1987 blazer 5 k

[Jetstarrfire65]

Hey guys, looking for info on an 87 k5, we have changed just about everything, all sensors, throttle body, distributor, ecu, and it still runs rich. Blacken all the plugs. Loads up and runs like ****.

 

[fast 99]

Open EGR, low manifold vacuum, high AC voltage, bad ground.

TBI relies primarily on MAP for fuel trim especially until O2 warms up. Have seen defective new MAP sensors. Try to find a used GM part.

 

[RecklessWOT]

I agree. Just because the sensors are new doesn't mean they're good. A lot of the cheap aftermarket reproduction parts for this simple old tech actually is bad right out of the box more often than I'd like to see unfortunately.

When you say it runs like sh!t, do you mean there are driveability issues, or does it just idle rough and run rich? What specific symptoms are you having? Are you positive the injectors are spraying a nice pattern? Does the thing sit around a lot, how old is the fuel? etc. Anything you can think of is helpful, please give us more info than we need, then we can pick through it and maybe spot something that was overlooked...

 

[RecklessWOT]

Also, being in CO, does the thing have the high altitude emissions package? I forget the RPO code but it will say it right on the sticker. If your trck was always in Colorado then there's a good chance it has it, it was only available at some dealerships in Colorado back in the day. My '87 suburban is originally a CO truck (bought it in Loveland and drove it back to New England), it is high alt emissions. Without it, maybe your truck just isn't loving the lack of oxygen? The fact that they came out with a special option makes me think there was actually a need for it and not just some gimmick, it was a no-cost offering. What part of Colorado are you in? Do you run 85 or 87 octane?

Edit: here's a picture of the RPO codes from the window sticker. 350 TBI, high altitude emissions package, Colorado truck. If you don't have a lot of info on the rig, at the very least look to see if it has the NA6 code on the sticker in the glovebox

You must be registered for see images attach

 

[Jetstarrfire65]

Ok thanks will check it out. It does run and drive just acts l8ke a vehicle that has a ch9ke stuck or idle mix is off plugs are black with unturned gas like 9ne with a carb running to rich. It has a rebuilt tbi. But not sure if it is work8ng properly. Is there a way to change it for altitude? Tune chip or chang8ng anything in emissions ?