Engine light is on

PYRORAVEN

MEMBER
1991 MERCURY COUGAR

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.

1 Reply

KASEKENNY

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