Where exactly is my tach wire?

[User_name]

@someotherguy If you zoom in, you can see the esc module directly on top of the egr solenoid. And my truck has the one wire o2 sensor

 

[someotherguy]

@someotherguy If you zoom in, you can see the esc module directly on top of the egr solenoid. And my truck has the one wire o2 sensor

Yep. Exactly as I suspected, and you described. Your NV4500-equipped truck has a regular ECM with the external ESC module.

Richard

 

[User_name]

@someotherguy yes sir, didn't know the tbi engines even had an internal esc module

 

[PlayingWithTBI]

There are some differences in engine management when you have the manual transmission. If you can post a pic of that area of the engine, it would be helpful. For example light duty trucks with automatics got the 3-wire heated O2 sensor in '94, but my '95 3500HD with NV4500 had a 1-wire non-heated O2, original. With the manual trans, your truck may have the old style ECM, instead of the PCM with built-in ESC module. The automatic trucks got away from the external ESC in '93 for the most part.

I forgot, he was running a stick shift, I was thinking about the '7427 PCM, my bad.

 

[someotherguy]

@someotherguy yes sir, didn't know the tbi engines even had an internal esc module

Yep. The PCM-equipped trucks have the same bracket but hold only the EGR solenoid on the back side. Blank on the section that would have housed the ESC. Detail shot from the teardown on my '94 C2500LD (5.7/4L60E) before intake gasket replacement. (the vacuum tee you see at the PCV connection on the TBI is not OEM; it's where I added the line to the vacuum gauge I installed.)

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Richard

 

[PlayingWithTBI]

The PCM-equipped trucks have the same bracket but hold only the EGR solenoid on the back side. Blank on the section that would have housed the ESC. Detail shot from the teardown on my '94 C2500LD (5.7/4L60E) before intake gasket replacement.

And, it looks like, in later years, GM moved the MAP sensor from that bracket to behind the EGR valve too.

 

[someotherguy]

And, it looks like, in later years, GM moved the MAP sensor from that bracket to behind the EGR valve too.

Yep. It got its own bracket. Many small changes throughout the years. 1994 was first to have the evap purge solenoid you see in the pic, too (next to thermostat housing.)

Richard

 

[User_name]

Even with all its faults, and the fact that this truck has made me think about doing drugs, I still love it. This truck is definitely a labor of love.

 

[Schurkey]

Do these tbi engines use normal sbc intake bolts? I was looking to get some new ones (probably the allen head ones) since I'll be cleaning everything else up

Not on my '88.

The two on the left rear have studs that stick up from the bolt heads, that hold the bracket that mounts the throttle, cruise, and TV cable.

There's a studded bolt on the right front, and I think there's one on the right rear. I forget what--if anything--attaches to those.

(the vacuum tee you see at the PCV connection on the TBI is not OEM; it's where I added the line to the vacuum gauge I installed.)

You must be registered for see images attach

A vacuum gauge connected to the PCV hose is likely to show lower-than-true manifold vacuum, due to the "controlled vacuum leak" at the PCV valve. Might be OK for verifying the PCV valve, but not much good for diagnosing anything else.

 

[someotherguy]

A vacuum gauge connected to the PCV hose is likely to show lower-than-true manifold vacuum, due to the "controlled vacuum leak" at the PCV valve. Might be OK for verifying the PCV valve, but not much good for diagnosing anything else.

Baselined at around 18-19" hg at near sea level. Seemed pretty accurate to what I was expecting. Vacuum source being the port on the TBI for the PCV.

Richard