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1G Tachometer works on and off

SnowmanFD

Proven Member
130
7
Dec 11, 2021
North Seattle, Washington
I have a 90 talon tsi and the tachometer is almost never accurate when going above 60% throttle or hitting boost. it works fine almost any other time. The previous owner installed a new dash and im think its something to do with that so im wondering what i should do to try and fix it. Also There is and aftermarket boost gauge if that would effect anything
 
Last edited:

1990TSIAWDTALON

Moderator
9,148
4,979
Nov 14, 2013
Independence, Kansas
You need the 90 tach and make sure your tach filter is hooked up and just there period. Its '90 specific.
Aftermarket boost gauge doesnt effect the tach.

This is what it looks like. It is mounted on the intake manifold and plugs into the harness around the PTU area.

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DSMPT

DSM Wiseman
2,003
1,558
Jun 12, 2014
Japan / Mexico, Arizona
Ill take a look for the filter when i get home. Is there any way to tell what year the dash is from?
If yours is 90, you should see the speedometer numbers start from 5mph and 15, 25, 35... If 91-94, you would see the numbers from 0 and then 10, 20, 30...
 

SnowmanFD

Proven Member
130
7
Dec 11, 2021
North Seattle, Washington
So i do have a 90 dash because it starts with 5 mph. I think i found the filter but cant completely tell what it mounts to or what it plugs into 🤔
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SnowmanFD

Proven Member
130
7
Dec 11, 2021
North Seattle, Washington
So after doing some more looking i have what seems to be a 94 ecu according to the part number.
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1990TSIAWDTALON

Moderator
9,148
4,979
Nov 14, 2013
Independence, Kansas
Unless its been "converted" to work in a 90 (swap pins 6 and 14) like THIS thread, it won't work or work correctly.
 

19Eclipse90

DSM Wiseman
5,147
984
Sep 29, 2003
OKC, Oklahoma
So i do have a 90 dash because it starts with 5 mph. I think i found the filter but cant completely tell what it mounts to or what it plugs into 🤔
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Yep, the box is the noise filter. You'll want to bolt that to the intake manifold to ground it. They don't work consistently if they are free-hanging.
The open connector you show is the EGR temperature sensor connector, only used in Cali-spec vehicles.
 

steve

DSM Wiseman
14,482
1,407
Feb 3, 2002
St. Charles, Illinois
Putting a later ECU into a 90 car is more involved than just swapping pin 6 and 14.
You either need one of the old Keydiver Tach Adapters or go through the hassle of sticking a 91+ PTM in to feed the ECU and leave the 90 Tach Gate and Noise filter on the coils to feed the gauge cluster.

Or you coould source a 90 ECU....
 

1cleangsx

Proven Member
661
545
Sep 28, 2013
Cheyenne, Wyoming
If your only issue is the tachometer you can ditch that plug and make a jumper wire to ground out the harness as I showed in my build thread
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We're on Boost

Proven Member
1,446
330
Aug 25, 2007
Seattle area, Washington
Well here's one way to attach it. I got this pic from 19Eclipse90 just last week.
This is not the stock location, but it's grounded metal so it works.
The stock location is under the intake manifold on the manifold "stay". But I don't seem to have a picture of that.

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steve

DSM Wiseman
14,482
1,407
Feb 3, 2002
St. Charles, Illinois
Lets review what pins 6 and 14 do so we can understand the impact. On a 90 harness/ECU pin 6 is for the Idle Position Switch that tells the ECU that the throttle is closed. There are several ECU functions that are driven by the throttle being close, idle speed management, Dashpot emulation, and deceleration fuel cut (which also causes idle surge). Pin 14 is the signal to the MAF to reset it's airflow counters. On the 91-94 ECUs thse pins swapped location.

Will the car run if these are wrong, yes but not well.

Here's the original location where the 90 Noise filter resides.

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Thank you to whomever posted these. (Marty was one of them)
 

SnowmanFD

Proven Member
130
7
Dec 11, 2021
North Seattle, Washington
The brake light on my cluster is on, im thinking its probably because i need new brakes.

Update: i have the 91-94 PT and just need to install it with the pin swapping and noise filter.
I had given up a few months ago because it was lower on my to do list and also i was way to confused.
Question: why does the tach NOT work when i hit boost. But works fine the rest of the time?
 

TK's9d2TSi

Supporting Member
6,318
3,304
Sep 11, 2017
Cincinnati, Ohio
Would this also cause the brake light on the cluster to be inaccurate?
There are two thing that cause the brake light on the dash to eliminate.
1. The hand brake.
2. Low brake fluid in the reservoir.
 
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