I have a 89 Cherokee laredo, And i hydrolocked the motor in about 4 feet of water =( The question is, ever since then, It runs at a REAL high idol, and when i un plug the map sensor the idol comes back down but the timeing is off, and it gets very hot to the point the exhaust pipe is glowing red, and its back fireing and theres alot of smoke, but when i plug it back in, it runs perfect but at a real high idol. Whats the problem??

 

Time for a new motor.

 

AHHHHH thats not what i wanted to hear =(

 

Hydro locked means you've probably done some serious damage to the rotating assembly. Start fresh...and stay out of the water!!

 

But Whats causing it to run so high. could a vacume line be undone somewhere?
If the motor is shot, ill probaly run it till it dies lol

 

remember jeeps are not submarines but we all think are jeeps are unstoppable

 

you say the engine runs perfectly fine with everything plugged in but only has a high idle??? If thats the case its probably a bad sensor. Which one i wouldnt know, but if the engine IS running with good power then its not a mechanical issue, its an electrical one.

The reason its runing so hot and rough and backfiring when you unplug the sensor is because its running way too rich and there is unburned gasoline in the exhaust headers. DO NOT DO THIS. Leave everything plugged in! lol

 

X2 sounds like a electrical problem or could be a major vacume leak.

 

If the engine runs good and the oil pressure is up, no knocking noise and excessive oil consumption your engine is GOOD.
Many people don't know what hydrolock really means. When an engine is hydrolocked the engine sucks so much water that the pistons cannot go all the way up beacause of the incompressibility of water. At this point the inertia of the crankshaft rotation forces the piston to go up and you break either a conrod or the head, engine stops turning immediately with one big KNOCK.
If you try to crank it= nothing, turn it by hand= nothing etc...
In 90% of the cases the water isn't enough and the engine stops turning because of wet spark plugs or water in the distributor, but when you crank it it turns.
So what probably has happened is that you either have a busted TPS or IAC, that notoriously are known to dislike water. Try to swap those first before you condemn the engine and don't listen to the swappologists that say your engine is shot.
Here is a pic of my hydrolocked suzuki sidekick engine.

 

If the engine got enough water in it to stop the motor the chances of having bent the rods or crankshaft are prety good. With the availablity of 4.0L motors at any JY for a low price, why keep an engine that has been hydrolocked?

 

A bent rod is still a rod. A bent crankshaft lasts 15 minutes.

 

If a rod was bent the compression ratio for that cylinder would be WAY low. Do a compression check on all six cylinders. They should all be within 10-15 percent of each other. That will end the speculation and tell you for sure if you damaged the motor.

 

try changing both of the sensors on the throttle body first. thats what normally causes a high idle

 

you might be able to take the entire motor apart and clean everything out and put it all back togeather

 

well you could stroke it if there isnt damage to the block like fantic showed you.

thats assuming you actually hydrolocked it, not just messed something up electrical.

otherwise go with FrankZ and find a new 4.0 in the junk yard with not a ton of miles.