What I have:

1994 Jeep Cherokee SE. The Jeep has about 154K miles and no engine mods to the 4.0L.

The Story:

A few weeks ago I took my brother out for an adventure sponsored by me and the Jeep. While adventuring I came across a run off creek in the trail.... I went way too fast through it. About 2/3 the way through the jeep died. Trying to start it, the starter seemed to... It would crank the motor then just slam to a stop. Soon the starter was turning the motor over and the Jeep started and ran. However, there was a knocking noise from the engine. Also it ran rough, it would die when going down hill or not under load for some time. But its a Jeep so it made it home!

The Issues:

I am most concerned about a knocking noise from the motor, it seems to be from the top of the motor. After not running for a few days, when started there wasn't any knocking for a brief moment, then there it was. Also the knocking increases with rpms, hit the throttle and it increases the knocking.

The Jeep also has a rough idle and idles very low. When I unplugged vacuum lines (PVC and random others) the idle seemed to return to normal.

Hard starts is another problem. It seemed I would have to crank on it quite a few times for it to start. It never did this before the adventure I sponsored.

What I've tried:

First I took the valve cover off. All the rockers were tight and appeared to be normal. I took each rocker and rod off one by one. Everything seemed good. I tightened them back down per Haynes specs (19 lbs.) and put the cover back on, still knocking. With the engine running, I unplugged each wire one by one to the spark plugs. The knocking continued.

I figured I may have inhaled some h2o and my plugs were pretty old so I replaced the plugs (.35 gap), wires, dsit. cap and rotor. It seemed to help with the starting but nothing else.

As far as the idle, I played with the vacuum lines and that was it. I thought an open vacuum line would make it idle low?? I can't find anything in the book about adjusting the idle, I assume this is because of the year and fuel injection.

Any idears??

 

I wanna say you just have the notorious 4.0 song playing (the knocking) and you killed one of the sensors when you crossed the creek. Videos are a huge help for us.

 

I hoped this worked and if it did, forgive my camera skills.

It didn't work.

Video is coming... eventually!

 

Here are a couple of videos.

The first is the engine knock. I used a crappy camera and was on the noisy side of the engine, but here it is:

http://www.youtube.com/watch?v=8LweN...ature=youtu.be

After running for a few the engine starts idling slower until it almost wants to die. If I unplug a vacuum hose, the engine returns to a better idle. I unplugged the PCV and the hose to the vacuum canister. Here's a link:

http://www.youtube.com/watch?v=XMrVe...ature=youtu.be