engine problem? 2003 automatic coupe.

[Nick Palafox]

Hey all. Gots a question, and yeah, I intend to take the car in to the dealership since it has only 9000 miles on it and it's still under warranty. My last visit to the dealership was sorta unsatisfactory in the sense that the techs couldn't find anything wrong with the car. There were several warranty issues I wanted to have addressed but as I mentioned they didn't find anything wrong. One of those issues was that occasionally the engine "bogged," but not often and not badly...except once. Having mentioned this to you good folks on this board it was advised that updated software be uploaded. Anyway's, a problem that I've only recently started having is that once starting the engine I can floor it and every time, but for only an instant, right before the engine roars I can hear what possibly might be a vacuum rush sound. Kinda like air escaping or somthing very similar to that sound. What concerns me even more is that yesterday morning listening to it do it again, I punched it (while it was in park) and I swear there were two very small backfires. In anticipation of what I might hear at the dealer, do any of you's have any advice or comments as to what's happening and how I might approach the dealers tech with some idea as to what I'm talking about? As always your help is GREATLY appreciated.

 

[c4c5specialist]

HI there,
Did you ever have a check engine light?????
If not, my theory is as follows.
The rush you hear is the momentary push of air pressure past the throttle body blade.
The engine does not have a IAC control valve to control this noise, so it is a byproduct of the design.
No problem there.
As for the backfire when it park, this is normal, as the computer will not allow full throttle punch in park, and will taper back fuel, and then if you continue, will bounce off the rev limiter earlier than the redline indicated on your tach.
I feel both are normal, given your year and what youare experiencing.
The BOG that you may or may not feel could be your torque management kicking in during aggressive maneuvers. This is to assist the driveline to absorb massive torque shock to the driveline. This may be why you feel it sometimes, and not others.
Allthebest, c4c5

 

[Nick Palafox]

Thanks for responding!!


No, the check engine light doesn't come on, but what you say makes sense. In fact, the day I posed this question I asked my next door neighbor (races motorcycles and is a great mechanic) who was outside and he thought the same thing about the air pressure on the throttle blade. He (nor I, obviously) didn't know about the computer preventing full throttle punch in park. Does this "backfire" sound something like glas paks (I believe that's the name I'm looking for)?

 

[c4c5specialist]

Yes, it could sound like paks.
Allthebest, c4c5

 

[schmaltzr]

I know what you mean about the 'bogging', I was making a quick left turn in front of traffic that was comming at me at 50 mph so I thought I would 'get on it'. Unfortunately the engine throttled back to a less than impressive excelleration. I'd never felt that in a car before, but read about it on the internet. You might try to take the active handling off to see if it does it again, but be careful, without the active handling you can get into trouble real fast and I wouldn't recommend it in the rain or where you might hit something if you loose your control momentarily.