5spdfrk

To begin, I have 1997 Jeep Cherokee 4.0 and haven't changed or replaced anything recently.

So my issues seemed to start last night on my way to the gym. My jeep felt like it was down on power as I was pulling out of my neighborhood. When I got to the first stop sign, it was idling a little rough. By the time I got to the gym, no issues were present. Leaving the gym, everything was fine, until I pulled into my neighborhood and it was trying to stall on me. I kept the RPMs high and quickly pulled into my driveway. At this point, the idle was really rough and the engine was making a knocking noise and starting to smoke. I shut it off and popped the hood. Couldn't quite tell where the smoke was coming from, but it appeared to be coming from the right headlight area and the intake manifold area. It doesn't smell like coolant, oil level is fine and it looks and smells normal too. Don't think any coolant is mixing in there, however, the coolant reservoir was basically empty. Didn't have time to fool with it last night, so I waited until today to check some more things.

Checked all the spark plugs today and while they could stand to be replaced, they were in typical shape. No fluids on the ground after sitting overnight and the oil level, look and smell was the same as last night. I scanned the computer and there weren't any current or pending codes. Started it up and listened to see if I could hear or see anything. Nothing was out of the norm. Decided to take it for a spin around the block to see how she drove. It still felt down on power and was overall fine until I was pulling back into my driveway at which point it completely stalled out. After manhandling it back into the driveway, I tried to start it, but all it did was turn over. Decided to give it some gas, tried again and it cranked right up. Let it idle for a couple minutes and it was rough. I gave it a little gas and the RPMs would drop really slowly. It began smoking again but not knocking, so I shut it off and popped the hood to look around. Smoke again was coming from the right headlight area and the intake manifold area. It started to pour down and get dark outside, so I have to let it sit another day.

Before throwing money at it and replacing random parts, is there anything I should start with or look at further to narrow down my issues? From what I've read on the forums, it could be related to anything from the catalytic converter to the throttle body. Any help is appreciated!

Firestorm500

Sounds like a cracked head and/or blown head gasket.

Further hands-on diagnosis is needed before teardown.

andrewmp6

Sounds like the head or maybe head gasket.Do a compression test on it that will tell you real fast if you have problems inside which sounds like you do.

anteb

+1. A compression test might be needed. Did it on a pickup I was going to purchase once and I'm glad I did. Keep us posted.

5spdfrk

Bought a compression tester today, plan on testing tonight. I'll post the results when I find out.

madmanmarty

Then drain your oil and take a look at it while it's draining.
You will be able to see if there is any coolant in the oil.

toasterknight

That's not a good indicator anymore it takes a lot of water for it to be noticeable in modern oil.

5spdfrk

Had some friends over last night, so I had some extra hands and eyes to help. Cranked it up to get it to operating temperature for the compression check and it runs fairly well until it starts to heat up. Then it would run very rough and start smoking. We got some flashlights in the engine bay and narrowed down the smoke coming from between the valve cover and head. Looks like the valve cover gasket isn't properly sealing. There's a fair amount of oil and gunk around the gasket, so it's possible that once the engine heats up and everything expands that the gasket is no longer able to create a seal. This might also explain the rough idle. Went ahead with the compression check while I had some help and here are the results.

Cyl 1 | 160
Cyl 2 | 163
Cyl 3 | 170
Cyl 4 | 164
Cyl 5 | 162
Cyl 6 | 160

I was very pleased with the results and relieved that it doesn't appear to be a head gasket issue. I plan to get a new valve cover gasket and go ahead and put in new plugs, wires, distributor cap and rotor while I'm in there. Hopefully this resolves my issues.

Firestorm500

I don't see how a leaky valve cover gasket could cause a rough idle, or all the other things you are experiencing.

I hope you can fix it relatively cheaply.

dans98xj

check the cat too. It could be clogged or the insides broke and are moving around. I had a problem similar to this changed the cat all is better now.

quneur

A leak down test will give better results. I wouldn't discount a cracked head or head gasket based upon a compression test. There are several tests out there besides a leak down test like testing combustion gases in coolant or mailing in a sample of oil to be tested.

andrewmp6

The only problem with a leak down test is most people don't have a air compressor at home.