1989 xj difficulty starting in the cold

I have a 1989 Xj 6 cylinder that has difficulty starting on cold mornings sometimes. The battery is turning the engine over as it normally would but it doesn't start. It just cranks and cranks. I can hear the fuel pump kicking over like normal before I crank it over. It is like it is not getting a spark. I'm thinking its a sensor of some type that needs replaced that is preventing it from sparking. When the weather is warm it fires right up. When it doesn't start and I put the hood up and the sun shines on the motor for a bit and it warms up it fires right up. It has been this way for a few years and I just mainly drive it in the summer as a result.

Also, sometimes when the engine is warm and I start it up the engine races (usually when I stop at a store or something and turn the engine on after its off for a few minutes). I have to turn it off and turn it on again and it usually is back to normal. Sometimes it takes a couple tries before the engine is runs at a normal rpm. Not sure if these two symptoms are related or not but figured I'd mention it.

I figured I'd see if there were any suggestions before starting to switch out sensors, as many of them are pricy. Any suggestions on where to start would be much appreciated.

Hmmm... Check your Intake Air Control valve on the TB. You can remove it and the air intake as well and see if there's any carbon buildup on the pintel or in the boss.

You can test many of the sensors.

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Another good Renix era write up.

Cruiser54's mostly Renix Tips

http://www.naxja.org/forum/attachment.php?attachmentid=5116&d=1414073288

Test the air temp sensor on manifold.

Note from DJ
Please don’t start throwing new parts on in hopes of fixing your Jeep!
Quality control is poor in a lot of replacement parts now days; some are even defective right out of the new box.
Don’t be afraid to ask questions and keep every buddy posted as to where you’re at.
There are many people on hear that will be glad to supply you with their knowledge.
You have been given two excellent links for information on trouble shooting your Jeep; book mark both, they are loaded with information.
You need patience and a VOM meter to work on a Renix vintage Jeep.
You are going to need a spray can of throttle body cleaner in order to complete both of the suggested tasks.
A word of caution when removing, cleaning and replacing the Intake Manifold Air Temperature Sensor be careful with it; the only place to get a replacement on is at the junk yard; there are no new ones available!
Here is the link to a past post that has a lot of information on the Renix start up’s
Another No Spark, No Start, by BlackRock on 5-07-2012
http://www.naxja.org/forum/showthread.php?t=1083818
See Post #4 by 8Mud

Thank you for the suggestions. I'll get going on it this weekend to see if I can get it figured out. Thanks again!

FLAGXJ said:

Thank you for the suggestions. I'll get going on it this weekend to see if I can get it figured out. Thanks again!

Click to expand...

Do Tips 1,3,4, and 5 before doing anything else.

Clean your throttle body and make sure your intake bolts are snug.

How old are the plugs, wires, cap and rotor?

After you've done all that, when you come down to buy my doors, I'll hook it up to the factory DRB tester for you........

That sounds good!

Do the "ground work" stuff first.

Just a side thought, but how many CCA (cold cranking amps) does our battery have?