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Q: Trouble starting and acceleration bogs down

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My truck is having a lot of trouble starting and it bogs down when I accelerate from a stopped position. When it idles, it is a bit higher than normal. Another problem is the shifting which is very hard to shift between gears. I have replaced all of the sensors and also the fuel filter. Would you give me advice on what I should do next to fix my truck's starting problem?

Hello there, thank you for asking about your 1986 GMC S15. You don’t say whether you have an automatic or manual transmission, so I’m not sure how to help you with your shifting concern. As far as the engine performance problem goes, the first place I would look would be the idle air control valve (IAC). The IAC allows a small amount of air to bypass the throttle to control idle characteristics. If the valve is faulty, the engine may not get enough air and stall. Other potential causes for your concern include, but are not limited to, vacuum leaks or a faulty sensor. There are too many potential causes to list, so I suggest you have your vehicle inspected by a professional. A certified technician from YourMechanic can come to your home or office to diagnose your shifting problem and replace the idle air control valve if necessary.

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