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4.3 liter vortec, need help with strange issue.

7K views 8 replies 8 participants last post by  1Gary 
#1 ·
Hey guys. Truck is a 1994 Chevy S10 SS 4.3 vortec. Engine has developed a strange condition where it will surge every now and then, even while cruising at highway speed with foot off the throttle. It happened while my friend was driving it and she almost rammed into the car ahead of her as the truck just took off on its own, even while she was standing on the brake pedal, as if the throttle and pedal are being depressed at the same time! Did some preliminary checks and Ive found nothing obvious...... No check engine light, no misfire (I think) etc. Without a check engine light on this is very hard to diagnose, Im thinking a sensor is on its way out and signaling for fuel when its not needed? Possibly an O2 sensor sensing a false lean condition and signaling for more fuel? Anyone had similar pblems with these engines?

Thanks,
Keith
 
#5 ·
There is not much room between the accelerator and the brake pedal on S10 vehicles. If the brake pedal gets too low and if you foot is not positioned correctly on the brake when it is applied, you can accidentally depress the accelerator and the brake at the same time. That has happened to me a few times and it is scary. Bleed ABS brakes of any residual air to prevent the pedal from sinking to the level of the accelerator pedal. There were recalls in the 1990s about such incidents and I am sure some were related to the ABS brakes having air in the system.

When I drive my S10, I often wear Simpson high-top racing shoes that have narrow soles. The soles on those racing shoes were designed years ago to be used in front engine dragsters that have a small foot box. You should never wear work boots or wing tips while driving an S10. .
 
#8 ·
This is very unorthodox, but it happened to me; in a 96 S10. I had the cruise control activated and was resting my left foot lightly on the brake pedal; my right foot was on the floor in front of the accelerator. I stepped on the brake for an upcoming exit and the truck surged. My right foot had accidentally lodged the floormat under the accelerator pedal
 
#9 ·
1994/1995 was a transitional yrs for 4.3's.In 1994 it could be either a TBI or with the W engine a CPI that does have spiders that might leak.A fuel pressure check is going to help to better understand one part of this.Also check engine lights doesn't happen often with a clogged Cat.If the problem goes away by removing the 02 before the cat and running it open,then it is likely a clog Cat.
 
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