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proautotech
proautotech, Auto Mechanic
Category: Car
Satisfied Customers: 1243
Experience:  College Training. Current Lead Tech
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i have a 95 tahoe thats falling on its face when taking off

Customer Question

i have a 95 tahoe thats falling on its face when taking off .i recently changed the fuel filter plugs pcv i un pluged the map sencer today and it runs fine .when i got a new one and plugged it in it went back to doing same thing any one no whats happening
Submitted: 2 years ago.
Category: Car
Expert:  proautotech replied 2 years ago.
Thanks for trusting us with your problem. I have trained in the automotive field and currently work as a lead technician. I will be helping you today

Can you monitor the fuel pressure while driving?

You can put the fuel pressure gauge in the windshield so you can watch what is happening.
Customer: replied 2 years ago.

I dont have a gauge. Do you think it's the fuel pump? It runs fine when I unplug the map sensor. Will I damage anything if I drive it w/ the map sensor unplugged? Is there a way for me to bypass it?

Expert:  proautotech replied 2 years ago.
Where did you get the new map sensor from?
Customer: replied 2 years ago.

I got it from a friend of mine who works at Advanced Auto Parts. He had it in his basement w/ a bunch of other parts. The part was not in a package. He told it was good. Told me it was new


 

Expert:  proautotech replied 2 years ago.
Interesting.

I do not know if I trust it.

We can test.

With it connected probe the green wire should be 4.8 volts with the key on. If voltage is low check the grey wire has 5 volts. If they are ok replace it.

Still have the same problem we need to check the fuel pressure. As MAP sensor controls the pressure so when you remove it this can allow it to run ok.

proautotech, Auto Mechanic
Category: Car
Satisfied Customers: 1243
Experience: College Training. Current Lead Tech
proautotech and 4 other Car Specialists are ready to help you
Customer: replied 2 years ago.

Im not sure I understand. Replace what? If the reading is okay, replace the map sensor? Or fuel pump?

Expert:  proautotech replied 2 years ago.
If the readings are good than replace the map sensor as it is not a wiring problem.
Customer: replied 2 years ago.

If the readings are good, and I replace the map sensor and it is still bogging. Should I replace the fuel pump?


 

Customer: replied 2 years ago.
,

If the readings are good, and I replace the map sensor and it is still bogging. Should I replace the fuel pump?


 

Expert:  proautotech replied 2 years ago.
I would not replace the fuel pump until you verify the condition of the pressure.
Is this gas or diesel?
Customer: replied 2 years ago.
Gas
Expert:  proautotech replied 2 years ago.
So it should read 9-13 psi.

If not than we have a fuel pump issue. When you press the pedal if it drops below 13 than you know the pump is struggling.

But checking those voltages may lead us to a bad wire bad MAP or even a bad PCM. So we should start there!
Customer: replied 2 years ago.
Its fin when I jump on it it only does it when I come to a stop or take off what is the pcm
Expert:  proautotech replied 2 years ago.
PCM is the powertrain control module.

Let me know how it goes.

We will find the issue.

I would not hesitate removing and cleaning the throttle body and checking for vacuum leaks.
Customer: replied 2 years ago.
,
Customer: replied 2 years ago.
Ok ya the fuel mileage is terrible to I don't no if that is common with bad map sencer,
Expert:  proautotech replied 2 years ago.
Yes it can do that for sure.

So check the map and get back to me.
Customer: replied 2 years ago.
Ok have a good nite
Expert:  proautotech replied 2 years ago.
You do the same.

I should be available anytime tomorrow.

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