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I have a 94 GMC 1/2 ton P/U 350 cu. in. engine, TBI When

Customer Question
I have a 94 GMC...
I have a 94 GMC 1/2 ton P/U 350 cu. in. engine, TBI
When truck is cold runs great, once warmed up to 180 degrees, stumbles and hesitates on acceleration, really noticeable between 25 -45 mph. constant miss, lost of power, sluggish.
I've replaced MAP sensor, EGR soleniode, checked and cleaned EGR valve, spark plugs, spark plug wires, distributor, distributor cap, rotor, water temp.sensor, fuel pressure regulator in TB, ICM twice, reset timing to 0 degress TDC, scan for codes.
no computer codes, no check engine light.
What are your thoughts.
Thank You!
Frustrated
Submitted: 2 years ago.Category: GMC
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Answered in 2 minutes by:
10/9/2015
GMC Mechanic: Gary, ASE Certified Technician replied 2 years ago
Gary
Gary, ASE Certified Technician
Category: GMC
Satisfied Customers: 17,277
Experience: GCM master tech over 25 years
Verified

will it do this with the EGR unplugged ?

this has a brand new distributor in it ?

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Customer reply replied 2 years ago
Unplugged ERG same problem
brand new distributor-Auto Zone
GMC Mechanic: Gary, ASE Certified Technician replied 2 years ago

if you remove the O2 sensor out and drive it quick will the problem go away with the O2 sensor out

i know it will be a little loud but this is just for testing purposes

it is odd it runs good cold and then does this warm almost like when it goes into closed loop and runs fuel control live time off the O2 sensor its reading wrong

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Customer reply replied 2 years ago
I have not tried removing O2 sensor.
GMC Mechanic: Gary, ASE Certified Technician replied 2 years ago

can you see if it will stop doing this with the O2 sensor out

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Customer reply replied 2 years ago
I'll remove O2 sensor this weekend and test drive,
how do I contact you with results?
GMC Mechanic: Gary, ASE Certified Technician replied 2 years ago

just reply right back through this post

you can always get me back through this post for FREE with any follow up with this question anytime even after you rate us here at Justanswer as i do not get credit for my work unless we are rated

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GMC Mechanic: Gary, ASE Certified Technician replied 2 years ago

how are you making out ?

dont forget to rate us here at Justanswer !

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Customer reply replied 2 years ago
Gary: I tried replacing the O2 sensor as you recommended same problem, stuttering, missing after truck warms up.
any more thoughts?
GMC Mechanic: Gary, ASE Certified Technician replied 2 years ago

i asked you to remove the O2 sensors and drive it with the O2 sensors out and see if the power came back

i did NOT recommend you replace anything

i recommended you remove the O2 sensors and see if the truck stops doing this

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Customer reply replied 2 years ago
can I just unplug O2 sensor instead? and see if anything changes?
GMC Mechanic: jazzmaster, ASE Certified Tech replied 2 years ago
jazzmaster
jazzmaster, ASE Certified Tech
Category: GMC
Satisfied Customers: 2,951
Experience: I have been in the automotive industry for over 35 yrs
Verified

hi, when you ,pull a spark plug out are they black and fouled looking ?...jazzmaster..

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jazzmaster
jazzmaster
jazzmaster, ASE Certified Tech
Category: GMC
Satisfied Customers: 2,951
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