My 1993 Mazda MX-3 GS is running rough. (2 days ago) I start it and the rpm's bounce, then going in first gear is jerky. I look like someone who can't drive stick. (today) first and second gear is now jerky and it cut off on me four times on my way home. It cuts off after I stop moving and the rpm's gradually decrease to zero. Can anyone help me. Thanks in advance.

 

First guess: cracked air intake hose. Use duct tape if you find cracks.
second guess: other vacuum leaks.

 

How do you test for a vacuum leak?

 

Youtube "how to find vacuum leaks" by "scottykilmer".

Inspect to find cracked hoses, loose connections hardened rubber hoses.

Idle the engine and listen for a hissing sound. Remove a small vacuum hose so you know how that might sound.

cover suspected areas with with plastic film.
Spray some WD 40 or water at suspected areas, DON'T SPRAY ANY SILICONE, IT WILL COAT THE O2 SENSORS! The WD 40 or water could close the leak for a short time and thus improve the idle.

Use an enrichment tool. I. e. a propane torch with a rubber hose attached to it. Idle the engine, open the torch and place the rubber hose at the suspected areas. When the idle changes it sucks in the gases through the leak.

 

In the world of General Aviation looking for intake leaks is something that comes in handy for running engines leaner than stoichiometric; as such we've come up with a fairly easy method of searching, and this method is easily applied to cars as well.

To search for a vacuum leak:

• Completely duct tape the exhaust pipe(s) so no air can escape
• Duct tape a compressed air source to to the engine air intake at or just upstream of the throttle body
• Fill a spray bottle with soapy water
• Engage the compressed air source at a low pressure of only a couple of PSI
• Spritz the soapy water all over the entire network of intake and vacuum plumbing

When vacuum leaks are encountered you will see bubbles being generated at or near the leak(s).

 

Shipo, I love it! My whole neighborhood will come over and ask if there is something wrong with my washing machine!

 

Late on the reply but thanks. Duct tape fixed it and haven't had a problem since.

 

Thanks for the feedback! Duct tape, the best invention since sliced bread!