1991 Mercury Cougar Check Engine Light

1991 MERCURY COUGAR
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PYRORAVEN
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  • 1 POST
The check Engine light is on, first I check all the fluids and the levels are fine, then I took for a test drive and it will idle fine, a little rough though, when I press on the accelerator, the check engine light goes out briefly, but then comes back on and the engine looses power or dies, but when the accelerator is released sometimes it will return to a rough idle, i can lightly press on the accelerator and it will go, but as I try to go faster the same happens again. This continues in Reverse as well as Drive. Any help in an idea of the possible diagnosis would be appreciated.
Jul 9, 2006 at 1:56 PM
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KASEKENNY
  • ✓Experienced Mechanic
  • 18,907 POSTS
There are a few things that can cause this so we need to start with checking what codes are there as that will tell us what system we need to diagnose.

Here is a guide that will help with this:

https://www.2carpros.com/articles/ford-lincoln-mercury-obd1-1995-and-earlier-diagnostic-trouble-code-definition-and-retrieval

This could be a vacuum leak, but the codes will give us more detail. In the event we do have a lean code, which would indicate a vacuum leak, then here are a couple guides that will help with this:

https://www.2carpros.com/articles/engine-has-low-power-output

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

Please run through all this info and let us know what questions you have.

Thanks
Mar 22, 2022 at 2:22 AM

Suggested Repair

Retrieve the OBD1 diagnostic trouble codes first to identify the affected system. If a lean code is present, inspect for vacuum leaks and follow lean-mixture diagnostics.

Conversation Summary

The owner of a 1991 Mercury Cougar reports a check engine light, rough idle, and power loss or stalling under acceleration in Drive and Reverse. Fluid levels were already checked and are fine. The expert advises retrieving diagnostic codes first and notes a vacuum leak is possible if a lean code is stored.

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