MeanYellowZ

Hey all, its been a while.

Anyway, having some problems now with a TBI setup. This has been retrofitted into a vehicle that I am messing with. Its a 92 350 truck TBI that has been transplanted. It appears to be done well, and all stock, actually looks factory in the vehicle. However, the drivers side manifold has been modified by the flange and has no O2 sensor. I searched hi and low and found no o2 sensor at all. Is this do-able? the engine doesnt run bad overall, but I do get an SES light about half the time, and while idling after a period of time in gear (e.g. in a drive-thru) the idle will go up and down repeatedly. The SES light mainly comes on after a period of time on the interstate.
Other problem, engine has been pingin lately a lot. Seems, but not sure, to be associated with cheaper gas mostly. I looked at the timing and it looks to be around 10, maybe 12* BTDC. It does retard quite a bit real fast when you move the throttle blade, I dunno if this is a characteristic of TBI, or just FI engine ignitions in general, but it reminds me of a carb engine losing vacuum, therefore retarding the vacuum advance quickly before it starts advancing.

Any ideas, help would be greatly appreciated. This is my first time dealing with TBI, and i know about as much about it as I do about applying makeup. As far as the O2 sensor, should it have one? Any idea as to where I can find the wire that should go to it? On the pinging issue, too much timing? just use good gas? scrap the TBI??

thanks guys

Randy

Vader

MYZ,

What ECM are you using? Almost every FI control requires an oxygen sensor, and all the TPI units I am aware of certainly need one. Without the O2, the ECM will use the base fuel and spark tables, which are usually too rich and retarded. I'd suggest welding in a bung from a header set and installing an oxygen sensor. There should have been a connector for it (at one time at least).

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Later,
Vader
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If you want to beat the World, it might reach up and pull you down...
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MeanYellowZ

as far as I can see its a factory harness. The vehicle originally came with a 4.3 TBI, and I have read that the harness will just plug into the 5.7 TBI. It may be the original harness from the vehicle. I am going to have to dig up the O2 wire from somewhere.

any other ideas

BTW, glad to see your still here helping out the technical world of thirdgen, i was hoping to see some familiar faces.

Randy

MeanYellowZ

TTT

crazeinc

use that fancy-shmancy welder of yours and weld the damn bung in lazyass

V8Astro Captain

iTrader: (1)

In '92 they changed the wiring harnesses for the 4.3. Before '92 they used the 7747 ECM to run anything from the 4.3 to 5.7. In '92 they still used the 7747 ECM on the 5.7 and 7.4's, but they went to a 16144288 on the 4.3's.

You prolly want to chack and makes sure, but when I did my swap I had to switch pins A-11 and D-2.

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'92 Astro, GM crate 350, Holley Pro-Jection Intake, MSD 6AL, 3.42's, 2.5" exhaust, Flowmaster 40 2 chamber, B&M 2nd stage shift kit, 255 60 R15 tires on AR-727's, Polished & Bored TBI, Custom EPROM in progress

MeanYellowZ

I pulled all the codes out of the computer and got these:

13: O2 sensor (reallly?)
32: Bora Sensor (what the hell is that?)
43: Spark Control Module or something. Is this inside the distributor?

MeanYellowZ

not ready to let this one die yet......