Can Heat Soak Happen at High and Low Temps?

I'm experiencing the symptoms of heat soak at different temperatures. I can start my '99 Cherokee XJ in the mornings on a cold or hot day and I'll get a sputtering in the engine response when I pull out of my drive (It goes away after driving for a couple minutes.). When I let the engine warm up for a bit longer before pulling out of the driveway, the sputtering can be less prevalent.

Then, I can also get heat soak in the more typical scenario, like when the engine has been running for a long while and then I turn it off and sit for a bit and then start it back up. It can also occur if the engine is idling for a long period of time and the engine heats up.

My question is, can I have actual heat soak in the morning before the engine has gotten up to temp, or is that a sign of something else, like a bad fuel pump?

I'm not sure if I have two problems or one.

No, with out heat you can’t have “heat soak” with out heat. How ever you can have what you are experiencing from air in the fuel system from vapor lock from the heat prior. After cool down air and pressure drops, air is getting in to the fuel rail which will cause the symptoms. When cool. Insulate the fuel rail, and the exhaust manifold under it, check the fuel line and replace if needed with injection rated line. It maybe sucking air in the the fuel system on cool down. It could also be a fuel pump on its way out. Pressure is your friend in a fuel injection system. Make sure you hold pressure to reduce boiling and lose of pressure.
CH

COdoubleoughtxj said:

No, with out heat you can’t have “heat soak” with out heat. How ever you can have what you are experiencing from air in the fuel system from vapor lock from the heat prior. After cool down air and pressure drops, air is getting in to the fuel rail which will cause the symptoms. When cool. Insulate the fuel rail, and the exhaust manifold under it, check the fuel line and replace if needed with injection rated line. It maybe sucking air in the the fuel system on cool down. It could also be a fuel pump on its way out. Pressure is your friend in a fuel injection system. Make sure you hold pressure to reduce boiling and lose of pressure.
CH

Click to expand...

Thank you for the very helpful reply. Your info should get me going towards a fix without a lot of guess work. I appreciate it!

Sent from my SM-G950U1 using Tapatalk

Your very welcome TexJ99, been there done this, VBG.
CH

I came across this helpful video (link below) from "JeepSolid" on YouTube and it demonstrates how to properly test your fuel system pressure. I figured it could be helpful to anyone that views this post in the future.

https://www.youtube.com/watch?v=8tXadgKF6oA