Recently i changed the spark plugs on my 2000 s40 and after about 500 miles the check engine light began to blink and the car would sputter and shake at low speeds an idle. Reading all that i saw on that this model uses best the volvo plugs i went to dealer and bought the volvo plugs and wires...150 buks. Hoping this would fix the problem i changed them and its still doing the same thing. The check engine light had been on for a while because i took off the thermostat while i waited to get one in. But now it blinks. I took it to the auto parts to get the code for the check engine and no codes would come out. Does anyone have any idea what this could be or what i should do?thank you very much. Car has 140000 miles

 

You need to replace the 2 coil packs and 2 ignition wires.

 

I also had a similar problem after I changed my plugs at 100k miles. It turned out to be the coil-on-plug connector on both coils. If you look at the back of the connector where the 2 wires enter, you will see a little rubber o-ring like substance that holds the wires in the connector. After so many miles (and heat) the rubber disintegrates and allows the wires to back out of the connector. The result is that when you push the connector onto the COP, the wires back out just enough to not seat properly on the COP pins. Then after a few miles (vibration) the wires back away far enough to not make a connection and you get a miss.

To test this just get a pair of needle nose pliars and gently push the wires at the back of the connector. If they move forward a couple millimeters then you have found the issue. The fix is to push the wires in so they are fully seated onto the COP pins, then place a dab of high temp RTV on the back of the connector to keep the wires from backing out again.

 

sounds good i will try that i also ordered the ignition coils from the auto parts theyre duralast from advance auto. The volvo ones are 4o buks each more. I hope these will work. Thanks for the advice and any other advice you can give would be greatly appreciated. Thanks

 

I believe Duralast is an Autozone brand (not important just talking out loud). When I bought mine at Autozone, surprise, surprise, a genuine Volvo part popped out of the box.