98 chev 1500 w/167,000 miles. Exp excessive surging when engaging rev. Must have brake pressed hard when doing so. Also wants to keep going and or gradual increase in speed while traveling forward. Applying brake harder and much too often. When coming to full stop, the tachometer will stay @ 1500to2000-RPMs for a full 3 to 5 seconds before idling down to 900/1000-RPMs. Idler motor has been replaced.
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My 1st guess or 1st instinct would be to say it's a computer software issue, becasue I can't think of anything mechanical that could cause this type of issue. I suggest instead of asking here, you contact your car dealer or manufacturer.
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Hold on, more infromation is needed.
What model 98 Chev do you have.
When did the problem start. Were brake pad JUST installed???
Is the peddle hard to push. Is the vacuum hose broken at the
booster or at the manifold.
i think there's an air leak in your brake booster. Just try to disconnect the vacuum hose going to your brake booster and plugged it use a vise grip to press it. The idle shld go down if there's an air leak
I would unplug the parking brake switch and see if the light goes out. The erratic idle indicates a possible vacuum leak, check carefully around the throttle body mounting. Since it sat for a long time the throttle body gasket may be leaking. Check the intake manifold for tightness too. You probably replaced the PCV valve already. Leaking head gasket, may want to do a compression test. I did some checking and unfortunately your mileage may not be that far off, I got a wide range of fuel mileage ratings from 11mpg to 14mpg. That being said, a malfunctioning emissions system or restricted exhaust could cause excessive fuel consumption. Any chance a rat climbed in your tail pipe and built a nest? Ha Ha Ha. You haven't mentioned any check engine lights being on, still there could be an emissions system problem.
Two issues...
The brake booster has a ruptured diaphragm. Replace the booster.
It is located under the hood between the brake master cylinder and the firewall.
Your master cylinder may be leaking fluid internally past the plunger.
Have it examined when you change the booster.
the idle air control solenoid or a vacuum leak on backside of intake the hose that goes to pcv valve.they are both common problems on this car.check for vacuum leak firstthanks for your question....
Here is the most common cause of surges and stalls, it is the idle speed control air-bypass valve and throttle valve, they get full of gunk over the miles and cause idle issues (stalls) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.
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