1994 Mazda rough Idle

My 1994 Mazda B3000, 3.0l Ford “Vulcan” v6, 54,000 miles (yes on a 1994!), is being a major PITA lately… Every morning when I go to start it up, it will start up, run ok for about 2 seconds, then all of a sudden run very rough, around 200 RPM, then stall and die. If I start it again, it always starts up and idles, but for the rest of the day it idles without stalling, but it idles rough and shakes quite a bit. When I drive it, it’s virtually powerless, feels like I’m driving a Metro Geo again… It’s also been guzzling gas, my 3.0 is turning a steady 13mpg :frowning:

Here’s what I know / have done…

-Brand New 02 plugs (didn’t help)

-Cleaned MAF sensor connections (didn’t help)

-Reset computer (didn’t help)

-Seafoamed engine through gas tank, oil, and brake booster

-New plugs, new wires, cleaned distrubetor and cap…

I live in a very small Texas town and can’t find anyone that can pull codes from a 1994… So that doesn’t help me… Any suggestions?

I’m going to go out on a limb and say timing chain. If it wasn’t drinking fuel at such a large rate, I might blame the fuel system (might have the pressure at the fuel rail checked, just for the heck of it), but this has all the classic symptoms of timing being out of whack. Either the chain is off a tooth or it’s just got too much slack in it.

Did this just start all of a sudden or did it occur after another event?

A 1994 will not have OBD2 diagnostics, but it probably has a shorting-wire-in-the-diagnostics-connector-and-read-out-the-code computer read out. You may have to do some internet searching or check a manual to find out how. I don’t know if the Haynes manual for the B3000 will tell you how to read the codes. The one for the Protege-323 does (Section 6.3 – not especially easy to find given the crummy index). Is the CHECK ENGINE light on? Unlike OBD2, there very likely is no point in checking codes if the CE light is not lit.

Overall, it sounds to me like one or two cylinders aren’t firing, but I’m not really an engine guy. You could try unplugging spark plug wires systematically. If the engine runs even worse or not at all with a given wire unplugged, that cylinder is probably firing. I suppose a compression check on all the cylinders won’t do any harm and might tell you something.

Well, forgot to mention that I pulled all the plugs and they all looked fine and a little worn as if they had all been firing… Can I get more info on the timing chain? What’s a good way to test it, as my engine doesn’t have any timing marks? (I’ve looked before)