I just completed a TBI to TPI swap on an 87 blazer and I'm having problems getting it running well.

History: The donar car was a 87 5.7 trans am. I have 22# injectors(cleaned and flow tested with in 2% of each other). New EGR, MAF, and painless wiring. I ported the Plemun by grinding down the two ledges just inside the throttle body bores. The throttle body has a air foil and I by-passed the heater lines around the throttle body. The truck engine was mildy modified when rebuilt with flat top pistons, RV cam, balanced rotating assm., and mild porting to the heads. The truck has a Endelbrock TES headers,y-pipe and a flowmaster cat back exhaust.

The problem: Once evething was hooked up I started the truck and set the timing. The idle is hunting around alot and the enigne stumbles like its missing. An error code of 45 was set (O2 sensor rich). The stumble is not limited to idle conditions only, I tried reving the engine up and holding 2000 rpm and it still would not run smoothly. I checked fuel pressure 42 psi at idle with vacuum pulled and plugged. Idle vacuum 21-22 psi, when the engine is not stumbling. The number on the prom from the donar car ABWT 8674 (I barrowed a friends autoXray and it said 8201??). From the FAQ page this prom should be from an 87 5.7 engine code 8 with auto tranny, Fed emission and 3.27 gears. Any help will be much appreciated.

Thanks
Mike

 

I'd first address the 02 error code problem by installing a fresh 02 sensor or insuring that it's properly connected.

Jake



[This message has been edited by JakeJr (edited January 24, 2001).]

 

The o2 sensor was not getting hot enough at idle and giving a false rich signal to the computer. This is cause by having headers. Once I took it out for a drive it ran great. The o2 sensor would still cold off and the motor would start running crappie again if I sat at a long light. Has anyone converted to a heated o2 sensor??

 

I have converted to the heated O2. They have three wires, two one color and one the other(black and white). The two that are the same color are for the heating element the other is the signal to the ECM. Hook the single wire up to the old o2 wire. Ground one of the wires that are the same color (I did mine under the dash) and run the other to switched power... only on when the ignition is on(I found a handy spot in the fuse box)
I ran an inline fuse in case of shorts.

------------------
1988 T/A,
9" Ford, 3.50 gears, Auburn posi, 700r4 -w- 2100 converter
350 .060 over with forged 1 pc rms crank, and forged TRW pistons, 9.5:1 cr
Factory GM heads Pocket ported, 2.02/1.60 valves, back cut
Lunati roller 219/227, .479/.480, 112 LSA
Holley 700cfm 4bbl on TBI truck 7747 computer and chip by Howell-EFI
Edelbrock Performer EGR intake, Edelbrock TES and 3" cat