90 r1500 subruban acting up.... Help

[1987 GMC Jimmy]

Well, I’d test the pickup coil before trying a spare because the distributor’s gotta come out. I actually have to replace mine this week. With no MAP, it’ll just richen up to a limp home mode. It’ll smell, but it won’t run like it is now. Not even close.

 

[4WDKC]

You can rent a pressure gauge at your local parts store, your deposit is refunded when you return it. Fuel pressure is my primary thought, secondary is that cap and rotor need to be replaced. Disconnect the tps and start it see how it runs, this will put it in limp home mode.

 

[Vbb199]

You can rent a pressure gauge at your local parts store, your deposit is refunded when you return it. Fuel pressure is my primary thought, secondary is that cap and rotor need to be replaced. Disconnect the tps and start it see how it runs, this will put it in limp home mode.

Even with the voltages being correct on the TPS, you think I should still try it?

I didn't think of renting one

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[4WDKC]

Even with the voltages being correct on the TPS, you think I should still try it?

I didn't think of renting one

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technically its not right but its current situation isnt causing the issue, I had mine down .47v after dremeling out the bolt holes. Disconnecting tells the emc there is an issue with a sensor and causes the ecm to operate on preset values and not pay attention to the sensors, if it runs good this way sensor is your issue you just have to determine which one. If not then you know its fuel, ignition or mechanical issue.

 

[Vbb199]

technically its not right but its current situation isnt causing the issue, I had mine down .47v after dremeling out the bolt holes. Disconnecting tells the emc there is an issue with a sensor and causes the ecm to operate on preset values and not pay attention to the sensors, if it runs good this way sensor is your issue you just have to determine which one. If not then you know its fuel, ignition or mechanical issue.

Unplug map and tps and fire it up? Or just one at a time and try

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[4WDKC]

Just the TPS

 

[Vbb199]

Just the TPS

I'll try it after work... Will post up results

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[Vbb199]

Just the TPS

Won't stay running without TPS plugged in....

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[Vbb199]

Won't stay running without TPS plugged in....

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HOLY **** BUT IT WILL RUN WITHOUT THE MAP SENSOR

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[Vbb199]

Won't stay running without TPS plugged in....

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Edit: it won't run with the tps unplugged * my bad

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[Vbb199]

Better news is, I have a functional spare from a tbi 350 I stripped

You must be registered for see images attach

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[Vbb199]

OK, now.... I swapped out that map sensor, now it won't stay running, I have a 3rd MAP sensor that I can try, but I have to wonder if this is really the issue?




Edit again: same thing, unplug MAP, truck runs with check engine light

Edit again again: plugged map back in, unplugged temp sensor, Truck runs, but wild idle.


Last edit: MAP off of RUNNING 89 burb didn't change anything.

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[Vbb199]

Some additional information to add.... I got my gauge fixed... So I was able to measure vacuum on the motor.... 20 inches of mercury anywhere I checked... So she's strong in that aspect.. Next up is fuel pressure.

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[4WDKC]

You need something to show you live data. If you are computer savy you can make a cable for cheap.

https://www.gmsquarebody.com/threads/connecting-with-a-laptop-with-tuner-pro-rt-and-diy-cable.13194/

 

[Vbb199]

You need something to show you live data. If you are computer savy you can make a cable for cheap.

https://www.gmsquarebody.com/threads/connecting-with-a-laptop-with-tuner-pro-rt-and-diy-cable.13194/

Before i take it that far, I'm gonna check the fuel pressure sometime this week, and see where she's at....
She'll run flooding the motor with fuel, but won't run at all with MAP/TPS regulated a/f mixtures......

I would have to deduce the fuel pressure is low if that makes sense.

If I check pressure, and it's not within that 9-13 lbs, last step IS hooking up and seeing what's going on from a computer, because I have nothing left after that

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