I finished up replacing my head gasket today and now I have a rough idle. Here is a list of parts I replaced. Head gasket, head bolts, valve cover gasket, intake/exhaust manifold gasket, throttle body gasket, left and right motor mounts, coil, spark plugs, plug wires, oil filter adapter oring, oil filter, oil and water pump.

When the head gasket blew, I was on the highway doing about 70. The CEL came on amd I lost power. I pulled over and steam was coming out of the intake. When I tore everything down, there was no coolant in the oil and no oil in the coolant. I think I shut it down quick enough. I also checked the head and block with a straight edge and no visible damage was done other than the blown gasket.

Ok, now to the problem. I finished putting it all back together this afternoon, started it up and it has a rough idle. I let it run for over an hour and it never cleared up. I went around the block twice and it wants to die when I let off the accelerator at stop signs. I then took it on the highway. It seemed to run good at speed. No CEL. Just a rough idle. Then after coming out of a u turn, I got on it a little. After I settled into 55mph and OD, it started running rough and the CEL came on. I ran over to Oreilleys and it showed #2 & #4 misfire.

Now before you say anything, I've already checked for vacuum leaks and cannot find any. I've put my old plug wires back on thinking a new one is bad.

I cannot figure out why it is idleing rough now. I cleared the misfire code and it hasn't come back on.

Does anyone have any clue what it might be? It ran perfect before the head gasket blew. Idled smooth and didn't have a single tick.

What are the symptoms of a bad IAC motor?

Any help is appreciated. My XJ has been down for two weeks now. I'm ready to go offroading again.

 

Recheck the firing order? That's the first thing that comes to my mind.

 

Done that several times.

 

Wanting to die when you let off the gas could be a sticky IAC or a bad TPS. You can pull the IAC and clean it up. TPS you can check the voltage with a DVM:
Key on, center connector, should be a few millivolts with the throttle closed and rise smoothly to about 4.8V as you open the throttle by hand.
Don't discount a bad new plug either, I've had it happen more often than you'd think.

 

Head did not get sent out and checked ?

 

did you have any gunk in your intake that you might've cleaned out? maybe some junk got stuck on the injector? happened to me after doing my freeze plugs

 

I cleaned the IAC a couple of weeks ago. I pulled it off last night and checked it again though.

I checked the head with a straight edge and feeler gauges.

 

TPS ranges from .80 to 3.79.

 

Junk. OBD-II is 0.2 to 0.5 shut, 4.5 to 4.9 open.

 

check CPS or Fuel injectors

 

Well, my head is warped. Did a compression test and #2 & #4 only had 30 pounds. Pulled the head off and checked again. I guess I missed it the first time. Oh well, lesson learned. I got another head lined up already.

 

Let a machine shop take care of it ....old warped head can be saved

 

Yeah, I know it can be saved, but a buddy of mine has one with 1000 miles on it and he's giving it to me.