Thought i'd give TBI a try on the ole 2f

[badass]

Hey, great thread.

I plan on installing a GM TBI this winter so I am following your progress with great interest.
You have received a great deal of input from guys with a lot of first hand experience so I am a little hesitant to butt in.
But for what its worth.
Downey's installation manual and other sources state that the speed sensor must be functioning properly to control idle speed and mixture. The altered speed sensor you are using may not be.

Thanks for the insight Heron Jefferson State Cruisers

Heron i'm glad this thread is of help to you.

Regarding the vss, you are right, the correct vss is a 2 pulse, however downey did not have a 2 pulse vss in stock and had no way of getting one, so Jim sent me a 4 pulse vss with a convertor. Yes it works just fine.

 

[badass]

Need to make sure the pickup in the distributor is as close as you can get it to the star wheel.

Think about it. If it doesn't know your cranking it won't send fuel. Check you wires for good connections.

Troll you are a genius!!!!!!! The pickup was so loose it was moving around, i guess i forgot to tighten the screws. I tightened it up and runs amazing again. If you only knew how many times i have gone and traced every stinking wire But i guess that's a good thing because everything has been triple check.

Also went and bought a new IAC from advance auto, idles on its own now and cold start function works!!!!

Still running rich and throwing code for bad map sensor so i will replace that one and see what happens. I'm getting there!!! Thanks man.

 

[lukebz]

congratulations dude!!!! keep it up

 

[badass]

Alright so replaced map sensor, and still running rich, but maybe i need to drive some more????

Currently running FANTASTIC, other than it running horribly rich. I'm so used to carbs, but i gotta admit this cold start function and no pumping pedal is pretty BADASS! Since my first and only car is my 40 this is pretty neat lol.

I got in it after she had cooled off in cold weather, hit the key and she doesn't even turn more than one time before it comes to life. badass

I got more pics of the stuff i've done and will make a video again soon. Later

 

[OlympiaFJ60]

Please elaborate, i don't know what 15 steps means. Which screw???

The previously mentioned screw on the TB that opens the butterfly a little. The steps are the number of clicks (IAC is a stepper motor) that it is open. Unfortunately you need some sort of scan tool to do this. You could rent/barrow one from your local CSK (AutoXRay is a common brand of consumer scan tool). I don't think it is too much. Then you can see if your ECM is going into closed loop (O2 Sensor giving feedback to ECM to meter fuel) and your IAC position and a few other important parameters.

 

[Texican]

Hey, great thread.


Downey's installation manual and other sources state that the speed sensor must be functioning properly to control idle speed and mixture. The altered speed sensor you are using may not be.

BS I have one and know of 2 others that are functioning GM TBI's with no VSS at all only throws a code at highway speeds.
Butch

 

[badass]

Butch you really think vss is not needed? i have read in the past that people think it is not needed.

However, i have also read that if vss is not used the engine will back fire when in gear and no foot on the gas.

 

[too tall]

I've never hooked up a vss in any of the conversions I've done and they all run fine.

 

[lc69hunter]

What is your vacuum at idle??? The MAP uses that as a baseline and if too low, sends a signal that richens the mixture.

 

[OlympiaFJ60]

BS I have one and know of 2 others that are functioning GM TBI's with no VSS at all only throws a code at highway speeds.
Butch

and that can be turned off in a modified prom.

 

[joeyg1973]

MAP needs max vacuum, make sure you have it plumbed to the correct port.
Knock Sensor on the 2F if it's working should NOT be mounted into the engine block, as the solid lifters will set it off all the time, I would mount it in a bracket and mount the bracket in rubber.
There is one port on the TBI unit that OEM was the PCV it is a "design" vacuum leak, I plugged it on one of my conversions and almost never traced that down.
Are you going into closed loop?
Do you have a way to monitor live data or just a code reader?
Was the truck running absolutely perfect with the carb?

Texican,

Won't isolating the knock sensor on rubber defeat the purpose?

Can you explain how you would make a bracket, isolate it on rubber, and where you would mount it on a the motor?

 

[badass]

Texican,

Won't isolating the knock sensor on rubber defeat the purpose?

Can you explain how you would make a bracket, isolate it on rubber, and where you would mount it on a the motor?

Joey mine is mounted where the original mechanical fuel pump used to be on the passenger side of the motor. The downey kit came with a block off plate that also has a nut welded on it so you can just screw the knock sensor on to it. Now i don't know if this is the best method or not but i just used what came in the kit.

