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1986 Blazer TBI problem?

12-22-2004, 11:36 AM
Hey guys! I have an interesting problem here that is abou to drive me nuts. I have an 86 Blazer that I just did a 2.8 to 3.4 swap on. I reused my original TBI intake and system from the 2.8 and swapped the injectors for a set from a 4.3 as well as the other required parts for this swap (balanced flexplate, oilpan and pickup etc..) I also removed, cleaned and reinstalled my fuel tank while the 2.8 was out of the vehicle. My problem is this. The truck runs so excessively rich, at idle and at speed, that your eyes water and burn just from standing near it. It will idle semi OK, a little high on idle speed but not rough, but it eventually loads up and dies. If you drive it it will stall and die upon any acceleration just like when the accelerator pump is shot on a carburetor. I replaced the O2 sensor, the temp sensor and the EGR engine temp vacuum switch. The Check Engine Light will occassionally come on but then go out after the requesite number of cycles without a fault and it stores a code 45 (rich reading at the O2 sensor). I have tested, statically, the MAP sensor, TPS sensor and the Engine Temp sensor and they all are within the acceptable voltage and resistance ranges outlined in the repair manual. Also, my check engine light will occasionally not work. What I mean by this is when you initially start the vehicle and it lights up everything for a bulb check, the check engine light will not come on. If you ground the diagnostic terminal it will not flash anything, not even a code 12. I pulled the cluster and the light is good and the connection is ok. It will intermittently start working again or go out. My questions are: Is there any way to tell if the check engine light issue is a wiring issue or a bad ECM? Do I need to invest in a OBD I code scanner (not a reader) and check the actual operating signals from the sensors and the dwell to the injectors or will that get me any additional capabilities over what I am already using? I have heard from several sources that voltage through the check engine light is critical for proper operation of these early TBI systems. Sorry for the length and thanks in advance for any advice/help.


12-22-2004, 11:54 AM
Do you still have the 2.8 injectors? Put them back in and see how it runs. Should be some lean when cold but the ECM should put it closer when in closed loop after a couple miles. The computer has only so much range for this though. Full throttle operation will not be very good maybe as the injectors go into full open and will be undersized somewhat. Worth a try.

12-22-2004, 09:59 PM
Do you think that maybe the injectors from the 4.3 are too big for the 3.4? Maybe you should consider purchasing the proper injectors for the 3.4.

12-24-2004, 02:57 PM
yea stop being cheap get new ones

12-24-2004, 02:58 PM
i have a 1986 and the engine IS small :-( looks small too

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