1997 Sport with 114k. Tried everything. Starts up and idles great when it's cold. When the engine gets warm it idles very rough. Have to give it gas to keep it running. Also, hesitates with minor throttle, but only at speeds over 50mph. If you give it full throttle the hesitation goes away though. Replaced, plugs, wires, dist cap, both o2 sensors, and throttle position sensor. Anybody experience this? The only thing left i can think of is the crankshaft position sensor, could that be my issue?

 

iac its on your throttle body on the right side....try that first

 

tps has nothing to do with that it for your trans. g/l thow if its not your iac lol i just blew my front end so im feelin ya

 

Do you have a CEL at all? If you do, does it blink when you're driving? I would also check the intake air temp sensor or the coolant temp sensor.

 

No CEL. I will try the IAC tomorrow and see what happens. If the IAC was bad wouldn't it idle rough all the time, or no? It idles like a champ when it's cold, and it never hesitates on start up, fires up instantly, every time.

 

Even though i never got a CEL i decided to hook it up to the meter. It gave me code P1296, which refers to voltage going to the MAP sensor. It started to make sense that it was electrical, because my other problem is my fuel gauge not working at low RPM's, which i thought was unrelated. I tried a new MAP sensor, nothing. Runs exactly the same. Idles rough, and hiccups with slight acceleration, everything clears up, and fuel gauge works at high RPM too. I'm starting to think it must be a short in the system somewhere. Anyone else have this issue?

 

check for a vacume leak

 

Just checked, no vacuum leaks, but I think I might have found something. I found a plug that was tucked away, not plugged into anything. It comes up the main harness. There are 3 plugs coming out together, 1 goes to the AC drier, the other goes to something having to do with the vacuum system (I think) it's next to the drier with 2 vacuum lines coming out of it, and the other one I found. If the code says I'm not getting voltage to the map sensor I'm hoping I just have a rogue wire. Does anyone know what this could plug into. I will try to post pics tomorrow. If you need any other info, just ask.

 

I have a similar problem but I think I have a clogged cat.. I ordered one form summit and will install it tomorrow

 

I hate to rule anything out at this point, but I really think mine is electrical. I see why the guy sold it. The more I get into it, the more **** I find. I found out why I wasn't getting a CEL, the bastard took the bulb out. He was throwing parts at it and finally gave up. By the time I'm done it's going to have every sensor replaced. I just need to find out what that plug goes to, and see if there is any connection with this problem and the fuel gauge. I tested the rogue wire I found and it's hot, which leads me more to believe the joker that owned it before was messing with it and that's when his problems started.

 

Thanks splblackxj. It was the IAC. I pulled it out and noticed the throttle body was all carboned up. Removed the entire throttle body and all sensors. Cleaned up the IAC, put it all back together and its running great. I still get a 42 code that I cant trace. It doesn't trigger a CEL though. You ever experienced the fuel gauge issues? Mines starting to act up.

 

my jeep does the same thing. when it gets warm and i shut it off for 10 min and start it up again it idles really rough and coughs and chokes a bit. after about 2 min of that its fine. i was told it was the crankshaft position sensor. jeep is fine when its warm and i let it idle.

 

I have a 98 xj and it's doing the same thing. I use it as my dd and wheeling. Day to day it's fine no matter how much it runs, but as soon as I hit the trails it will warm up and it starts running ruff when I start it back up then it will clear. If i leave it running it won't do it at all. I'm like to know what you kind I'm going to check the IAC and see if it needs cleaning. I have never had any problems with the fuel gage though.

 

mine's a little different. I start my jeep, runs great, if i let it idle for a while, like ten minutes, it'll start to idle at around 1500, but rough. and it backfires a tiny bit. Not sure what's going on. sounds like a lean problem, and I know my throttle body gasket is broken, so i'm praying that this fixes it.

 

Yeah a leak around there can definitely cause that. Change that gasket, make sure you torque it down right, and you will probably be fine