Truck is 2wd 5.3 v8 non flex fuel When driving anywhere from 60mph to 80mph rpms rise when I lightly tap or touch the brake pedal. I also get intermittent abs and brake warning lights when hitting bumps

2 Answers 2


I think you have two different issues here.

The first one sounds like you have a vacuum leak in your brake servo/booster. When you press the brake, the booster uses vacuum provided by the air intake of the engine to assist with braking. If there is a leak in the booster, unmetered air will be allowed into the engine air intake which will make the engine act as though you have pressed the throttle slightly causing an rise in revs.

The second fault is likely a faulty ABS electrical cable running from the vehicle body to the sensor on one of the wheel hubs. The wire is likely snapped internally causing an intermittent connection when it flexes when going over bumps.

  • Just replaced wheel hubs and sensors. I have checked for vacuum leaks. would it be possible it could be a booster damaged internally? Also my brake pedal is firm but not hard or spongy and abs still works. my wheels don't lock up
    – Joe.
    Commented Apr 4, 2023 at 22:46
  • Bad grounds? Possibility?
    – Joe.
    Commented Apr 4, 2023 at 22:54

When cruising at a steady 60-80 mph on level ground you'll be in overdrive and your torque converter should be locked up. If you hit the brakes even momentarily, either overdrive or the torque converter or both will disengage. This is the normal and intended behavior, and either will cause your RPM to rise while maintaining a constant road speed.

When overdrive disengages, RPM will rise at the same instant that you tap the brakes. When the torque converter lockup disengages, RPM will rise as soon as you get back on the gas pedal. In both cases, RPM should fall to its previous reading when the algorithm decides that the excitement is over and it's time for a steady cruise again.

To diagnose the ABS problem, you need to read codes. Come back with codes and someone will help you.

  • No codes present when scanned. lights are random could take 3- 4 days or twice a day. even with the lights on no code.
    – Joe.
    Commented Apr 4, 2023 at 22:44
  • Faulty ground/s maybe ?
    – Joe.
    Commented Apr 4, 2023 at 22:52
  • @Joe. Check your brake fluid level. If the vehicle has a brake fluid level sensor and the fluid is low, bumps would cause sloshing and a low fluid warning.
    – MTA
    Commented Apr 5, 2023 at 1:21

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