Fleeting Rattle Under Light Acceleration (Page 1/1)
Kitopher APR 18, 05:36 PM
About a month ago I started hearing a faint rattling sound coming from behind my left ear when in the drivers seat. It only happens when the AC is on, when the car is moving, and when RPMs are between 2.2 - 2.5k. It doesn't happen 100% of the time, but when it does it is always within that rev range. The car is a 1986, with the v6 and 137k miles. I was previously running a Hypertech powerchip and 91 octane, but I thought the sound could be ignition pinging so I am back on the stock chip with 87 octane gas. The sound has stayed the same regardless of the chip or octane level of the gas.
Any suggestion help.
Thanks,

------------------
Kit G

Mike in Sydney APR 18, 06:43 PM

quote
Originally posted by Kitopher:

About a month ago I started hearing a faint rattling sound coming from behind my left ear when in the drivers seat. It only happens when the AC is on, when the car is moving, and when RPMs are between 2.2 - 2.5k. It doesn't happen 100% of the time, but when it does it is always within that rev range. The car is a 1986, with the v6 and 137k miles. I was previously running a Hypertech powerchip and 91 octane, but I thought the sound could be ignition pinging so I am back on the stock chip with 87 octane gas. The sound has stayed the same regardless of the chip or octane level of the gas.




Did you check the timing?
Patrick APR 18, 07:42 PM

...and when you check the timing, make sure to have the ALDL jumper in place.
Kitopher APR 18, 08:08 PM
I have not checked the timing with a light yet. I learned the hard way a few months ago that the markings on my harmonic balancer are no longer acurate(I'm assuming it shifted over time). So I've only ever had the car timed by a shop and I'd have to remark 0* and 10*BTDC myself. At this point it seems like the next logical step, I just didn't do it initialy since I figured the hypertech chip was causing an over-advance, but then taking that out didn't solve the issue. I also forgot to mention in my initial post that the sound only happens under gentle acceleration. If I give the car any kind of pedal it doesn't happen, but during relaxed daily driving situations it usually does.
Patrick APR 18, 08:46 PM

quote
Originally posted by Kitopher:

I learned the hard way a few months ago that the markings on my harmonic balancer are no longer accurate (I'm assuming it shifted over time).



Yes, the outer ring of the harmonic balancer slipping is a relatively common occurrence... and only becoming more common as these cars age. You might wish to invest in a replacement balancer.
Raydar APR 19, 11:43 PM
Is your EGR working? One possible side effect of an inop EGR is pinging. It will also likely fail smog for excessive NOx.
Kitopher APR 19, 11:46 PM
I have not checked the egr, but I can say that the car passed smog 4 months ago. That's not to say it couldnt of failed during that time frame but I feel like that's somewhat unlikely.