Rough idle and stalls when stopped

JEREMOBDICC

MEMBER
1992 FORD MUSTANG
2.4L
4 CYL
2WD
AUTOMATIC
83,000 MILES

Hey guys, so I drive the car listed above. About two days ago I noticed that my car all of the sudden has 4 new problems: it idles real rough. When I start it, it kinda sits at 1,000 rpm's like it does usually and I wait about 30 seconds and the rpm needle just kinda bounces around 1,000 until it stops. It does this at red lights and stop signs too. I initially think that it can’t be the alternator because I bought this car 3 months ago with a “brand new alternator “. I also noticed that my mpg is really bad :/ I get about 8 mpg and my car kinda smells like gas. There is no check engine light on. I’ve asked a few of my contacts and they say that it could be a vacuum leak? Maybe? I would also like to add that it revs really high from first to second gear. Basically my question is, could there be a vacuum leak?

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

Short answer is yes. I attached a guide that will help with this.

Each of those points to a vacuum leak. If you have a vacuum leak you can put a vacuum gauge on it and tell in two seconds. If you don't have a gauge, you can pick one up at a parts store for less then $20.00 in most cases.

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

Otherwise you can follow this guide to determine if you have a leak. The gauge is more definitive because sometimes people don't find the leak using this method and assume they don't have a leak, even though they do. They just didn't find it. With the gauge we know we have a leak then it just becomes a matter of finding it.

Let us know if you have questions. Thanks.