I have a 1993 Mazda MX-6. For the past 2-3 years, my car shudders when it idles or goes less than 10 miles an hour. More and more lately, it has been shutting off completely when I drive slow or come to a stop. The first few weeks it was happening, one day while in a Burger King drive-thru (of all places- how embarrassing), it shut off and I couldn’t get it to start again. The mechanic I took it to replaced the distributor to fix it. It has not had a problem starting anymore since then, but it still shudders very hard. Could it be something else that’s wrong?
I have also discovered that turning on the air conditioning helps the RPMs to stabilize, and the higher I turn the A/C, the more power it seems to get. Don’t know if that is related.
How old are those spark plugs & wires? Air & fuel filters? Your car is just running a little poorly. The first thing to deal with is making sure basic maintenance is all up to date.
I’d also clean (or have cleaned) the idle air control (IAC) valve and its port on the intake. This should be a cheap & easy thing to do. It sounds like a good possibility that yours is a bit gummed up. The thing about the A/C is that it puts a hefty load on the engine. The engine’s computer will compensate, partly by opening up the IAC to allow more air. A little bit of restriction might be affecting air flow at regular idle, but the little bit of change with the AC on may end up compensating for it.
Someone should also check your fuel pressure.
Thank you, I’ll look into those things!