 

[Texican]

Texican,

Won't isolating the knock sensor on rubber defeat the purpose?

Can you explain how you would make a bracket, isolate it on rubber, and where you would mount it on a the motor?

The knock sensor is to compensate for different octanes fuel unless you have milled the head a bunch the 2F will run on anything.
GM mounts them into a water jacket...... transmitting sounds very efficiently. no engine GM has ever used the FI is solid lifters one of the tests you use on GM's is to tap the engine any where and watch the live data, as the knock sensor backs the timing up.....mounting in an empty fuel pump hole is basically the same thing I suggested since it is not in coolant doubtful if it works like it should

 

[joeyg1973]

The knock sensor is to compensate for different octanes fuel unless you have milled the head a bunch the 2F will run on anything.
GM mounts them into a water jacket...... transmitting sounds very efficiently. no engine GM has ever used the FI is solid lifters one of the tests you use on GM's is to tap the engine any where and watch the live data, as the knock sensor backs the timing up.....mounting in an empty fuel pump hole is basically the same thing I suggested since it is not in coolant doubtful if it works like it should

hmm now that I think about it, water is a more efficient transmitter of sound. I bet you that it is tuned to work specifically in the presence of water. Perhaps putting it in one of the many holes in the water neck that you don't need anymore? Maybe even try getting it to work with an adapter on the coolant outlet hookup in the head? I am using one from a Volvo, but my setup is completely custom so I am pretty sure it wouldn't work with yours. Anyway here is the site I got mine from:

http://www.viatrack.ca/

 

[Sputnik40]

BS I have one and know of 2 others that are functioning GM TBI's with no VSS at all only throws a code at highway speeds.
Butch

This is damn nice to know. Have never had my VSS installed - and wondered what improvements I might be missing? Having run at 80 mph and then some on 37" MTRs and a mild 2F with DUI and Downey/Astrovan FI - don't think I'll ever really bother with it....

 

[badass]

drove 30 miles today and it runs pretty good,

still throwing map sensor code and running rich, not so good throttle response, definetely delayed, not good power in lower rpms, but great power in higher rpms.

holds 70 on highway like it never did before, good power on highway. will check vaccum.

 

[badass]

so i checked vaccum and it is 18 on the gauge. hmmmm, i'm thinking that's pretty good.

this is something i've realized, runs really rich at idle (black smoke), and bogs in lower rpms with huge black smoke cloud when first starting out in gear, but once around 2000 rpm it has lots more power, no bogging. Guys at advance auto said if computer is not getting signal from the map sensor then it will run very rich.

 

[OlympiaFJ60]

You really need to get a scan tool to see what the ecm is seeing for the map sensor signal. MAP is measure on a scale from 30 (high vacuum) to 100 (0 vacuum or atmospheric, wide open throttle). Idle is around a MAP reading of 50. Here is a rough comparison of MAP reading to vacuum.

30  35   40  45    50  55   60  65   70  75  80  85   90  95  100
21  19.5 18  16.5 15  13.5 12  10.5  9  7.5  6   4.5  3   1.5   0

 

[badass]

You really need to get a scan tool to see what the ecm is seeing for the map sensor signal. MAP is measure on a scale from 30 (high vacuum) to 100 (0 vacuum or atmospheric, wide open throttle). Idle is around a MAP reading of 50. Here is a rough comparison of MAP reading to vacuum.

30  35   40  45    50  55   60  65   70  75  80  85   90  95  100
21  19.5 18  16.5 15  13.5 12  10.5  9  7.5  6   4.5  3   1.5   0

by scan tool, can i just download that free program and buy one of those cables??? I dont remember what the program is called.

 

[OlympiaFJ60]

That is the best way, that is what I did. It is WinALDL (WinALDL - 160 baud ALDL reader) and it is easy to build the cable from Radio Shack parts (WinALDL version history). There is also a link on that page to places you can buy a cable if you don't want to build one. With this you can read the raw data, ECM data and codes as well as store BLM and O2 sensor data in tables. Makes tuning much easier if you decide to go that route.

If you just want to quickly see some of the data, Schucks, Autozon and others have the AutoXRay EasyScan or similar OBD1 scan tool. Just tell them you need to get the codes/data on a 91 GM truck.

HTH