Spaceman

My 91 has had problems idling with the a/c on since I bought it a few years back. It did fine when the outside temp was cool (below 80) but on hot days it stalled at idle with the a/c on unless I gave it a little gas. Everything I've read in the FAQs and everyone I've talked to said it's most likely a vacuum problem, likely the BAC. I went over the whole system, component by component, and couldn't find a thing.



Lately the idle has gotten worse. Even with the a/c off the idle is strange. The fast idle when I first start it in the morning is normal. However, as soon as the engine starts to warm up the idle hunts between about 1200 and 1500 rpm. That's in the morning, when the air is cool. Later in the day when the engine is fully warmed up and the outside temps are in the 90's the idle hunts between 600 and 800 rpm.



I took it to my local Mazda shop and they claim it has low compression. They'd be more than happy to rebuild it for me. The thing is, I can't feel any difference in response since the idle problem got worse and it seems to have pretty good pickup. If I really have a compression problem shouldn't I be able to detect something out of the ordinary when driving it, other than just the funky idle? If I'm willing to live with the idle problem, what happens if I keep driving it without a rebuild?

mazdadrifter

try to wiggle the electrical connection on your bac valve. my connector came apart and it had a similair problem.



or you could just unplug the connector and resoder it to remove that as a option.



the bac is actually what adjusts your idle when you turn your a/c on or when your p/s pump but extra stress on your motor



if it were a vaccum leak you'd probably have an idle problem 100% of the time, unless it was just a slight leak.



my car has over 200k on it, and hasn't started on it's own when warm in about 6 months. (low low compression), but still holds an idle fine (although it isn't as smooth as a new block)

Cosmo Donk

TPS might be out of whack as well.



Mazda dealers are retarded. They don't know anything so they just want to replace the whole engine.



You can also do the WD-40 trick. With the car running spray around the vacuum lines and see if the idle goes up. If it does, you have a leak.

mpfinn

had same problem with mine, engine failed soon after (my fault lack of oil); replaced engine and all hoses; works great now,so i would suggest trying to change hoses first

Spaceman

Thanks for all the replies. I've just moved to Southern CA from Puerto Rico and now have access to lots of shops. I've learned my lesson about the dealers; thank God I didn't have to learn the hard way by having a new engine dropped in. Funny thing is when I asked the dealer service shop if they were comfortable working on rotary engines they said "of course, the RX8 is rotary so our guys know this stuff perfectly". I'm not settled in yet, but once I get moved into my house and all my tools arrive I'll take another stab at the BAC and other likely components. If that doesn't work I'll try Mazdatrix in Long Beach. They only do RX7's so if they can't find the problem there's no hope.