Weak engine brake on MXS Acert

06 Pete 379 mxs Acert
500,000 miles

Today I noticed when I use my engine brake on high it is weak and doesn't sound right. It will do it with the engine hot or cold. Sometimes it works good next time it is weak. When it works good I have 25-30 lbs boost.

It is a three stage and it does work low, med, and high. When it is acting up on high and I switch to low and med it changes cylinders like it should but when on all three you can tell something is wrong.

I don't have a cel light on or any fault codes. Am I looking at a electrical problem, such as a loose wire or bad solenoid, or could it be mechanical? I haven't had time to pull off valve covers but what are some things I can check under there? Other then the intermittent engine brake issue the engine sounds and runs good.

Thanks in advance.

 

Yes it is between full and add last I checked.

 

Update: I think I may have found my problem. I got time today to take off the valve covers and inspect the plugs. The very rear jake solenoid plug had parts of the plastic missing and had both connections open to each other.

I will add some photos. Luckily I had a spare plug in my side box cause I've had to replace a few Iva solenoid plugs as well. I think this winter I will get both harnesses and replace them.