Where would I find such an object. While I just started posting here I have been watching this forum for a few years. I finally got posting privlidges yesterday.

So anyway. Someone mentioned one of my problems may be a tach filter. I have seen it spoken of before. No manual I have found for the fiero speaks of such an thing. Where do I find it and how much is one?

Here is an article about the tach filter. http://www.fieros.de/en/articles/tachfilt.html

Rodney Dickman sells replacement ones too. http://www.rodneydickman.com/retail_new.html

You can buy one from Rodney Dickman or the Fiero Store. They range from $18 to $40.

Or if you want to go the DIY route, you can make one with a few bucks worth of parts. Here's the electrical schematic:

quote Originally posted by Blacktree: You can buy one from Rodney Dickman or the Fiero Store. They range from $18 to $40. Or if you want to go the DIY route, you can make one with a few bucks worth of parts. Here's the electrical schematic:

Even though just about everyone will tell you that the above tachfilter is for all Fieros, it's not. It is in fact the tachfilter used in the L4 only. This is the tachfilter for the V6:

Or just put a jumper wire in its place and be done with it.

Did that two years ago and never had a problem.

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quote Originally posted by Cliff Pennock: Even though just about everyone will tell you that the above tachfilter is for all Fieros, it's not. It is in fact the tachfilter used in the L4 only.

That's interesting. Do you think there would be any problems if one were to use the 4cyl tach filter on the V6? I ask because I noticed that after I replaced my 4cyl with a V6 (also modded the 4cyl tach and built a tach filter using the schematic I posted), the tach only goes up to about 4500 RPM. If I rev the engine higher, the tach falls to zero. After the RPM drops below 4500, the tach comes back to life.

BTW, what do "8n2" and "3k3" mean?

[This message has been edited by Blacktree (edited 10-23-2007).]

quote Originally posted by Blacktree: That's interesting. Do you think there would be any problems if one were to use the 4cyl tach filter on the V6? I ask because I noticed that after I replaced my 4cyl with a V6 (also modded the 4cyl tach and built a tach filter using the schematic I posted), the tach only goes up to about 4500 RPM. If I rev the engine higher, the tach falls to zero. After the RPM drops below 4500, the tach comes back to life.

A tachfilter is essentially a low-pass filter meaning if you are using the wrong one, it could exhibit the problems you are experiencing.

quote BTW, what do "8n2" and "3k3" mean?

8n2 = 8.2 nF, 3k3 = 3.3 kOhm

Thanks, Cliff.

edit to add: I also think my engine has a "torque filter". Because if I rev it above 4500 RPM, the torque falls to zero. But I think that's a subject for another thread.

[This message has been edited by Blacktree (edited 10-23-2007).]

I can say that if the tach filter goes bad, it will release the magic blue smoke from the coil. I tried to catch the magic blue smoke and shove it back in, but failed. I assume that the sticky brown goo dripping out of the coil held the smoke in.

I ended up getting a new coil and building a tach filter.

Blacktree, that torque filter you speak of, it came factory on all V6 Fieros, it's called the Intake manfiolds :P

But on the tach filter subject, I bought Rodney Dickmans non oem looking one, and it was very easy to install, and came with instructions. If you decide to buy one instead of make one, i'd highly recommend Rodney.

Just for fun. I see that you guys like to post images of your cars. Could someone show me an image of where this thing is located and what a correctly installed one may look like.

By the coil, little metal round cylinder

quote Originally posted by Hudini: By the coil, little metal round cylinder

thank you. Thats what the one on the 2.5 looks like as well?

Oh, don't know. Anyone with an '84-'86 Duke know? (I have an '87 with DIS 2.5L in a non-Fiero)

quote Originally posted by deceler8: Or just put a jumper wire in its place and be done with it.

what does the filter do

Anyone have a picture of where the tach filter is located on the 88 duke?

Thiis is the location on the 86 duke that I have. It's the grey item by the end of my thumb. The white squarish connector is for the tach filter



This my daughters 85. It's the grey item in the center of the pic


On one 84 that I had it was hidden by the large wire bundle down there. edit: Both these engines have been out of their respective cars, so the location could be anywhere in that general vacinity. It's mount should be on one of the bell housing bollts

I have no idea where it is on an 88

[This message has been edited by 2farnorth (edited 10-19-2008).]

quote Originally posted by Xerces_Blackthorne: Anyone have a picture of where the tach filter is located on the 88 duke?

'88 is DIS so it probably don't have one. Lots of good changes were made in '88. Anyone know?

quote Originally posted by serealport: what does the filter do

It’s an RF noise filter. Without it your AM radio would be very noisy, especially between stations while tuning. The filter also reduces the amplitude of the pulses going to the tach which may make the gage more stable.

The filter isn't needed on the DIS engines cause the ignition module tach output signal is clean.

what is the voltage for the capacitors

quote Originally posted by deceler8: Or just put a jumper wire in its place and be done with it. Did that two years ago and never had a problem.

Can you really just put in a wire in place of the filter? Cause if you can, It would be awesome take the taped up mess of crap I have been using off.

[This message has been edited by Riddick85 (edited 10-21-2008).]