[pontifex4]

I did my best to search for this, but didn't get a lot of traction with 'my car sounds like an airplane when I turn the key.' Anyway, while the starter is running and for the first couple of revolutions under its own power, my new 968 makes a "putt-putt" exhaust-type noise very similar to a tractor or propeller airplane motor starting up. The noise is easiest to hear from the driver's side of the car with the hood closed. It does not seem to be the starter, since it persists briefly after the engine is running.



It's the same hot or cold: about five "putt" noises in a row, after which it idles and runs very smoothly and quietly with no lifter noise. Revving the engine doesn't seem to cause a similar noise.

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[pontifex4]

[quote name='pontifex4' timestamp='1343073407' post='129827']

I did my best to search for this, but didn't get a lot of traction with 'my car sounds like an airplane when I turn the key.' Anyway, while the starter is running and for the first couple of revolutions under its own power, my new 968 makes a "putt-putt" exhaust-type noise very similar to a tractor or propeller airplane motor starting up. The noise is easiest to hear from the driver's side of the car with the hood closed. It does not seem to be the starter, since it persists briefly after the engine is running.



It's the same hot or cold: about five "putt" noises in a row, after which it idles and runs very smoothly and quietly with no lifter noise. Revving the engine doesn't seem to cause a similar noise.

[/quote]



I hope I haven't put this in the wrong forum. It has been suggested that if my timing were off, I could be hearing something like this until the engine is fully running (after which, presumably, I can't hear it over the sound of the engine).



Thoughts?

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[94SilverCab]

Not ignoring you, completely mystified....



???



Jay

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[tamathumper]

No clue. My first thought was you're losing fuel pressure and the engine is just turning over and getting a few drops of fuel and "chuffing" until fuel pressure builds back up, but that's a complete WAG.

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[flash]

do a blink test if you can and look for a hall sender code. being a canadian car, you may not be able to, and will need to connect a durametric or hammer

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[RS Barn]

Look at resonator at both ends to see if there is any telltale deposits from moisture. A cracked exhaust can react funny until exhaust gas temp comes up.

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[pontifex4]

"do a blink test if you can and look for a hall sender code. being a canadian car, you may not be able to, and will need to connect a durametric or hammer"



This is actually a Florida car, but my Canadian 944s all had the diagnostic port. I'll see if I can find my light and try it.



[quote name='RS Barn' timestamp='1343159171' post='129914']

Look at resonator at both ends to see if there is any telltale deposits from moisture. A cracked exhaust can react funny until exhaust gas temp comes up.

[/quote]



This is what seems the most likely to me, since it really sounds as though I can hear one cylinder's exhaust valves opening and closing for that brief period. However, it happens hot or cold.



In any case, I'll finally be able to put it on the lift this weekend and have a proper look around.

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[flash]

cool - i presumed that you had already put the car in the air and looked for leaks. obviously check that first.

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[pontifex4]

[quote name='flash' timestamp='1343161875' post='129918']

cool - i presumed that you had already put the car in the air and looked for leaks. obviously check that first.

[/quote]



Yeah, it's really killing me that I haven't had time to dig into it yet. The first thing I do may be to change the FPR, since I think it's original (130K miles) and the fuel pump is really whining. I'll update this thread with my startup noise findings, in any case.

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