Hi Ralph,

Your problem sounds like the crankshaft sensor could be position incorrectly (shaken lose due to Engine vibration). Or the sensor is going bad.

This sensor is required for the ignition system to work correctly. The crankshaft sensor is use to tell the computer where the engine pistons are located with respect to engine stroke (Power, Exhaust, Intake, Compression) so the engine computer can calculate the spark plug timing. The only time the computer diagnostic system can detect a bad crankshaft sensor is when the sensor misses the timing mark located somewhere on the crankshaft (sometimes the manufacture will locate the crankshaft sensor on the camshaft, I am not yet familiar with Volvo engine sensor locations). If the computer diagnostic system can not detect a fault/bad sensor then it is up the technician to diagnose the problem the old fashion way by gut feel and do some experiments (i.e. replace the sensor and see what happens and so on…).

A bad temperature sensor could cause the timing to go out. The sensor could be telling the engine computer that the engine is cold when the engine is hot. This would make the computer run the engine with a rich gas mixture and could cause a backfire. This would also account for some extra power. An old carbon monoxide commando trick it to install a switch/resistor across the engine temperature sensor telling the computer that the engine is cold when the engine is actually HOT, hence you now have a rich mixture and WHAM an extra 50hp! Burn them tires! Check your gas mileage. If the gas mileage has gone way down then this could be your problem. Also a stuck fuel injector could emulate this problem. A stuck fuel injector is easy to detect.

One only other explanation I can think of at this time is a possible bad wire/connector. I doubt this is a problem. Volvo did a good job on the wiring. However, it should be looked at.

I agree with Eric G. Your Dealer should fix this with no excuses! If the Dealer can not fix the problem then contact Volvo After Market Sales Representative. He/She will get it fixed for you.

And one last note. Driving a car around with this kind of problem can damage the Catalytic Converter! A Catalytic Converter is an expensive item to replace so get this fix as soon as possible. If you need more help let me know some more details and I will see what I can dig up for you.

Good luck!

Steven---