Hey Scotty, I have a 1995 GMC Suburban LTE C1500 with 253,000 miles, and it runs like a champ until the engine bay gets damp. As in if the engine is washed down with water (which I know is not ideal),…

e4g67

Hey Scotty, I have a 1995 GMC Suburban LTE C1500 with 253,000 miles, and it runs like a champ until the engine bay gets damp. As in if the engine is washed down with water (which I know is not ideal), or if there is an extremely foggy/damp day and moisture builds in the engine bay. What will happen is that I will get a check engine light on the dash, the engine idle will increase from its usual 750 rpm to @ 1000 rpm or maybe a tad higher. The transmission shift points will only happen at much higher engine rpms when this issue occurs. In other words, instead of shifting to 2nd at a moderate speed and rpm range, the shift will not happen until much closer to redline. All of the shift points will be at the top range of the speed for each gear and will not vary until the engine bay warms up enough to evaporate the moisture from whatever component is being affected. After the moisture has dried the operation of the transmission will be normal and the check engine light will go off. For what it is worth, the vehicle has the optional towing package from GMC. Also, I take very meticulous care of the vehicle. I'm thinking there is an electrical component that is causing this issue when it becomes damp. Any thoughts as to where I should begin looking for my gremlin? Thanks, Gene. BTW, you're awesome buddy!

Comments (1)
No. 1-1
Scotty Kilmer
Scotty Kilmer

Editor

so many electrical problems can do that, make your head spin. But on GMs, often bad ground wires do that. Get a wiring diagram and check all ground in the engine bay and transmission first.