Author Topic: 85 K10 Boggs Up Hill/Under load  (Read 808 times)

Offline Patman

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #15 on: May 28, 2019, 11:00:30 PM »
Ive had a difficult time really understanding what is going with my truck. I think I have the issue understood but not quite sure what the problem is.  I still have yet to try the multimeter and positive terminal on the distributor test. Only because the only person that can help me is also my ride if I get stranded. Still below is the full description of the issue im having.

From cold, I can start the truck after a pumping the gas 3 or 4 times, itíll start but I have to keep my foot on the gas a little to keep it running. About 5min of that and itíll keep running on its own. Seems to idle a bit low to me. I can let it sit there practically all day long, just like that and itíll run, no problem. When I drive it, after sometimes 5 min or even as much as 20 min of driving (the hotter it is, the quicker it happens) itíll feel like a switch was thrown and Iíll lose a near 25% power and the engine runs just a little rougher than before. Then with my foot on the gas and without moving my foot, withn just a second or less, the engine will rev and the truck will take off, I have to let up off the gas just a bit to keep from going too fast. Then it starts to lose power again and will run rough but keep a speed of 45-55mph. However, if I have to drive up an incline, the truck will eventually slow down to 35mph or so and will stay there no matter how much I feather the gas. Sometimes itíll run so rough that it kills the engine and wont restart for another 5 min or sometimes even 20 or 30 min. After the truck is done resting, itíll start right up and may drive just fine for the next 30 min or longer even a couple hours once.

While its acting like this, if I have to come to a stop, when I accelerate again the transmission shifts late and hard and I can not find overdrive until Iím at 70mph or more. Down shifts are also loud and hard, kind of klunks into the gear its down shifting into.

But when its running right, it shifts super smooth both up and down and right on time.

The way it happens so instantly, it makes me think itís a vacuum issue. Problem is, Iím not sure what each check valve on my vacuum system is or what components do what, or even how to test it. Remember, its a California truck so all of that smog stuff has to stay.

I could take one or two pieces at a time to NAPA and just replace everything that way. I cant do it all at once or Iíll forget what goes where...

Driving me nuts. Ive replaced so much, once I get this sorted sheís gonna be a runner...
85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33ís
All stock except for the motor, used to be a 305.

Offline JohnnyPopper

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #16 on: May 29, 2019, 05:23:56 PM »
Have you checked your EGR valve? Sounds like it could be getting a vacuum signal when it's not called for.

Pull off the vac line and seal it with a golf tee and drive it.

Offline Patman

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #17 on: May 29, 2019, 07:49:01 PM »
Will do.
85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33ís
All stock except for the motor, used to be a 305.

Offline Patman

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #18 on: May 30, 2019, 11:35:35 AM »
Still happening...

85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33ís
All stock except for the motor, used to be a 305.

Offline JohnnyPopper

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #19 on: May 30, 2019, 12:08:33 PM »
It could be stuck by corrosion of carbon buildup. I would pull it and see if it's gunked up.

Think about it, if it is opening at all during driving, it is allowing exhaust gas to recirculate into the intake manifold, diluting the air/gas mixture randomly.

Do you live where smog is required? if not, plate it off.

Offline Irish_Alley

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #20 on: May 30, 2019, 02:20:28 PM »
you should be able to depress the diaphragm by hand and the engine should about stall or stall at idle
If you canít tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Patman

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #21 on: May 30, 2019, 06:55:14 PM »
Ok, Iíll give it a shot.
85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33ís
All stock except for the motor, used to be a 305.

Offline Patman

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #22 on: May 30, 2019, 07:11:55 PM »
Irish, when I put a hose on the EGR and apply vacuum, the RPMs drop and and it begins to stall.

Does that mean its good?

« Last Edit: May 30, 2019, 07:35:22 PM by Patman »
85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33ís
All stock except for the motor, used to be a 305.

Offline Irish_Alley

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #23 on: May 30, 2019, 09:36:20 PM »
sounds right. i dont even have a clue about how the smog stuff works, but i would almost start where BD suggested
Rig up a voltmeter between a verified stable ground and the B+ terminal on the distributor so that you can monitor the distributor supply voltage while you drive.  Go for a road test and have an assistant drive.  Watch the voltmeter while the symptoms are occurring.  Does the voltage become erratic or is it constant at 14+ volts?
If you canít tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Patman

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #24 on: May 31, 2019, 07:18:17 PM »
Agreed. Iíll try to check it this week...
85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33ís
All stock except for the motor, used to be a 305.