tach stops working after 4000

maddog_187 · 05-02-2008, 08:05 AM

Can some one help me out? My tach acts funny after 4000 rpm's sometimes bounces around but if i give it full throttle it goes to 0 rpm's! Any ideas? I just finished a rebuild of the engine so I could have screwed something up but not for sure. Could a dsm chip cause this? Even in low rpm's it bounces around a little! Another question can a couple of people give me there speeds at 7000 rpm's for each gear until i get this resolved I will watch how fast i'm going in each gear. I know 5th my be a little harder for some because if I remember right it's around 160+.

Thanks for help guys

DoItOnAll4s · 05-02-2008, 09:49 AM

Is it just your tach that's gone insane? I take it your engine runs properly? Usually it's due to a small error, like forgetting to connect a cable or wire, loose wiring. Could check the wiring inside the gauge cluster too. I had an issue with that on an old hyundai. My friend had an issue with his tach not going past 3000 just cause he forgot to reconnect his MAF sensor on his subaru.

maddog_187 · 05-02-2008, 10:04 AM

I've checked all the wires and they are plugged in. The engine runs fine I've put a 100 miles on it since the rebuild.

turboglenn · 05-02-2008, 10:09 AM

Are you using an MSD ignition? There's a few people around here witht he same issues after a local shop put in their DIS-2 and tach adapter. Also how's your abttery voltage and alternator?

shuedaman · 05-02-2008, 10:34 AM

Are you using the stock transistor pack? My tach acted like that before my transistor pack failed. Check the connection, sometimes a wiggle in one direction will make it go away. Be prepared to replace the power transistor in the near future.

maddog_187 · 05-02-2008, 10:49 AM

No msd on the car. It is the stock transistor though I will try to wiggle it and see if anything happens.

maddog_187 · 05-02-2008, 10:50 AM

battery and altenator are fine also.

FFTEC · 05-02-2008, 10:59 AM

An issue similar to the one you are describing happens when a 1991-1994 ecu is used in a 1990 car. Just a possibility

maddog_187 · 05-02-2008, 11:05 AM

That is a good idea let me check that I just bought a new eprom while the car was down. It came with no case so I will have to open it up to check the numbers.

maddog_187 · 05-02-2008, 03:57 PM

You hit it right on the head the ecu is for 91-92!!! I'll add that to the list of things I got screwed on in this deal. What is the easiest way to fix it now. Swap pins 6 and 14 and what else do I have to do to make the tach work?

FFTEC · 05-02-2008, 05:02 PM

Glad to help

You can either convert the ignitor and gauge cluster to the 1991-1994 or swap the ecu. Either one will fix your issue.

relmer4 · 05-02-2008, 09:52 PM

dsmchips.com makes an external and internal kit to use the 91-94ecu in 1990 cars without the need to swap the cluster and/or ignition components. You will still need to swap pins 6 and 14http://www.dsmchips.com/1990ecu.html I don't know if the link will work, but a copy/paste should. I'm thinking about using the 91-94 e-prom ecu because there easier for me to find. Hope this helps.

maddog_187 · 05-03-2008, 01:07 PM

Okay got the 6 & 14 pins swapped! Now getting a tps error!!! Do you think running the 91 ecu would have caused it to go bad or do I need to adjust something?

Thanks again for the help guys!

KB90TSIAWD · 08-12-2012, 10:01 PM

hey finally got a thread im lookin for. i have the same issue. 90 car and 91 ecu. tach is RETARDED. was told a few options. One was to jus take out pin 109. but heard about the dsmchips and their internal and external kit. Im thinkin to go with the external ### im no computer geek. Have you tried to go with this. i would like to see some pics if anyone has.