89 Sierra hesitation when getting on the pedal


Asked by Sep 03, 2014 at 09:01 PM about the 1989 GMC Sierra C/K 1500

Question type: Maintenance & Repair

This truck has a 5.7 tbi/700r4 with heddman hedders that have NO 02 sensor bung. There
is no 02 sensor in my truck right now. May be missing some important grounds. will do a
powerbrake like a brand new truck, but on the road dies when i get on the pedal. There is
also no cat and a stock muffler on the truck. Any help will be appreciated, Dave..

4 Answers


Unless the ECM has been modded to operate without O2 sensors it won't run correctly, You could also be having a fuel delivery problem, missing O2 sensors on this model should not make it just die out, it might run ragged but not die. If the catalyst was removed cause it melted down, some of the could have went into the muffler causing an exhaust restriction, if it is restricted enough it will cause a dying problem also. HTH

Andrew Olsen

well the o2 sensors control air/fuel ratios. If anything you are now making less power without them... figure out how to put them back on or just slap a carb on the thing. Now back to the issue. IF a minor problem arises rather its a vacuum leak, seal getting old, injectors not what they used to be, or just and aging engine the truck it can normally compensate for it using the readings from the o2 sensors to make it run the best it can. Now without them the truck will simply run at a baseline that cannot change becasue there isn't anything to tell it otherwise. Also this baseline is a "limp mode" so to speak, you will experiance lower mpg's, less power, and poor idle. And come on, I can power brake a 350 that was running on 5 cylinders. That isn't a measure of power, just a visual of money wasted on tires. Fix that poor truck right


its not just power breaking. On dirt it seems to have good power too. it just falls on its face on the road. Idles fine even when put into gear. could this maybe be TPS along with 02 sensors?


the truck wont kick down when im trying to pass someone either seems to bog out instead

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