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jazzmaster, ASE Certified Tech
Category: GMC
Satisfied Customers: 2951
Experience:  I have been in the automotive industry for over 35 yrs
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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 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!
Submitted: 1 year ago.
Category: GMC
Expert:  Gary replied 1 year ago.

will it do this with the EGR unplugged ?

this has a brand new distributor in it ?

Customer: replied 1 year ago.
Unplugged ERG same problem
brand new distributor-Auto Zone
Expert:  Gary replied 1 year 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

Customer: replied 1 year ago.
I have not tried removing O2 sensor.
Expert:  Gary replied 1 year ago.

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

Customer: replied 1 year ago.
I'll remove O2 sensor this weekend and test drive,
how do I contact you with results?
Expert:  Gary replied 1 year 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

Expert:  Gary replied 1 year ago.

how are you making out ?

dont forget to rate us here at Justanswer !

Customer: replied 1 year ago.
Gary: I tried replacing the O2 sensor as you recommended same problem, stuttering, missing after truck warms up.
any more thoughts?
Expert:  Gary replied 1 year 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

Customer: replied 1 year ago.
can I just unplug O2 sensor instead? and see if anything changes?
Expert:  jazzmaster replied 1 year ago.

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