Hello Everyone,

I have a 1999 XK8 that I have noticed a vaccum noise for 1-2 seconds when I press the accelerator pedal and then the engine will run. It's like a short pause while making a sucking sound, then the engine kicks in. I recently had the fuel pump replaced by a new mechanic and not sure if this is related. I never noticed the sound before the new fuel pump and its seems to idle a little more rough than before. The car does start up and drive buy I'm not sure what this could be. If anyone has any suggestions, I would greatly appreciate it.
Also, does anyone have any reasonable priced suggestions for tires. The pricing that I.m getting is at $250 and up per tire, guess its an unusual size?

Thanks,

John

 

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Where do you hear this 'vacuum ' sound?

 

Being that the fuel pump was recently replaced I would check the manifold pressure reference for the fuel pressure regulator.

I don't have JTIS in front of me to point you exactly where it is on a 99 but there should be a tube running from the manifold to the regulator to give a pressure reference and it could be that one end or the other is disconnected, which will create a vacuum leak.

 

Thanks Charlie ! I appreciate the feedback

 

Take a look at the intake ducting to the throttle body for leaks. This model is notorious for developing cracks in the accordion folds of the ducting.

 

the 'sucking of air' is normal, but should only be heard at the throttle body.

Upon changing anything related to either air (like cleaning the TB itself or mass air flow sensor or repairing leaks) or fuel/spark (as if a new pump, filter, plugs, coils) I always recommend a hard reboot by disconnecting the neg terminal on the battery and touching it to the positive for 5 sec or so. That will clear all fuel trims in the ECU and the car can adapt much quicker to the changes.

Also, see the FAQ in this subforum and read about adjusting the throttle body cable. Over time, it stretches, and seems like the car has less response, especially initially upon accelerator pedal depression. Its a good read and will give you a little thrill back in driving the car if you make the adjustment.

 

Thanks everyone for the great advise, its been very helpful.

John

 

we do what we can Petey o' the Blue. Don't be shy now that you've started 'talking'.