veedubbed

EDIT - I got into this a little more than I had planned when I first wrote it, so the title is a little misleading.

My car has a slight misfire everynow and then at idle. I have a few theories on why this is, but here's what the car does in detail.


Idles rock solid at 750 RPMs with a slight misfire every say.... 15 seconds. I had a timing light on the car today, and noticed that whenever a misfire happened, the light didn't fire. The car has new plugs and new wires. Could this be a coil issue?

My boost gauges reads 12-14 inHG at idle. Motor makes very good compression, so I obviously have a leak somewhere. Only thing that isn't new seal/gasket wise south of the TB is the injector grommets/orings. I have new ones on the way from Mazdatrix - we will see what that does for me. The ones in there right now are rock hard, not sure if they would cause much of a leak though. I am also planning on checking the TB for leaks while it is off.

The car also has other idle problems. When I start it in the morning, and the ECU takes over with cold start enrichment, at any RPM above 1100, it will misfire constantly. This also happens if the car is warmed up and I hold the RPM's anywhere between 1100-2000. It is a very rapid and random misfire - not just on one rotor or the other.

When I am slowing down for a stop light, and clutch-in, the car will do one of two things. It either falls to 1100 RPM, and gets hung up on the timing advance, starts the rapid misfire process, and will not drop to 750 RPM until I bog it down by putting the car in gear and letting the clutch out a little, then it idles fine. If it doesn't do that, the RPM's fall to ~500, and the car acts like it wants to shut off. It will do this for 10-15 seconds, then make its way back up to 750 RPMs. I have noticed on pattern as to when the car will do either one, it doesn't seem to favor either method. Every now and again, it will fall to 1000 RPM's, hang there for a second, then fall to 750 like it should, but that's pretty rare for it to do that.

That's about as descriptive as I can get with the problem. I have a notion that my vacuum leak is causing some of this, but my primary injectors are stock 550's with 115,xxx miles on them, and I would bet money that they leak due to flooding problems. I read, through searching, that someone had the exact same rapid misfire problem between 1100-2000, and they replaced their injectors, and the problem disappeared.

I am really just looking for opinions on this, because I have been trying to track down this issue for a month or two now, and it's driving me crazy. The car runs really, really good otherwise, just need to get this idle under control. Thanks for your time.


P.S. - Autometer digital boost gauge for sale. 30 inHg to 15 PSI. Phantom series. Includes everything, $50 + shipping.