Help In Id'ing A Tbi Harness

Delray · December 8, 2009

I have this 92 1500 2WD shortbed that came from the factory with a 4.3 5 speed. Some butcher put a 454 TBI with a TH400. Now before I start to get this running the way it should I need to Know if there is a BB harness, ECM and TBI on it or is is this the 4.3 electronics trying to run the 454. I ordered helms manuals for the 92, they are not here yet.

What do I look for to ID/year the harness, TBI and the ECM?

How do I correct the tach being off 6-1000 RPM?

I'm already looking for a 4L80, but I need to know what year.

Does anyone have a 90-95 454 tbi truck that can take some pics for me?

Steve

Mike G · December 8, 2009

Check with GrampaDirt, he is running the 454 in his 95 Burb. As far as the wiring, you should be able to run all but the ECM from the 4.3. You may need to dig a little into the trans set up though. My guess is the TH400 is there because any electronics required to properly run the 4L80 are not present.

--Mike

grampadirt · December 9, 2009

Hi Steve,I'd be glad to help.I see you need pics first of all.Unfortunately the next day I can take some is Thursday(day off).I'll bet that front suspension is groaning trying to carry the weight of the 454.My 95 does have a TBI on it and because it's a 454 the fuel pressure needs to be 26-32psi,V6s & small blocks 9-13psi(per Haynes).The book says the 454 fuel pump is heavy duty.So it would seem if you're running the small block pump the 454 would be starving for fuel.My 95,I think,is a little different than the 454s up to 93 or 94.Look and see if your EGR valve is on the front of the intake and is vacuum operated or if it's on the side of the TBI mount and is electronic(4 wires going to it).If you have the vacuum operated EGR valve I'm thinking it will make it easier to get the proper wiring for it & a 4L80E.Keep in mind I'm not a wizard at this ECM computer controlled stuff but I wanna help.Let me know

Mike G · December 9, 2009

Let me toss this out there... I would presume the TBI unit is specific to the 454, they were beefier than the small block units. With that, the fuel pressure should be reguilated at the TBI unit, I do not think the in-tank pumps differed, but that is something to look at. There is a site I like to look over which has a lot of TBI info, it is:

http://www.cfm-tech.com/

--Mike

grampadirt · December 9, 2009

That's a cool site Mike,I'll have to check it out more tonite after work

Mike G · December 9, 2009

Here are a couple other good sources in case you have extra shopping time..

http://www.xtremefi.com/

http://www.tbichips.com/

I enjoy the reading, very informational. --Mike

grampadirt · December 10, 2009

Here are a couple other good sources in case you have extra shopping time..

http://www.xtremefi.com/

http://www.tbichips.com/

I enjoy the reading, very informational. --Mike

I checked out those sites,lotta info there.I've checked tibchips before and feel the guy sounds honest and sincere.Prolly go there when I someday order an ALDL cable fo my laptop and send the info he needs.CFM-Tech seemed like they were more for small blocks.

Didn't GM stop using TH400s in their trucks in the late '80s?.

Steve,could you post a pic of your engine? I'll be taking some pics of my 454 in a little while

A little info on trannies...Wikipedia,GM transmissions,it mught help identifing what you have

Heavy Cruiser · December 15, 2009

1990 was the first year of OD trans.

I used to run a Hypertech Stage III chip and gained 10% mileage.

Would love to install a 454SS camshaft in at time of overhaul, but I don't think this will ever happen as it has 75K miles now.

Delray · January 2, 2010

Hi Steve,I'd be glad to help.I see you need pics first of all.Unfortunately the next day I can take some is Thursday(day off).I'll bet that front suspension is groaning trying to carry the weight of the 454.My 95 does have a TBI on it and because it's a 454 the fuel pressure needs to be 26-32psi,V6s & small blocks 9-13psi(per Haynes).The book says the 454 fuel pump is heavy duty.So it would seem if you're running the small block pump the 454 would be starving for fuel.My 95,I think,is a little different than the 454s up to 93 or 94.Look and see if your EGR valve is on the front of the intake and is vacuum operated or if it's on the side of the TBI mount and is electronic(4 wires going to it).If you have the vacuum operated EGR valve I'm thinking it will make it easier to get the proper wiring for it & a 4L80E.Keep in mind I'm not a wizard at this ECM computer controlled stuff but I wanna help.Let me know

The EGR is Vac, sits right between the TB and the water outlet. 90 was the last year for the TH400 I found out from another site. I'll get some pics. Thanks Guys.

Steve