Cold Air Advance solenoid
 

I am new to diesels.I bought this C3500 truck and it runs really weak no power. Its 1993 C3500 Automatic transmission with 140k on it.
1st to 2nd shifts really hard and the 3rd shifts really early and 4th the same. Sometimes i lose 4th. All i have to do is turn off the truck and start it again and i have overdrive.
I found that the Cold air Advance solenoid was disconnected. Why would someone do this?
From what i understand it will run terrible without the sensor. Is that right? No power, Random Shifts, And lose overdrive. I jumped it out and truck ran strong. I am just looking for conformation that this is my problems. Also the transmission fluid was burnt but very little
residue in the magnet or pan so i think the transmission is fine. I have looked at many forums and have gotten conflicting statements.
Does the cold air advance solenoid affect shifting and power disconnected? Also will it make overdrive drop out at times? I saw the term limp mode a few times. Is this what its doing?

cold air solenoid
 

I really need some assistance. I just dont know diesels yet. I will though.

surely someone knows.

It is the shift solenoids inside the transmission more than likely the transmission is on the way out that cold air advance you are talking about is really a high idle for when the engine is cold it steps up the idle when you first start up, so you will want to find a reputable transmission repair shop and get it overhauled before it goes out.

And limp mode is on electronic injected 6.5 92-93 are mechanical injection so this doesn't apply to your model.

Ty so much will be replacing solenoids asap~

I just changed my cold advance solenoid. Still dont know why but its changing gears
and running great with this changed. Thanks for the help. I can only assume that this has been changed into a 94 wiring harness. Only thing i can reason. BUT its fixed running
great.

Engine back to acting up. Replaced inner wiring harness will shift hard 1-2 3 shifts fast and no 4th.

Only way to fix it is turn it off and restart the truck. I do have the cold air solenoid jumpered out. It does help it from acting up so much.

Any ideas?

Ok cleaned all grounds and adjusted the TPS sensor. FIXED