Question about 1991 GMC Suburban

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Need accurate info on setting the timing of a 1991 gmc 350 tbi electronic controlled engine. Cann't find the connector that need to be disconnected to set the timing. what color are the wire in t

I have searched the wiring harness and only found where looks like three wires are going into one and have been crimped together and taped with electrical tape. I reworked all the sensors and replaced the ECM and Catalytic converter, Truck failed state inspection with high HC(PPM) and NOx(PPM) at low speeds everything else passed.

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Tan with a white stripe located 1 under the passenger carpet near the middle of the hump in the floorboard 2 in the engine harness near the fuse relay center may have to peel the wire loom back to find it timing at (0) btdc with connector unplugged

Posted on Dec 07, 2012


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Posted on Jan 02, 2017

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SOURCE: 7 wire harness going to blower motor resistor

There is an updated resistor/connector package. Very expensive from GM, try your local NAPA or other parts supplier for a replacement

Posted on Jul 09, 2009

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SOURCE: I need to know the wiring color codes for a 1993

Please look at page two. It shows most connect cross reference to Bosch Universal 4 wires O2 kit.

Posted on Mar 06, 2010

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SOURCE: abs code co223

if u taped up the wiring so its weather tight and the abs light reset [went out] then u corrected ur problem and should last

Posted on Jun 01, 2010

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SOURCE: emission test 25/25 hc ppm read 00170 allowed

  • There are a couple things here that could be the issue. One would be your Catalytic Converter. The other would be your 02 sensors. It is possible you are running just a little bit rich. There is a sensor on the exhaust not far off the manifold (this is called the upstream sensor). There is another 02 sensor down the exhaust a bit by the Converter (this is called the downstream sensor.

  • Most of the time you will know when the 02 sensor is bad because your fuel mileage will go way down. Often times a check engine light will come on as well (but not always). A failure 02 sensor will run a vehicle rich and that left over fuel from combustion can cause pollution and a failure of an emissions test. However, if you are not loosing any fuel mileage, and you don't have a check engine light on I would be inclined to think that the converter has passed it's point of functionality and needs to be replaced.

Regards, Tony

Posted on Apr 29, 2011

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SOURCE: I have a 1988 gmc k2500 with 5.7 tbi. The gauges

Some thing in the instrument panel has shorted out or the wire from the fuse to the panel., pulling to many amps. If you could do without the panel for two days you would find out if it's the panel or the wires before. Electrical problems are no fun. I'm into a Ford that I just got running (second day) And there are still problems. (stupid computers). For the wires a good place to start is behind the fuse panel

Posted on Jul 05, 2011

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Here, is what I think you are asking. The TBI intake from a 91 will fit the same size engine from 88 to 95. The Vortec didn't come out till 96 I believe. So if your 91 is the original engine then it is not a Vortec motor. If you want to swap your 5.7 with another 5.7 (5.7 = 350) Then the 88-95 should work, Just double check your sensors and locations as the plugs may be different and or in different locations. I know my 88 GMC and my 94 chevy (both K1500's) were a little different. Hope this helps.

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