Erratic Tach and Check Engine Light
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Elder User
Joined: Feb 2003
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From: Coleman, Wisconsin
Erratic Tach and Check Engine Light
I have a 1990 Ranger XLT 2.3L and about once a month the tach goes erractic and sometimes stays around 200rpm and at the same time the MIL will flash. The truck runs fine when this happens and it usually only lasts a day or two. I have never heard of or seen this happen before and I could use some assistance in correcting the problem. Thanks for any help.
Post Fiend
Joined: Jan 2003
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From: Connecticut
Former ******
Joined: Nov 2004
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From: Salt Lake City, Utah
Several things could be happening. Your tach signal is derived from the tach terminal on the ignition module. This module in turn gets its signal from the pickup coil or PIP signal inside the distributor. Any interruption in the wiring, connectors, or the sensors can cause misfires. The module itself can also have problems. The coil is triggered by changes in the magnetic field, ie, when the field is formed or collapses, it drives the secondary coil and triggers high voltage to arc. Any interruption in this process will result in a no spark condition.
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Joined: Jan 2004
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From: SW Va
I like Rockledge & BearRiver's ideas & add distributor bearing wear to your suspect list.
You can pull the computer trouble codes yourself, by following instructons in the "Tech Info" thread, atop this forums thread listing page, if your autoparts store doesn't use a scantool that'll hook up to your OBD-1 under hood diagnostic connector.
The computer trouble codes can offer up good trouble shooting clues, so post ALL of the code numbers found.
If you come to suspect the distributor or it's attached ignition module, they too can be bench tested at most autoparts stores at no cost.
More thoughts for consideration, let us know what you find.
You can pull the computer trouble codes yourself, by following instructons in the "Tech Info" thread, atop this forums thread listing page, if your autoparts store doesn't use a scantool that'll hook up to your OBD-1 under hood diagnostic connector.
The computer trouble codes can offer up good trouble shooting clues, so post ALL of the code numbers found.
If you come to suspect the distributor or it's attached ignition module, they too can be bench tested at most autoparts stores at no cost.
More thoughts for consideration, let us know what you find.
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