QuestionQUESTION: When I hold the brake on my 93 toyota pick up 4 cyclender 4x4 I get a surging idle. When I let my foot off brake it goes back to a normal idle. Also every once in a while my engine light comes on and the code is a 25 oxygen cencer what cencer might that be?
ANSWER: The oxygen sensor is located in the exhaust pipe in front of the catalityc converter but that may not be the problem, the problem that should be addressed first is the one concerning the brake pedal and the engine surging because this is probably causing the O2 sensor code, there is a good chance that the power brake booster has an internal leak, there is constant engine vacuum applied to the brake booster, when pushing the brake pedal the booster uses this vacuum to assist the braking, if there is a leak it's the same as a vacuum leak on the intake side which will cause the engine to do what you say, the solution is to replace the brak vacuum booster.
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QUESTION: I replaced the vacuum booster and it did not fix the problem. What should I do now?
ANSWER: Has the large vacuum hose from the manifold to the booster been checked for a leak, there is a large vacuum leak on the intake side.
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QUESTION: I spraid the whole motor with carb cleaner and WD40 with no change in Idle. I changed the inline valve for the vacuum booster line and I did an inspection of the line. What might i do next?
AnswerWhat you told me in your original question that the surge is only there when the brake pedal is depressed is typically a leak inside the brake booster, if it was a leak before the brake booster then the brake pedal would not cause this and the surging would be there all the time, what happens if you disconnect the vacuum line to the booster and plug it up, does the problem then go away?
