Alrighty...my father-in-law's '97 Stratus Sedan (2.4L DOHC) was overheating and leaking oil. We got it into my shop and started into the head thinking the head gasket may be the problem. Nope...cracked head. (...all of this is covered in another thread...)

So we take the bad head off, find a good condition used head, had it machined and rebuilt and we slapped it on this weekend. After reassembly (which takes a while), it cranked right up, but it doesn't idle AT ALL. Above 1200 RPM it is smooth and runs great, but when it falls under 1200, it is really rough. Feels like it's missing. Just horrible...and it will die if you don't give it the gas again.

Our thoughts were 1 of 2 things: 1) Vacuum leak (oops, I forgot to connect...) or 2) Cam sensor/O2 sensor. Anything else we should look into? Thanks, guys...

 

100 to 1 your cams are out of time. To know for sure if they are properly timed, you need a straight edge across all 4 marks if they are lined up that is your problem. One of them is probably off a tooth. Almost idles like it has a bad egr valve. You can check the marks without having to take the whole thing back apart again, just take that upper cover off.

 

Arghhh...that upper cover is fun to take off.

Rick did the timing...and it was straight across with a straight edge, but I think they were right next to each other, but too high. Does that make any sense? It looked to me like the marks were on the upper part of the middle of the sprocket...man I can't explain anything without my hands!!!

He thinks the block is cracked now. Would that also explain it? Seems to me that if the block were cracked that it wouldn't run so good at upper RPMs. But what do I know? There was a lot of water leakage when he got it home...[&:]

 

I'm not a historian of these particular engines, but you don’t just crack a block, unless it was deliberately beat to death, or the motor has a history showing a design flaw. I doubt you need to look down that road. (Is the 2.4 in your sedan the Mitsu engine?)

The motor ran fine (except overheat and leak) prior to tear down, so the problem is most likely in the reassembly somewhere.
Cam timing is definitely one area, but with smooth operation at just above idle, I kinda feel that may not be the case. Vacuum leaks are most obvious an low RPM, and I'd bet dollars to doughnuts that you got a hose crossed there somewhere... Does the car still have the hose diagram under the hood?

I'm not much help beyond that, so hopefully others will step in and help out more...

Vince

 

I definitely agree, the engine would have to have been baked very bad to crack the block, and if it were cracked I would think that you would get a lot of pressure in the cooling system. Check the cam timing, check for vacuum leaks. Basically recheck everything.

 

Hope you don't mind me piggy-backing your post. I have a similar problem and looking for help determining the cause. My car was having a problem overheating and one day while I was driving down the road, it just lost acceleration. It did not smoke or anything like that - just when I was pressing the gas, the speed was declining. Did a compression test and it measured lower than I know it should. Is that a blown gasket or cracked header? Any direction would be appreciated.

 

First thing to check if it's a 2.4 is the head gasket. As far as the other guy and the cracked block, I dout it, these blocks on the Chysler 2.4's are pretty bullet proof.

 

thanks. it had a little water in the place where the spark plugs go if that helps make any diagnosis, but i will check the gasket

 

...there was also a huge water spill when he got home. When the motor is running, it holds water and doesn't overheat, but when you cut it off the water gushes out. Would this be the block?

As far as the heat goes, it was driven a couple of miles at full overheat before we tore it down...[&o]

 

Its a very good possibility that the block may be cracked, also its a possibility that the used head you got is bad....