Tachometer inconsistancy
Thread Starter
Burning Brakes
Joined: Dec 2007
Posts: 805
Likes: 3
From: Waco TX
Tachometer inconsistancy
I notice my tach (the stock one, not an aftermarket bolted on the A-pillar) doesn't alway read the same # for the same speed.
For example, I have my cruise set on 65mph, and it may read right at 2000rpm. I slow down and speed up again and reset the cruise at 65mph again, it might read about 2200. If I do it again, it'll read a different #. Put short, its always + or - very roughly 200rpm for the same speed.
Is this something to be worried about? The car shifts fine-nothing weird or odd about the shiftpoints, etc.
It should be noted that I have a VERY SLOW leak from my transmission I need to get look at. That could be totally unrelated.
Anyone have this problem?
For example, I have my cruise set on 65mph, and it may read right at 2000rpm. I slow down and speed up again and reset the cruise at 65mph again, it might read about 2200. If I do it again, it'll read a different #. Put short, its always + or - very roughly 200rpm for the same speed.
Is this something to be worried about? The car shifts fine-nothing weird or odd about the shiftpoints, etc.
It should be noted that I have a VERY SLOW leak from my transmission I need to get look at. That could be totally unrelated.
Anyone have this problem?
Advanced
Joined: Feb 2008
Posts: 71
Likes: 0
From: Hell
Its just a voltage inconsitance due to the wireing getting old. I would not worry about it as long as everything else seems fine. if you want to fix it trace back the wireing and look for breaks and contact in the casing.
Thread Starter
Burning Brakes
Joined: Dec 2007
Posts: 805
Likes: 3
From: Waco TX
Okay, I do notice the volt meter gauge sometimes does flicker back and forth and the backlights brighten and dim in synch with the needle on the volt gauge jumping around. Any chance its a bad connection somewhere?
Safety Car
Joined: Feb 1999
Posts: 3,504
Likes: 4
From: Mexico Beach FL
If you have an automatic transmission, you may be looking at the tachometer with and without the torque converter clutch locked up.
The rpm will drop about 200 rpm when the TCC locks and eliminates torque converter slippage.
Tom Piper
The rpm will drop about 200 rpm when the TCC locks and eliminates torque converter slippage.
Tom Piper
Melting Slicks
Joined: Jan 2008
Posts: 2,054
Likes: 120
From: AZ
My car is a 4+3 and I discovered rather early that the digi-tach is not too accurate. The numbers don't even agree with the pretty color line.
Thank goodness for rev limiters, or in the stock engine, the teensy ports in the intake.
Thank goodness for rev limiters, or in the stock engine, the teensy ports in the intake.
Thread Starter
Burning Brakes
Joined: Dec 2007
Posts: 805
Likes: 3
From: Waco TX
If you have an automatic transmission, you may be looking at the tachometer with and without the torque converter clutch locked up.
The rpm will drop about 200 rpm when the TCC locks and eliminates torque converter slippage.
The rpm will drop about 200 rpm when the TCC locks and eliminates torque converter slippage.
OMG. Tell me that's something cheap and easy to fix. Last thing I need is a $1000+ dollar fix on this car.
Safety Car
Joined: Feb 1999
Posts: 3,504
Likes: 4
From: Mexico Beach FL
Then, while holding your right foot on the accelerator and keeping the speed constant, very lightly put your left foot on the brake pedal and push down enough to disengage the torque converter clutch without applying the brake -- and then, notice the tach reading again.
It is normal for the tach to increase by about 200 rpm when that clutch is disengaged and then to decrease by 200 rpm when it engages again when you take your foot off the brake.
Usually, when the torque converter clutch goes bad, you will feel a "shudder" when making the vehicle pull lightly at highway speed. When that happens, the only way I know to fix it is to replace the torque converter.
Tom Piper
Last edited by Tom Piper; Feb 10, 2008 at 07:18 PM.
