there.

dave1123

I may be out in left field, but the 97 4.0 had a distributor and spark plug wires, not a coil rail and digital cam sensor. Are you sure you don't have an engine swap going on here? The 99 and newer engines had the oil filter screwed to the side of the block. Where is yours? It should be screwed to an adapter near the oil pan. The newer engines also had motor mount bolt bosses in a different location.

One other possibility is it has a late model head on it and was changed over to the digital cam sensor. If so, all bets are off for being normal! I've owned a 97 ZJ and a 2000 WJ so I'm aware of what's going on with both.

The coolant loss may be from the water pump shaft seal. They are now designed with a small chamber that holds a tablespoon or so of leakage that is allowed to evaporate without showing a drip. I had this on my WJ. I could smell coolant, but couldn't find the leak until it got bad enough to sling off on startup. Also if the head HAS been changed, thread sealer MUST be used on the first head bolt on the driver's side. It's the only bolt that is threaded into the water jacket and coolant will seep up thru the threads into the first manifold stud and burn off. Look for deposits on the nut that holds the exhaust manifold on. A new head can also overstress old rings and make the engine burn oil and increase blowby. This happened with my 2000 with a new head after 150K miles. I'm currently using a quart in 500 miles and it's only showing smoke at idle.

This one has me intrigued and I will be following it closely.

stumpedagain

Stalling on most jeeps is due to CRANK SENSOR 99% OF THE TIME. misfires also are an indication of ignition timing related to CAP and Rotor as well as plug wires shorting on the block somewhere. On new engines 4.7 there is no rotor or wires, cpm does it all and when the crank sensor gets a little tired things get weird, won't get crank code but you will get misfires.

dave1123

I wonder where the OP went....He must not have liked our info.