thunderstick

supposedly there is a filter in the tach circuit, and i was wondering if it's integrated in to the tach itself, or is it a stand-alone item somewhere? or actually in the ignition module?

KAM

Benm109

I can't say for sure if it's like this on all the 3rd gens, but on mine, the tach filter is located on the white wire coming out of the gray connector on the ignition coil. It is about 3" or 4" down past the connector on the coil. The tach filter just looks like a single gray one-wire connector. It's usually kinda hard to see, since it's back in between the motor and the firewall.

Big AL91

B-109, you have actually seen this filter, please? Thanks

Benm109

I'm not sure if I quite understand your question, but yes, I have seen it. I can get a picture of it tomorrow morning and post it.

Big AL91

Thanks again. So informed that the filter is not where you say it is, in the wiring loom a short distance from the Distributor connector. '91 LO3TBI305 in my case. The picture would be great and appreciated.

thunderstick

yea, i'd like to see it, too, so i know what i'm looking for. all i know of is the diagnostic connector...

phess11

Here is where it is on 83s

phess11

another

Benm109

Turns out I am wrong.

What I thought was the tach filter is really just that diagnostic connector, C114. After looking through my service manual, I realized my mistake. What's odd to me is that the service manual mentions a tach filter, but doesn't give any clue as to where it is, integrated or not.

But, according to this thread, there are no tach filters after 87 (go down to Trickster's posts):
https://www.thirdgen.org/techbb2/sho...ight=autometer

And in this thread, it says the tach filter is integrated into the electronics of the tach:
https://www.thirdgen.org/techbb2/sho...ht=tach+filter

I'm truly sorry about this mix-up.

Big AL91

B-109, thanks for the update. If a human doesn't do anything, no mistakes are made, appreciate the try. Just to let you know I have the manual for the '91 and the Tach filter is shown where you originally stated although in the loom harness. However The Trickster pointed out it did not exist there but on the printed circuit board of the inst. cluster. As info, my pointer stays at about 7000 with the switch off and pegs about 1500 RPMs. So, even if the filter is faulty and corrected, there is the problem of recalibration, some just carefully remove and reapply the pointer with statements I understand is about as good as it will get. Unless, you were lucky enough to get a tach put together by someone Tues, Weds or Thurs whom cared.

Vader

That's about the same location for the filter as on the C3 Corvettes, except they share a bracket with the EGR solenoid.

Apeiron

Not every car has a tach filter.

Big AL91

Thanks all; the point of my remarks is that the LO3 engine wiring section Camaro Service Manual 6D5-9 shows a Tach Filter in full view. The fact that its not there is disappointing to those of us who rely on the Service Manual especially DIYs.

Trickster

If you go through the pages there for all the engines in section 6d5 for the 91 camaros, you will find the tach filter listed. However if you go to the schematics section for each of those engines, you will find it listed as the tachometer diagnostic connector

Big AL91

Trickster, oh wise one , I yield and thanks.

thunderstick

roger all that... question answered. thanks.

OUTATIME GTA

iTrader: (2)

trying to find out why i have a bouncy idle at WOT, i have a msd setup including the 6AL.

sooo since i have an '89 i don't have a tach filter, but i could possibly have to replace this capicitor behind the guage huh?
i didn't read why. ..they just go bad sporadically?

PhLaXuS

I haven't read up on this particular circuit, but I can tell you that when electrolytic caps fail, they usually leak their electrolyte. Not always -- but usually. if that component went bad, it's usually for a reason and the replacement will probably die from the same reason if you do not find the cause. It could have simply been old age or a defentive component to start with, but this is unlikely. If it were me, I'd replace the defective part & if it went bad again, then I'd find out why. Remember, polarized electrolytic caps do not like AC current or any reverse-biasing (More-or-less: current flowing against the expected direction of current flow.).

vernw

iTrader: (2)

If your tach is acting weird with an MSD ignition, try connecting the tach port on the ignition box to the tach wire from the coil )disconnect it from the coil and drive it from the ignition box). That's what I had to do on my Digital 6+ anyway....

OUTATIME GTA

iTrader: (2)

what about the use of their "tach adapter"?

vernw

iTrader: (2)

Didn't need it!