08 IS 250 will only start sometimes. New battery, had alternator tested so far so good. Bought the car about a month ago and check engine light and check VSC light stay on. If I do get it started I have to leave it running while on errands or working because it will not start for several hours. Dash lights up and lights interior/exterior come on along with radio and A/C. It also reads Check Complete but the motor doesn't start. I can't work or commit anything, please, any advice or information is welcomed and greatly appreciated! Also, I did the bang on the starter thing

 

Try spray clean your MAF sensor with CRC MAF Sensor cleaner. Spray and leave half an hour to dry to be safe. Report back. Disconnect from harness of course.

 

I will give this a try and post back results. Thank you thank you!

A. Kitchens

 

How many miles on this?
And can you confirm the engines sounds like its cranking over at its normal pace but fails to start or does it not crank/turn over at all? If the later, does the green light come on when the brake is depressed?
Your first step should be to get the OBDII codes read by any automotive parts store and post them here.
What we have seen on the 250's is the low pressure fuel pump in the fuel tank get gunned up, is unable to supply the required pressure and volume of fuel to the cold start injector/high pressure fuel pump and the engine cranks but won't start.
A quick test for this is Engine Starting fluid or ether. You spray it into the intake track and attempt starting. If it starts, its a fuel problem.
Get some starting fluid. Get the codes read. Tell us some history and everything else you know.