Tbi problem

[93yukon]

So I'm having problems with my tbi as stated above. It's been giving me some problems starting. It's intermittent. It's not fuel related as it's running 8psi. I tried starting it today and when I turned it to key on engine off the tachometer jumped all over the place and while trying to start it was jumping all over the place and essentially flooded it out. I tried to crank it about 4 more times same thing. Let it sit for about 10 mins cranked it again and fired up. What and where should I start to find out what's going on it seems like the pick up coil or something is on its way out but I'm not sure any help is greatly appreciated!!! Tia!

 

[PlayingWithTBI]

8 psi is way low - should be at least 11. The tach jumping could be a bad connection at the distributor or "HEI shielding - an open ground ckt 453 may result in EMI, will result in induced electrical "noise". The ECM looks at this noise as reference pulses. The additional pulses result in a higher than actual engine speed signal. The ECM then delivers too much fuel, causing the system to go rich. The engine tachometer will, also, show higher than actual engine speed, which can help in diagnosing this problem."

 

[PlayingWithTBI]

Here's some help

https://www.gmt400.com/threads/88-95-service-manuals.43575/

 

[93yukon]

8 psi is way low - should be at least 11. The tach jumping could be a bad connection at the distributor or "HEI shielding - an open ground ckt 453 may result in EMI, will result in induced electrical "noise". The ECM looks at this noise as reference pulses. The additional pulses result in a higher than actual engine speed signal. The ECM then delivers too much fuel, causing the system to go rich. The engine tachometer will, also, show higher than actual engine speed, which can help in diagnosing this problem."

Not to sound like a dummy but what is emi? What can I do to fix the hei shielding and open ground circuit 453? I will go out and clean both connections on the distributor today and put some dielectric grease on them. I have a whole other dizzy that was working when pulled should I swap over the icm from that?

 

[93yukon]

I'll also recheck fuel pressure at the throttle body while I'm in there.

 

[PlayingWithTBI]

EMI = Electro Magnetic Induction, it may be creating pulses to the ECM due to a bad connection making and breaking.

 

[93yukon]

Fuel is good it's running 12 +- at the tbi after a fuel filter change I did this morning. So should I do as I asked take and clean connections on the dizzy and dielectric grease them to see if that is the cause first and foremost? Or could it be my plug wires arcing somewhere maybe?

 

[93yukon]

EMI = Electro Magnetic Induction, it may be creating pulses to the ECM due to a bad connection making and breaking.

Which connections besides the distributor connections should I look into? Any others?

 

[PlayingWithTBI]

Yeah, I would check your connections at the dizzy and grounds at the T-stat, back of passenger side head, and battery. There are others under the dash near the steering column too. The grounds could be your issue with your tach.

 

[93yukon]

Yeah, I would check your connections at the dizzy and grounds at the T-stat, back of passenger side head, and battery. There are others under the dash near the steering column too. The grounds could be your issue with your tach.

Awesome thanks for the help I'll look into it all tomorrow hopefully. It's about to storm really hard here and I don't want to end up caught out in it lol
I really appreciate the help I'm just lost when it comes to electrical Gremlins. I can turn plenty of bolts and nuts but when it comes to electrical I'm dumbfounded