kamaroirock

my tach is way off, i rev it and it pegs out what do i need to do?

Benm109

I think your guess is as good as anybody else's. A lot of people have this problem (including me), and there is no direct answer, from what I can find. Have you check your grounds, check for vacuum leaks, etc. If it's none of these problems, you have about three options: get a new gauge cluster from a junkyard, Ebay, etc. and hope the new one works, find a shop that fixes gauges (there aren't a lot), or go to an aftermarket tach. It may also be a good idea to see if the computer reads the same RPM as the tach, just to be sure it's just the tach that's off.

Somebody may have figured out the problem with our stock tachs, and if they have, please post it.

funkyreggaestyl

Yeah i'm kinda having the same problem. Does yours appear to be idling high too? Mine seems to just do it when i'm driving, and appears to be idling high. Like the last guy said check to see if the tach matches your computer. Let me know if you find anything out because it seems to be a preety common problem and i'm working on mine too right now. Thanks, Good luck

kamaroirock

my tach is off by alot at any speed it idles at like 3k or so and goes past 7 and stays there when i get on it. but the motor idles and runs normal

Berlinetta

my boss told me awhile back that there was a electrical thingamajig, sorry, at the back of the instrument panel that goes bad and can cause the voltage to the gauges to go screwy. I wasn't sure what he was talking about but maybe someone else can pick out what im trying to say... i feel like an idiot because i cant remember what he called it.

BTW, my tach is always pegged to the right. Occaisonaly it'll dip down to the left but not usually.

v8nate92RS

Mine is the same way, it idles at 1500RPM and by my best guessing, when I drive normal it is at least 2000RPM higher at all times. I got another cluster off Ebay and put that tach into my cluster to no avail...it does the same thing. SO, I bought a nice Autometer 3 and 3/4 inch tach, but have yet to install it. I still wish the stock one would freakin work!

tennessez281983

i talked to alot of people about the same thing.
then i talked to a inmate at the place i work.
he sad get a dimmer light switch ac or a volume switch off a old ac
stereo. and wire it in from the tach hook up on the dist.
get a hand held tach and turn the dial till both read the same.
works fine just have to hid switch some were

Benm109

I did a ton of research some months ago on this board and alot of people said that the problem was a capacitor on the back of the tach (I think this is what Berlinetta was trying to think of). The solution to the problem is just taking the old capacitor off and soldering a new one on. The only problem is that no one seems to know what rating the capacitor should be. Some say it should be the stock rating and some say it should be a different rating. I may sometime soon try this (with a capacitor at the stock rating), just to see what happens. I have an Autometer tach installed so that way I can check to see if the stock tach is right or not. We'll see how it goes.

Berlinetta

EXACTLY!!! thanks that was what i was trying to talk about... serious brain fart guys

Big AL91

Ditto on the Tach problem. Have Shop Manual, yet to find subject manner on the Filter in the Tach circuit. How to test and what function it plays on our faulty Tachs. Comments? Thanks

MurcoRS

I had the same problem with mine, bought anohter tach in the scrapyard, still had the problem, bought a V6 tach and changed the capacitor as discussed in another thread, same problem! My car's tach filter has to be bad but I cannot locate it (should be inline with the white lead coming from the coil). If I knew what the rating was for this piece, and where it was, I could replace it. Any ideas??

Big AL91

MurcoRS; Thanks for the update on our Tach woes. If we all stay with it, addendum, on page 6D5-8 91 Shop Manual reference Engine Wiring LO3 item 3 Tach Filter Connector, 6D5-9 item 5 Tach Filter. The Connector/Filter shown in the coil wiring harness(loom covered) somewhere between the coil and junction for the distributor harness. Trickster has noted that there should also be a connector relative to timing RPMs I believe, in this same harness although these pages do not. My problem stems from the fact when referenced with the diagram section(91) the filter nor its connection not shown. Another very important aspect of these circuits would be the Ground Connections located on both sides rear of block checking for poor connections and/or broken wires. These Ground Terminals are also below valve covers as further info. I will eventually get there but at the present strugle to mod the TBI air cleaner, so many opinions. I can also tell you what tests to perform for the '91 Tach at the instrument cluster connectors if interested. Good Luck & advise.

Berlinetta

so no one knows where or even what the damn tach filter is?

MurcoRS

I found the diagnostic connector about 4" from the coil in an opening in the loom. Still haven't found the @#&% filter, though... At least there is a replacement available when I do find it! Rodney's Fieros

Big AL91

:hail: MurcoRS; Good Job, patience. If we are real good and he's not beachbound, maybe just maybe we can get Trickster:hail: to post that diagram refered, see the '89 circuit.

Trickster

That is because there isn't a tach filter on your car MurcoRS. There is only the diagnostic connector in that circuit. The tach filter that you are thinking about was used on the earlier distributors with the internal coil. I posted that schematic and filter location on this thread.

https://www.thirdgen.org/techbb2/sho...hreadid=231471

Now in this first picture you will notice that I have circled the tach diagnostic connector, it is labeled "C114". The second picture here shows the location of that connector in the engine compartment. Now as an added bonus I am including at no extra charge, shipping and handling is extra though. A picture suitable for framing, of the capacitors located on the tachometer circuit board that has been mentioned earlier. Enjoy!!!!!!!!!! :lala:

Trickster

page 2

Trickster

page 3

Trickster

page 4

MurcoRS

Well, now I am bummed... I've done that modification already with the new capacitor and I still have the needle pegging! Well, now I have an excuse to get an AutoMeter gauge set...

Big AL91

MurcoRS; you are hopefully outa there. Trickster has and will be a Big Help! Your '92 has a LO3 Vin E 305, unless? So, we do not yet have the correct diagram for our gauge cluster. I have requested of Trickster if it is within his control. As information the post dated 9-10-04 at 819P is correct with respect to the '91 manual that covers 88-92 LO3 Vin Es. If the '92 Manual is in your hands, it might show where Trickster has located the filter and can share.

gogo90camaro

I just swaped out my engine to a 350. I had a 305 in it before. when i first started it up and did my engine check out everything was normal including the idle. the tach was reading double. Has the problem been the same as in the engine swap and the tach?

MurcoRS

Mine is an '89 and I double-checked his schematic against a Chiltons manual I got today, it is pretty-much identical between the 89-92 L03, LB9, & L98 as far as the tach wiring. I did the capacitor modification so I much either have a bad tach (2nd one?) or a bad connection/short somewhere...

Trickster

MurcosRS, when your tachometer pegs out when you turn the key, does it go back to "0" when you turn the engine off? If it doesn't. just turn the car off, disconnect the battery and manually move the needle back to zero very slowly and carefully. Once you do that, reconnect the battery and start the car and watch the needle. I had a situation like this where I removed the dash cluster without disconnecting battery first. When I put it back together with the battery still connected, the needle pegged out and that is how I was able to get it back down. It is still off by about 50 rpms but I can live with that. Here are a couple of tests for you.

Trickster

page 2

Trickster

page 3

BTW, The Tach filters were used in camaros up until at least 1986 and no later than 1987.

Big AL91

:hail: Thank You! Understand, Appreciative.

MurcoRS

No sh*t!! Trickster, your unending assistance has earned unending appreciation from myself, and I'm sure so many others on the board!
Thank you!

Berlinetta

so, if those voltages are correct... then the tach is crap and needs to be replaced?

BTW, i hooked up a snap on diagnostic scanner and it showed the proper engine rpm... so the ECM is reading the correct rpms. Does that point to my tach being bad?