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Gary
Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 17006
Experience:  15 years GM master tech
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GM Silverado 4x4: I have a 1999 Chevy Silverado 4.8l. I'm getting

Customer Question

I have a 1999 Chevy Silverado 4.8l. I'm getting the following Codes:
P0420
P1635
P1639
P0332
Trucks seems to run fine except for it is very sluggish, with poor throttle response. It feels almost like there is too much "pressure" when im accelerating, if that makes any sense. Plugs, oil, and all superficial fluids were changed recently, did not affect it either way.There is also a slight tick coming from the engine that wasnt there before, similar to an exhaust manifold leak or lifter tick, but not sure which.
Submitted: 2 years ago.
Category: Chevy
Expert:  Gary replied 2 years ago.
these issues may all be related or noti think we should try to see if the cat converter is plugged or restricted which will cause the 420 and the 336 codesif you remove the O2 sensors out of the exhaust manifolds before the cat converter and take it for a ride will all the power come back ?it will be a little loud with the O2 sensors out of the exhaust but this is just for a quick road test and will not hurt anything
Customer: replied 2 years ago.

I can do that, but it will be a bit later. I've never removed O2 sensors, what am I looking for and what do I need to remove them?

Expert:  Gary replied 2 years ago.
a 7/8 wrenchremove # ***** and # ***** is fineyou can always get me back through this post any time with any follow up for free with this question even after you rate us here at Justanswer !
Customer: replied 2 years ago.

Do I need to remove the modular end of the sensor or do I need to remove the probe itself from the exhaust?

Expert:  Gary replied 2 years ago.
just unplug them and remove both and un screw them out of the exhaust