I have a 85 TPI setup on a 87 version engine. The mechanic that put this together did not elongate the center bolt holes and the edges are all busted. My question is; will my cold start injector work with a 90-92 base intake manifold. I have the 85 ECM and the motor starts great with th CS injector. I'm trying to avoid elongating the holes on an early manifold and just using a late manifold for a perfect fit. Will the CS injector spray fuel into the combustion chamber with the 90-92 base intake manifold?

 

90-92 intake manifold doesn't have the cold start injector. I think the 87-88 do have the cold start injector.

 

That is correct, 89-92 does not have a CSI with the runners, but does the 89-92 base manifiold still have the provision for a CSI runner and will it allow fuel in the combustion chamber to start the engine. I'm thinking that the fuel travels through the EGR passages to the combustion chamber for start up. Is this true? I can get my hands on a 91 intake in great condition, 87-88's are hard to find.

 

I can't remember.

See if the seller can send you a pic of the underside of the manifold.

 

The base (lower) intake does work with the 86-86 cold start runners and injector. But you will have to drill and tap a hole in the front of the manifold for the cold start injector sensor. I currently have a 90 engine, heads and all with the 90 lower intake drilled and tapped, using 87 runners and plenum. Just make sure you use the right plenum, I used the wrong plenum initially thinking it was the correct plenum and it took me two months to figure out what was going wrong. Good luck.

 

That was great information, I forgot about the sensor in the front. What was the problem with the plenum? My TPI setup is all original (85) and I know that the ECM setup is the bastard stepchild of the TPI's, but I don't have the typical turn over engine then turn key off , then start up like most FI Chevy engines. The one I have fires right up the first time. I found a 86 Base, so I'll just have to elongate the center holes to fit. This would be less time consuming for me...

 

I used the 88 or 90 plenum over the 87 thinking it was the 87 plenum, causing a massive leak that was a pain to find. I would definitely consider the sensor up front using the newer plenum if you have the correct tap set. Either direction you go, good luck.

 

Did you have a machine shop drill the hole and tap it? What size hole and thread was it? Thanks in advance.

 

No
EGR is on pass side ,comes up from base and exits into plenum through holes behind TB
Cold start on drv side (85 - 88 )
http://www.hotrodlane.cc/Streetstories/choosetpi1.htm
http://www.hotrodlane.cc/Streetstories/choosingtpi2.htm

Mines long gone so can't remember but
If cold start switch is the same size as the heater outlet then is 1/2"NPT
If same size as CTS then 3/8"NPT

 

Check in the 2nd link above.
The '89 and later do not have the 2nd passage cast in the underside of the plenum to match up to the tube that runs down to the intake on the drv side.This means you have a big vac leak using early drv side runner on late plenum unless you seal the tube off

 

So, the fuel from the 9th injector goes up the small runner tube on the drivers side and then travels through the long passage in the upper plenum casting, correct?

 

I do not remember off the top of my head but I can find out, and my buddy works at a machine shop and did if for me, it was actually very easy, and you cant miss the cooling passage so long as you mimic your older manifold, keep in mind you cant go too fast either to keep from melting the aluminum, dont go grandma slow but dont drill crazy fast either.
If you look at Vetteoz post he gives two sizes and i am pretty sure it was the same as the CTS sensor, I actually think they are the same sensor with a different connector, either way I am sure it was the same size as the CTS, give me a couple of hours and I can do a physical check for you.

 

No ;
Once again look at the pics in the 2nd link above.
It shows the plenum difference where the early plenum has a hole behind the TB that connects to the passage cast underneath
That passage is connected to the IAC outlet on the back of the TB.Early intakes have the IAC air coming out a small hole in the bottom of the intake port ; just before the head.
Later plenums ( without the passage ) drop the IAC air behind the TB therefore no passage on plenum or runner