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    Heat box swap

    I think you might have a blend door issue or something wrong in the vacuum controls. The heat in my 90 burb is intense and the air flow on heat (floor) and defrost (top of dash by windshield) is pretty strong.
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    ‘87 454 R20 eye watering exhaust w/ windows down

    .
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    1987 Silverado fuel issue

    you will find the service manuals for the 87 in the Reference Library on this site. they will have test procedures, schematics, etc to help diagnose the selector switch
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    1987 Silverado fuel issue

    this is from the 1990 manual. but I'd suspect your 87 is a similar setup except you might have the complexity of 2 tanks.
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    1987 Silverado fuel issue

    If you apply 12v to the red test lead, you should have 12v at the connector to the pump. The test lead splices in downstream of the relay per the wiring diagram. you can also apply 12v straight to ckt 120 on the harness with the relay disconnected and get 12v at the connector at the pump. you...
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    Engine cranks, but only starts after letting off key? - I'm perplexed

    . It comes in the truck next to the AC box on the outside, and is routed over the large duct on the inside and goes to the ecm behind the glove box in a single bundle.
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    Engine cranks, but only starts after letting off key? - I'm perplexed

    code 42 only sets if there is a wiring issue with the bypass (black/tan) or est (white) wires. could be an open or a short to ground, bad connection at the ICM, or stray voltage from a plug wire touching one of the wires or a bad plug wire or distributor cap letting voltage out and it is causing...
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    Cab leaking

    under the truck behind the fenders are the cowl drain exits. you may need to remove a plastic cover to see them. but you need to pull debris, flush from top, pull debris, and repeat until all the debris is removed. both sides.
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    Regearing Advice... What do I need?

    http://www.grimmjeeper.com/gears.html this is the best calculator I've found. Use your actual measured tire size on the truck, not the spec sheet.
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    Regearing Advice... What do I need?

    http://www.grimmjeeper.com/gears.html this is the best calculator I've found. Use your actual measured tire size on the truck, not the spec sheet.
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    What’s the solution to this?? Idle adjustor

    the cap will come out with a small screw driver or a pick. you shouldn't need to drill it out. better question is - what are you trying to accomplish by adjusting the min idle air screw? the IAC controls the actual idle speed.
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    Gas cap

    My 90 burb TBI has no pressure releasing when I open the gas cap. I'd check out cannister under the hood to make sure it is all connected right and that the vent line from the tank isn't plugged. I think there was a thread on here somewhere about the cannister set up. It's also covered in the...
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    Should my TBI's fuel pressure act like this?

    thanks for that info. I have a L05 engine, so never looked into that for the other engines. All the GM manuals are available in the reference library on this forum. they are a GREAT resource!
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    Should my TBI's fuel pressure act like this?

    my 350tbi (1990 burb) fires in 2sec, maybe 3 sec, on a cold start every time. it fires instantaneously on a hot start every time. fuel pump is newish, and it did the same before and after the pump swap. I don't think the TBI system retains any residual pressure. I always just chalked it up to...
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    Regearing Advice... What do I need?

    I have 3.73 in my v1500 burb (350tbi and 4L60), and don't think the cost is worth it to swap to 4.10 for ~32in tires. Right now i have a cruising RPM of about 2100rpm on the hwy at 75mph and it is certainly plenty serviceable around town also. Although I'd prefer 4.10, its just not that big a...
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    Should my TBI's fuel pressure act like this?

    the pressure regulator controls the pressure between the pump and the regulator that feeds the injectors. it bleeds off any excess pressure into the return line. so you can measure pressure just after the fuel filter at the flex line (where I have my adapter installed) or at the TBI on the...
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    HELP!! 1991 K5 TBI

    code 42 is usually a bad ICM, or stray voltage somehow getting to the white (EST) or tan/black (bypass), or an open or short (sounds like an intermittent issue) in one of those 2 wires or at the ICM connector.
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    Diagnosing A/C not recirculating on mac

    On mine, there is a noticeable difference in the sound of the air when on Max and the door switches from fresh air to recirculate air from inside the cabin. You can definitely hear it change from ac to max ac. If it stopped recirculating, I'd be looking at the vacuum line and the pod that...
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    Now we move into desperation territory (seeking advice)...

    There might be a sticker under the dash by the ECM that has the number in case somebody installed the wrong one? But I'd think you'd have larger drivability issues with the wrong computer. Could also be that they swapped ECM with the new body style and those got a different computer. Might have...
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    A/C only works when driving!?

    It sounds like it is likely electrical, and could be the motor or an alternator issue. But next time try to see if you can get under the hood and check the actual motor to make sure it is not doing anything vs just feeling at the vents
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    Should my TBI's fuel pressure act like this?

    right after key on, yes. it primes for 2-3 sec when key on and then the pump turns off. I don't know if it should drop to 0 during cranking, but that doesn't seem correct. have you looked in the emissions and drivability manual?
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    A/C only works when driving!?

    Air is coming from the right places on those settings
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    A/C only works when driving!?

    Are you missing the vac line that goes to the vacuum reservoir off of that T just downstream of the check valve. I dont recall my setup having a plugged T there. Or does the other line off the other T head that direction to the reservoir? Vac should be good at idle, though.....so I'd expect that...
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    A/C only works when driving!?

    not sure if the OP has specified if the blower stops or just the airflow out of the vent stops. also, try the blower on high because that bypasses the relay.
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    Should my TBI's fuel pressure act like this?

    turning the key to ON will prime the pump for a couple seconds. after the prime, the pressure will bleed off. not sure why the pressure drops to 0 for the first couple seconds of cranking. I've never done that test with mine, but intuitively it seems like the pressure should be there during...

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