1995 Tahoe questions

I have 2 what is it questions.

There is a 2 wire plug I believe they were green and black that was hanging down by the fuse box. I did not see where to plug it into. I have no idea how long it's been off or where it goes. I will post a couple pics.

On the firewall above the fuse box there is something that is vacuum operated. I'll show pics of that also.

When you start the Tahoe the rod that activates the turbo still moves. I have very good vacuum.

If you plug in directly to the turbo, it holds tight.

I am sealing the valve covers, changing injectors, testing glow plugs, changing to F intakes and servicing. Don't let the under hood PMD bother you. It's the spare and when I am done, it will be in the bumper also.

Any ideas would be appreciated.

Thanks

 

The piece on the firewall is a Map sensor, the plug with the green and black wire is usually for the air conditioning like for a low or high pressure switch or the compressor clutch.

 

Hey get your "spare" out the engine bay also I lost one there just sitting there, it had 3 starts on it from new I was surprised when it was bad from just sitting in engine bay, maybe just bad from Stanadyne but since then I don't keep spare s under hood either.

OBD-I S&F use the firewall sensor for baro and boost second sensor on intake they are VERY SIMILAR in appearance but are index keyed differently, make sure when you go to a part store you get the correct sensor for intended purposes.

OBD-II S uses firewall baro and intake MAP still, F OBD-II only uses the intake MAP sensor for baro at start stores reading then shifts to boost reading only thru the MAP

Those would be correct colors on your 2 wire plug for AC compressor but your AC is on opposite side, on your year Tahoe does the plug reach the pass side ?

In the other photos blue wire with single brown plugs, those look like the connectors for your glows are you running without glows that side or just disconnected now in prep to swap over to the F intake ?

 

Is there a good place to get the part numbers for the EGR/Baro Sensor - May be Delphi PS10082

The 3 Solenoids EGR SOL VLV (VENT), EGR SOL VLV (PWM), TURBO SOL VLV

Maybe these ACDelco 214-637 GM Original Equipment Turbocharger Wastegate Solenoid,


Delphi PS10082 Barometric Pressure Sensor


ACDelco 213-1520 GM Original Equipment Manifold Absolute Pressure Sensor


I still haven't verified these are the exact parts I need.

I could not find a cross to see if the Delphi and the ACDelco numbers crossed. I seem to be struggling with this for no good reason. I've got over 2 hours in it now. I need to get ordered so I can have the parts to put stuff back together

 

I'm confused if going to F config why are you concerned with EGR related solenoids ?

When I get home I'll pop hood to see if I can read pns on my solenoids

 

Just disconnected for now. I already checked the glows on that side of the engine. Easiest part of the whole job. LOL.

Right next to the EGR/Baro sensor is the dual lift pump relay upgrade. I'm adding a fused toggle switch to run the lift pump for bleeding and diagnostics. I always just pulled the fuse and jumpered it there. But I have found a permanently mounted toggle is very handy

 

I heard from somebody that you still need the baro and the Turbo Solenoid VLV

 

WG solenoid still needs to be there unless going with a non WG turbo,

Once you reflash/chip the PCM to F it should not look for the EGR related inputs, I have mine connected still as I don't believe in leaving wiring un-terminated, as it completes ground loops, and also assists with "noise" on the control signal wiring.

Are yours missing now ? or are you suspect they are bad causing error codes ?

 

I suspect either the Baro or the WG solenoid is bad. I have to double check my vacuum but I think it was 26 hg or above - Is that the magic number for the vac to read and the turbo work?

With the engine off you can easily move the rod back and forth. With the engine running you can move it just the same - I thought I remembered that with the engine running the rod should be hard to move.

If I bypass the WG solenoid and hook the vacuum pump directly to the waste gate the rod is hard to move, like what I expected.

So I am thinking that indicates the WG solenoid is bad or it is not being told to opperate

12569240 is the EGR Baro sensor - verified

The waste gate solenoid is GM 1997255 - verified

The EGR solenoids - vacuum regulator valves EGR SOL VLV (vent) & EGR SOL VLV (PWM) have 2 different numbers, but I do not know which is which.

1997225 & 1997226

 

22-26 is full vac, measure 1st at the input to the vac solenoid group, to verify full vac, then at outlet of each solenoid yours being a OBD-I "dumb PCM" you could just go straight to the WG actuator and keep full vac applied for full boost all time, or go with a TM, the OBD-I PCM does not monitor vac system like OBD-II does

Remember for the 6.5 boost control vac is applied 100% of time unless PCM sees neeed for less boost then it vents it allows a little less voltage to the WG solenoid allowing WG to open for less drive gas to the turbos drive wheel and ergo less boost generated.

This is why much easier for OBD-I guys to convert to F they just plug off the solenoids not needed and let WG solenoid control vac to the actuator "can".

If your vac from the pump is good then plumb to the WG solenoid only, if solenoid is good you will have same vac out of the solenoid as you have to the solenoid, if not that is bad solenoid or the power to the solenoid isn't present have you checked for that ?

I was going to post the vac system diagram but apparently I don't have it on this computer.