1993 Pontiac Sunbird LE v6 mileage: 59,000. After filling the tank recently the engine speed became erratic: it would race while driving (tach at 1800 forcing me to keep my foot on the brake in a 25 mph zone); when braking for a turn it would vary wildly between a couple hundred and 1500 rpm; if breaking quickly rpm would fall to under 400, would sputter and stall unless I would two-foot. It continued to do this intermittently, sometimes stalling while cornering. I took it to the dealer for its 60,000 mile scheduled maintenance; they found no problem except a possibly partially clogged fuel injector. I used some OTC fuel injector cleaning stuff to no avail. Took it to a very good independent mechanic. He spent three days checking sensors, motors, valves, computer, draining and replacing the fuel. Everything independently checked out A-OK. He's mystified. What do I do now?
You will have to scan your computer for fault codes. We recommend a scanner that you can buy that work just like your mechanics. They read the data stream and give you all the trouble codes that are malfunctioning on your car. You can look up the trouble codes. Once you have replaced all the sensors that have failed you can use the same scanner to clear the check engine light. Check for vacuum leaks.
January, 13, 2014 AT 1:08 PM
Sounds like a vacuum leak. Start with the break booster in particular. Codes wont tell you that. When the diaphram goes bad your car will do just that. Dont wait til it causes an accident like my friend did.