Re: Plenum pull advice
 

The one behind the plenium had a wet oily film in it when you pull the hose. My guess is that there is a rubber diaphragm in there and the oil might cause problems and a false reading.

Dave

Re: Plenum pull advice
 

The one you are referring to, under the ECM (later moved to underside of plenum, forward of DIS Module) is an MDP Sensor, Manifold Differential Pressure. They look alike, but are not interchangeable. In fact, the harness plugs will not interchange, i.e. you cannot plug a MAP sensor at the MDP location nor an MDP sensor at the MAP location.

We stock both sensors. If you want to see them, go to the web store & search by the PN's.

You can tell them apart visually if you know what to look for.
http://i190.photobucket.com/albums/z...psd7ba8556.jpg

Re: Plenum pull advice
 

Jerry thank you, in your professional opinion Jerry should the oily map be changed out or should it be fine? Also is this normal to get oil up there or is this caused by another problem in the system? The engine has 80k great compression and no blow by.

Also thank you Jerry for gettin the fuel systems orings to my door so quickly.

Dave:handshak:

Re: Plenum pull advice
 

On page 6E3 A-4 of the 90 FSM it is called a "Vacuum Sensor" and feeds the "Secondary Port Throttle Valve Vacuum Sensor Signal" line to the ECM. I've never heard of one of these failing.

Re: Plenum pull advice
 

The oil you are seeing is normal, comes to the plenum via the PCV system when crankcase pressure is at its greatest.... WOT/high rpm. The LT5 unique PCV system with it's dual PCV valves was the result of crankcase pressure experience during development. After playing hard and being shut down for awhile, oil in the plenum will sometimes cause a puff of smoke on startup, due entirely to oil draining down the plenum runners.

I've never installed an oil catch can, but do think it is a good idea. Keeping oil out of the intake is always a good idea.

I wouldn't be concerned about the oily residue. It's only a problem if it collects in the hose and interferes with the vacuum sensing.

Re: Plenum pull advice
 

To keep the plenum from developing ice never bypass the TB.
Early engine development discovered in a catastrophic way
that ice can build then release into the heads. Depends on environmental conditions of course.

To "burp" the coolant simply leave the driver's side TB hose pointing up
as you fill the coolant reservoir. When you see a bit of coolant come out of the TB you're done. No blowing the LT5 needed. :p

Air Locked Water Pump
 

Add an Oil Catch Can. See LT5 Added Systems

Delete TB coolant and Plenum Pulls will even be simpler. See LT5 Eliminated Systems

Now for those that are skeered about refilling with coolant......there is a trick to make sure no air pockets in the water pump area (air locked water pump which is typical for an LT5 with a new coolant refill). See Filling With Coolant and the Air Locked Water Pump

Trouble is.......no amount of "burping by gravity" will get that air out of the air locked water pump (you can blow (with your own lungs) a pressure of 5 ft of water as a comparison to holding the TB hose only a few inches higher). You may get lucky and the water pump spin up a little water to start flushing air but usually that is not the case.

The problem is that the Water Pump cavity is above the outlet ports (red line in photo). Air gets stalled above the water line and the pump becomes air locked spinning the air with no water movement.

http://i287.photobucket.com/albums/l...830bc8f7e7.jpg

Re: Plenum pull advice
 

"scottfab"...Please, cite the source of your information about early LT5 development and TB ice being ingested into the engine.

Re: Plenum pull advice
 

Today was a bust Everything got in the way of the zr1. I hope tomorrow is better.

Dave

Re: Plenum pull advice
 

Dave,

Tomorrow is always a better day!!!

Jep