My car has been vibrating badly after a cold start, and I wanted to take care of some stuff before tackling to find the source. By accident I found that if I turn the car to the on position before starting, there is no vibration. Any suggestions as to what I stumbled upon?

Thanks,

 

When you turn the key ON, the fuel pump runs for about 2 second then quits. You may have stumbled on a fuel-system that doesn't remain pressurized. Or a marginal fuel pump? You could measure your fuel pressure when it's running, also measure pressure after turning off & watch how long it takes to decay.

It's not a bad idea to always pause the key ON before immediately going to START. Still, there's a couple things that might be going on.

- Fuel pump is supposed to have a check-valve to prevent backflow when it's turned off. Big-ish expense so I'd live with this.

- FPR might leak down. New FPR isn't too expensive & not too difficult to replace. Still, I'd measure fuel pressures to know what's going on.

- Injector leaking fuel into intake-manifold. My guess is not, because that would be worse on a warm start. Cold overnight gives plenty of time for puddle of fuel to evaporate.

- Check for yourself to rule out any external fuel leaks. Smell any fuel in the engine compartment? Anytime? If so you might look at replacing the O-rings on your injectors.

 

Thanks for the suggesstions, replacing o-rings and gaskets is on the to do list. I've been having problems with them. If they fix the problem, all the better.