Hey guys, been a while.

Since I swapped out the ignition switch this truck hasn't let me down once. Occasionally it won't start on the first try, but it always starts on the second. This happens after I drive it a while, shut it off, then try to start it about 5-10 minutes later.

I have been driving with the check engine light on for months now. EGR is the code. I have vacuum plugged the EGR and the EGR solenoid outlet.

Problem is that when I hook up the EGR vacuum line the truck suddenly has no power and spews black smoke. I stopped to check the wastegate and it is very hard to push down, indicating proper vacuum. As soon as I remove the vacuum line she starts running fine again.

I know the front solenoid is the Boost control, but the second one seems to be an intermediary between the EGR solenoid and the Boost solenoid. Also, there is a device running off the EGR solenoid outlet mounted up on the firewall.

You guys know anything about these three devices or what they control?

Any idea how to solve this problem without throwing lots of money at it?

 

You can't plug those off on a OBD-II truck like you can on OBD-I or you will code especially in EGR equipped trucks Vin S 8th digit or those oddball K2500s with EGR.

Only way to "overcome EGR codes it to reflash your PCM to a F truck set up, or plug the EGR port wither freeze plug in center of EGR "tower" under the upper intake, F engine gasket set that blocks port on lower intake or a .050" or so thisck shimstock between the EGR valve and upper intake.

This allows the PCM to be able to sense the change in system vac pressure for all 3 solenoids via the fire wall baro sensor and how PCM know the EGR system is still working.

Plug off and the PCM won't see the change to vac system pressure as EGR gets the vent command during EGR regulation and codes as EGR problem.

Of course you do know EGR is one of those things that can get you in trouble with "green police" so do what you think is best.

On a side note on S engined /L56 trucks there is a round "crush gasket" in center tower between upper and lower intake supposed to be 1 time use or it can leak EGR gasses full time, they also some times rot away and leak, would be worth your while to replace that also.

 

What is the middle solenoid's function?

You have the boost solenoid, X, and then the EGR solenoid (which routes up to the sensor on the firewall).

What is X and it's function?

 

Going to replace the white and red dot EGR solenoids. First two parts I am going to throw at it.

 

Update:

Original problem: When the EGR tube is connected to the red dot EGR solenoid the truck exhibits power loss and rolling black smoke. Idle okay and clean. SES light and 2-3 EGR codes.

Solution 1: Replaced both red and white dot EGR solenoids and hooked the EGR back up.

Result: Power loss, black smoke on acceleration

Notes: With everything connected the red dot EGR solenoid was simply unplugged. The engine ran at full power with no rolling black smoke.

Solution 2: [Anyone care to fill this in?]

 

1. Wastegate Solenoid
2. EGR Solenoid
3. EGR Vent Solenoid

They are not interchangable and vacuum lines must be hooked up properly for it all to function properly.

Without knowing the exact DTC(s), we can only guess..

FWIW, here DTC 78.. Although for OBD1 models, its largely applicable to OBD2 models also..

 

Im sorry, but the only egr problem you should be dealing with on these engines is how to remove it/bypass it without having a permanent check engine light. Recirculating hot soot is a terrible idea every time, works great on gas motors though.