I just replaced the head gasket and cylinder head on my 91 xj 4.0. when i start the engine now it races right up to 6000 rpms and has to be shut off immediately. it acts like the throttle is stuck wide open but it is not. i have tested the tps and it tests good. any ideas?

 

upon furthur inspection i found that the bottom of the intake manifold was hung up on something and so there was a rather large air leak. seated manifold correctly and idles perfectly fine now.

 

Good. I was going to say the vacuum line from your brake booster was disconnected or had a goodly leak.

 

Why did you replace the head btw?

 

cracks in cylinder head combustion chamber from previous over heating. replaced most of the cooling system and still runs hot and over heats on the highway(65+ mph) but will idle all day in 115 degree day without overheating. just have to baby it until the cooler weather gets here i guess.