What could have happened/Follow-up

You shouldn't start a new thread every time you post. I try to help out lots of folks with Jeeps in different places on the WWW and Usenet and it can be difficult to remember who is who or what is what.

So let's start over shall we.

What is the year and model and engine of the Jeep? Different years have different sensors and things such as EGR valves.

That sensor you just changed 'is' a temperature sensor, but for the gauge I believe if it is at the back top corner of the head with maybe a purple wire feeding it.

What were the symptoms 'before' the head gasket change? Were they similar? You could still be chasing something there and the blown gasket was just a coincidence.

Or something isn't plugged in right or is missing a connection. Did the O2 sensor down on the exhaust get plugged back in?

Did your spark plug wires get put back on in the right order, that is a sneaky one.

If it was a vacuum leak, the rpm would be very high.

I sure appears heat related at this point, but....

The TPS 'connection' is a notorious failure point. Sure sounds like yours has failed big time. A clean with a spray electronic contact cleaner or even WD40 can do that connection wonders or if it is already crapped out like it sounds, a new harness plug is called for. This could be a totally unrelated to the head gasket change failure.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > Oppps..OK first a correction..The sensor that was broken was one

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d gasket change failure.

Hello Mike..Thanks again for the quick detailed reply..I highlighted just the main things in your reply that may help with my trouble.. Mine is a 1994 Cherokee with an inline 4.0 engine. The TPS code is a completely unrelated item than the head gasket as the Jeep has shown that TPS code now for 2 years. About two years ago the right motor mount on my Jeep broke on the engine block side and the engine dropped down and the only thing that kept it from falling real far was that the bottom of the disributor came to rest on the part of the motor mount still sticking off the side...Soon after that the TPS code troubles appeared...(It may be totally unrelated to the motor mount break but I figure I`d mention it.) .What will happen is that the Jeep will drive totally fine until the check engine light comes on and then it begins to have the rough idle, hesitation etc...The odd thing is that if I get on the highway quickly I can drive 75 miles and the check engine light will never come on..But the first exit I go off and stop at a light or whatever and it pops on..If I`m driving stop and go in the city the check engine light will pop on after 10-15 minutes..I changed the TPS twice with ones from the local salvage yard and it didn`t help and now I`ve bought 2 new ones..Still no help..I am planning on giving everything a complete cleaning with contact cleaner tomorrow after work and will consider changing the plug on the TPS..It just seems odd that nothing shows up untill the engine reaches a specific temp OR if I stop and turn the Jeep off even after driving just 5 minutes as soon as I start it back up from there the codes back...Now like I mentioned that has been happening for 2 years and I have just come to accept it as one of the Jeeps quirks as this check engine thing didn`t make it undriveable it just a tad more rough at times. However since the head gasket replacement this check engine/TPS code quirk has become a lot worse and the Jeep almost becomes undriveable. Before the check light comes on it drives fine and smooth but something which occured during the head gasket change in combination with the TPS code makes that situation worse..If I can track down the cause of the TPS code constantly reappearing I`d be fine because aside from that the head gasket change seems to have gone fine. Or not..What do I know?...LOL :-)

gasket change failure.

You could be describing a connection that fails under heat load. How is the ground strap from the back of the engine up to the firewall?

Our 4.0 acted something like yours and got progressively worse. Half drove me nuts. It turned out to be a rotted pin on the coil's power connection. A real sneaky SOB because it is buried under the coil out of sight until you remove the coil.

You don't have an EGR valve that can give those kind of symptoms.

When was the last time the gas filter got changed? Our Cherokee had one on the driver's side frame rail in front of the gas tank.

How about the distributor cap and rotor. Those get overlooked, but a carbon track inside a distributor cap can act up like that. That would normally act worse in the rain though. Opening it up and shining a strong light inside can usually ID any spider web like marks inside. They can be white even.

There are a few ideas for you.

Mike

"Mike Roma You could be describing a connection that fails under heat load. How is the ground strap from the back of the engine up to the firewall?

Our 4.0 acted something like yours and got progressively worse. Half drove me nuts. It turned out to be a rotted pin on the coil's power connection. A real sneaky SOB because it is buried under the coil out of sight until you remove the coil.

You don't have an EGR valve that can give those kind of symptoms.

When was the last time the gas filter got changed? Our Cherokee had one on the driver's side frame rail in front of the gas tank.

How about the distributor cap and rotor. Those get overlooked, but a carbon track inside a distributor cap can act up like that. That would normally act worse in the rain though. Opening it up and shining a strong light inside can usually ID any spider web like marks inside. They can be white even. ______________________________________________________

Very strange; the problem shows up at the exact time an electric radiator fan would turn on for increased air flow. Or when a thermostat butterfly would open wider for increased coolant flow. Or when a thermostat is missing and the engine finally warms up to closed-loop mode.

My first guess is a defective ignition module. Intermittent and temperature-related; an old familiar story. A defective CTS might go nuts at a certain temperature.

An oxygen sensor wire pinched under the valve cover could make the car run rough when it switches to closed-loop mode.

A reappearing TPS code is mentioned, but the actual code number is not given. Is it possible that it is not the TPS code?

Good luck with this. Please post back if you find the cause.

Rodan.

The only code that ever turns up is a code 24 which according to my Haynes Manual just says Throttle Postiton Sensor. (Or TPS sensor circuit). But appearently the TPS isn`t the problem as that has been replaced a number of times. I will try a number of the ideas mentioned and look for hidden bad wires or plugs. As I mentioned the Jeep drives fine untill that Check Engine light pops on and then it runs roughly but it only seems to come on after the engine warms up to a certain point. On a related note although this code still appears and the Jeep runs a bit rougher when it does it no longer is the horrible undriveable manner it was the day I changed the head gasket or the following morning. I`m thinking perhaps having the fuel lines disconnected caused some sort of air problem which had to work its way out in the first 5 miles or so of driving and the TPS code made the matter worse?..Thanks again for all your guys knowledge and input. :-)