Tach reads high by 1.5k - Honda Prelude Forum

92preludesi_TX · 09-25-2005, 02:34 PM

I am looking for some help.

I just finished installing EL gauges in my 92 Si. I had a problem with the tach with my first set. The tach needle assembly was broken and wouldn't return to zero. I had to replace it with one from a jdm cluster. Anyway, yesturday everything was working fine. I checked today and the tach is messed up again in a different way. The tach will return to zero when the car is shut down and the key is out. But if I put the key in and turn to 1, the tach jumps to 1.5k.

At first I thought it would have to do with the wiring. I checked the tach wire and ground and they seem to be fine.

Does anyone have any idea how I could fix this?

92preludesi_TX · 09-25-2005, 07:38 PM

Update:

I just got home from some errands...

when I started the car the tach was fine. It was where it shoudl be.
While I was driving though, I noticed that it raised past where it should have been. Then, when I was going to start my car to head home, before I cranked the engine, the tach showed 1k rpm.

Any ideas? Please help...

GaRn · 09-25-2005, 09:34 PM

Hmm not sure, when I cut mine on its a bit off as well.. It says 1,100 at idle, when my datalogger shows 840-860..

btw, nice color

LudemanDan · 09-26-2005, 01:30 AM

Subscribed.

GaRn · 09-26-2005, 06:54 AM

Quote:

Originally Posted by LudemanDan

Subscribed.

I guess the sender uses voltage to control the tach needle?

Wonder if there is a way to calibrate it?

Si_g · 09-26-2005, 02:44 PM

I had a similar problem...my tach started acting the same way...but that was when I had my stock Si gauges. My problem was my distributor was bad...it was a little rusted, but from what I saw...it was the ECM (eletrical control modul...It is a little module located inside the distributor) that was damaged.

My symptoms were that the tach would start jumpin either when the car is off and i put the key in the ignition and turn to 1 or 2 ( i would watch it go up and down a few time, then have a hard time starting) or from 3k to 45k while im driving, or the car would just plain shut off at a light while idling, or even while driving, or would have a hard time starting up....

I replaced the distributor with a new part from Honda for 280 bones...that was just for the distributor...Honda wanted a total of 400 or 450 for the complete kit, which included the ECM and the cap...From what they told me at the time, they didnt sell the ECM separatly, so either I were to get the distributor alone, which I did for 280, or the whole kit in the 450s or 480s i dont remember...I ended up finding the ECM at Pep Boys for 75 bucks. (No other part store stores such as napa, discount, autozone and a few others even carried this part)

I have not had any of the symptoms described above everything I changed my distributor with a new one from Honda, and a ECM for Pep Boys.

I hope this helps...good luck.

92preludesi_TX · 09-26-2005, 04:08 PM

That problem sounds about right. The problem I am having though is that my engine isn't really idleing high, the tach is just reading high. I can tell that it isn't idleing at 2000 rpm and that when I am driving, even though at one point the tach read over 7500 rpm, I wasn't even close to redline.

I did a small test yesturday: The wire that sends the tachometer signal is located in the yellow M Harness that plugs into the guages. I pulled the M harness out of the guages to see what would happen. When I did, the tach stayed at 1.5! This makes me believe that it is either the needle that is something with the guages and has nothing to do with wiring.

I am not sure what I am going to do. I drove this morning and the tach was high again. Then this afternoon it read like it should. It is very frustrating.

Si_g · 09-26-2005, 04:45 PM

well the fact that you had to replace needles is probly the reason why it is sittin at 2k when its not really idleing that high. Those things are usually tricky. When i got my first set of EL gauges, my tach did not work right, at idle, it was at 0, but the car was idling fine, then when i started driving, the tach would jump to 3k and so on....which was weird, i didnt want to mess with it, cause i pulled it from a totalled car that had been pretty banged up in the front...so i just ordered a new cluster from ebay, plugged it in, and everything worked like a charm....so maybe if u know anyone else with a EL cluster, try to plug theirs in your car, and see how that works...if its fine, then just order a cluster from ebay...and u ll be strt8.

94ludefunk · 09-26-2005, 10:47 PM

My tach also reads high. When I read the rpm under the hood the idle is fine. I installed a whole new Moroso Dist. which included all the guts and had no change what so ever. It still reads high exactly the same amount with the new Dist. The tach also jumps up to 1000 when key is in accessory position sometimes.

92preludesi_TX · 09-26-2005, 11:20 PM

^^^^that sounds like the same problem that I am having...

Si_g · 09-27-2005, 12:01 AM

well...i had the same problem and i ve told u what i did fixed it 2 years ago...if you both have tried what i did...then u r better off taking it to honda so they can properly diagnose it...i m out of ideas

LudemanDan · 09-27-2005, 11:05 PM

This has been informative.

Blamo · 03-16-2007, 02:18 PM

i have a 94 and just a couple of days after my brain went out in my alarm (which dosent have remote start) my tach was messed up. See it wasnt high or anything....at idle...it sits at 0. But it NEVER jumps anywhere....it just stays at this low idle. I think its 1600 low, so when im at 3000rpms...it reads 1400rpms. My only test to this is what it would read when i hit the rev limiter. But its never jerked or stuck or acted funny at all, it just decided it wants to read 1600 lower than what your actually at.