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968 Low Revs 'chirp'


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My 1993 968 Coupe, bought used at 51,000 miles and now at about 90,000 miles, has an issue where any acceleration causes a loud chirping, or perhaps pinging (for lack of a better word) sound below about 1300 rpm, even in first gear off the line. Above these start-off revs, there is no detectable problem and performance seems normal. Belts and rollers were replaced at 60,000 mi, well before the problem began. I have recently replaced all filters, plugs, cap and rotor - and checked my timing and balance belts (perfect condition and tension) - no change whatsoever. I use only 93 Octane fuel - from a variety of sources - and have run my last two tanks with Techroline at the prescribed doses. Mobil 1 0W-40, with regular changes.

The only conditions which improve this somewhat are cold engine / very cold weather starts and the exact opposite, a hard-run up-to-temp engine. Is this ringing a bell for any of you experienced 968 wrenches out there? On my very short list are: Variocam, MAF.

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Loren,

I'll check but nothing changed when I removed the old plugs (about 15,000 miles use) and installed a new set. I use copper antiseize and check gap - a real stickler - so it's unlikely. However, I did not know this bit of wisdom and I will check for it. Thanks.

Peter

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you say any acceleration, but then say below 1300rpm - so, i assume this is only first gear, as i don't know how you could get into another gear below that rpm - does it do it above that rpm?

is the sound rhythmic?

does it do it sitting in the garage?

if yes in the garage, does it do it with your foot on the clutch?

Edited by flash968
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Yes, primarily first gear. But the same thing happens if I am rolling in second at 1000 and gently accelerate. Problem disappears above that rev level. It is not rhythmic, more of a screech that immediately stops as revs rise above idle. I can make it do it parked by blipping the throttle abruptly from idle, or by holding the brake and slightly briefly engaging the clutch enough to load the engine in the idle range. So, off clutch or on clutch makes no difference.

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