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Rhythmic "clock ticking" noise relative to speed, in gears & neutral, only engine on?
[1980 928 5-speed US]
3 Days ago, the car developed a rhythmic ticking/slapping noise after a trip around San Deigo. It sounds like an office wall clock. It is not too loud but very noticeable when the windows are up. The speed is around 1 tick per second at about 35mph, which accelerates relative to an increase in mph (comparable to wheel speed), No ticks while stationary idling. Here are more details I found while troubleshooting:
- Ticking NOT relative to rpm
- Ticking is strictly rhythmic, not random and equally spaced between ticks.
- Only present if engine is on???? (While rolling in neutral in a parking lot, I turned off the ignition and the noise is gone even if the car is still rolling at the same speed)
- I jacked up the car and tried spinning the front passenger wheel. No ticking or rattle. Wheel is firm with no play.
- Steering has no effect on it
- Noise *seems to be coming from near the front passenger side (not sure, heard within cabin)
History:
Most recent work done:
- September: Muffler fell off, replaced with Borla Cat-back
- July: Shop replaced Timing belt, Laso water pump
- February: Shop reinstalled entire emission control system
Existing problems:
- Gearbox is in terrible condition
- Clutch fan spins slow, pusher fan doesn't work
- Engine mount weak
- Rear calipers usable but bad
Thank you for reading and I appreciate any and all help!
-Ed from Orange County, CA
PS: This is my first post after lurking on the forums during 3 years of ownership of my "cheap" 5-speed 928. I had never worked on any car in my 18 years of existence (family was aginst it) before owning the 928. Your knowledge and help allow me to do what I have always wanted to do, and be proud of my car and my work on it. I love this community and enjoy every second with my 928, in and out of the garage. The ownership experience is way better than my previous newer cars. Parts are easy to find (comparing to my 90's Japanese car) Documentations are everywhere and the community is great and crazy smart. I look forward to speaking to you guys!
This is it! The noise was coming from it. Gone when I unplugged it. Thank you! Any idea if it is okay if it just unplugged like this? Edit: apparently it only affects the dashboard light. nvm!
Last edited by ohno; 10-09-2023 at 07:59 PM.
Reason: apparently it only affects the dashboard light. nvm!
This is it! The noise was coming from it. Gone when I unplugged it. Thank you! Any idea if it is okay if it just unplugged like this? Edit: apparently it only affects the dashboard light. nvm!
Early cars with O2 sensors had a mechanical counter tied to the speedometer pulse, which would trigger a warning about replacing the O2 sensor. I think they were 60k miles?
Mine had the same clock ticking sound.
Early cars with O2 sensors had a mechanical counter tied to the speedometer pulse, which would trigger a warning about replacing the O2 sensor. I think they were 60k miles?
Mine had the same clock ticking sound.
Andrew
Do you know if an '83 US spec 5 spd would have a mechanical counter? I have a similar ticking noise I haven't had time to diagnose yet.
Probably, since it is an L-jet injection, correct? Easy to check for the counter, it's under the cover between the passenger seat and the door sill. Rectangular box is the original stereo amplifier, the odd shaped piece is the counter.
Probably, since it is an L-jet injection, correct? Easy to check for the counter, it's under the cover between the passenger seat and the door sill. Rectangular box is the original stereo amplifier, the odd shaped piece is the counter.
Andrew
Thanks, yes it's an L-Jet injection. I have that cover off at the moment and will check it out. Is there a solution other than unplugging it?
Edit: I found a photo I took previously of that area. So that appears to be the 'catalytic converter counter switch' in the front. Is that a capacitor for the radio/amp behind it? Thanks again.
Do you know if an '83 US spec 5 spd would have a mechanical counter? I have a similar ticking noise I haven't had time to diagnose yet.
Mine does. It is under a carpeted cover between the passenger seat and door. Remove the thumb screws and there it is. Took me a while to figure out where that clicking was coming from too.
10-09-2023, 06:08 PM
Rhythmic "clock ticking" noise relative to speed, in gears & neutral, only engine on?
