wAnKeLiSgOd

'84 SE, 52K miles, has been my most reliable car until yesterday. Tried starting the car, wouldn't start. Pulled plugs. Flooded. Bought new plugs. Turned the motor backwards with old plugs out to get rid of excess fuel. Installed new plugs. Still won't run. Pulled new plugs, appeared the leading weren't firing. Didn't confirm this however. The leading plugs looked like new just wet with gas. Got out the ohmmeter, did a reading on the coils, both were about 2.9 then dropped to 2.2. Both about the same. I thought ignitor. I have spares that I know are good because I made the testor. Replaced both.
Tried starting again. Still won't fire up. Held the gas pedal to the floor and it started. It began backfiring, blue smoke galore, then Idles fine. No miss at idle. As soon as I touch the gas, I get stumbling, popping, it won't rev at all. As soon as I let off the gas, it returns to perfect idle. No missing, smooth idle.
Pulled off the throttle sensor, did the ohm test, checked out fine. Reinstalled throttle sensor. Hit the key the car fired right up. Still won't rev. Unplugged the throttle sensor, no change beyond idle. Very rich exhaust. Opened up the air cleaner, the flap is free. Fired it up tried feeling the intake hose for leaks, none. It doesn't seem like a leak there because it idles fine. No vacuum on either distrib advance at idle, as soon as I bump off idle I have vacuum on both hoses.
Pulled the BAC elbow hose off it stalls as it should, put my thumb on it but there isn't much air coming out at Idle. Can't really get steady rpms above idle to see if more comes out. Unplugged the vent and vacuum solenoid valves no change.
This car has had one issue that happened twice in the past 6 months. I'd be driving along and all of a sudden, the car wouldn't go past 3K rpm. It would just die above that. Like it was going to stall then I let off the gas and it bounced back. Up to 3K it was fine. So I went on to work. First time this happened it was raining so I figured electrical. Parked the car at work and by 5 p.m. it was fine. Ran normally. Couple months later on a beautifully sunny and dry day it did it again. Drove it to work, when I went to lunch a few hours later it was fine. WTF it was I don't kno but I suspect whatever it was it failed.

I can pull the air metering unit and do the ohm tests tomorrow on that. I'll try switching the coils.
Any other ideas?

mjm4jc

Fuel system.

mazdaverx713b

iTrader: (91)

are you sure you are getting adequate fuel to the engine? i know that it had flooded but it could still be a filthy fuel filter, allowing enought gas through to allow the engine to idle but nothing more. you can test the afm on the car per the fsm. i would start there. the smoke and backfiring are due to the flooded engine clearing itself out. where in OH are you located?

74RX4

iTrader: (10)

If you haven't already done so, I would replace the fuel filter.

rx-7ames

iTrader: (1)

Replacing the fuel filter is pretty cheap and can't hurt. You can also check the fuel pressure per the FSM. It's really easy. If that doesn't check out then you can try and replace the coils but that probably isn't the problem. If you don't have a spare coil then you can always just buy an MSD coil for the leading and swap it out with the stock coil. It will be worth it even if it doesn't fix the problem.

wAnKeLiSgOd

About two years ago, 8,000 miles ago, I went through the car and among other things did the following: Got a new gas tank from Oregon, had it dipped at Radiator shop, replaced the internal and external fuel filters with Mazda replacements. The tank was spotless inside. I replaced the fuel pump, and I recollect removing and cleaning the cone inline filter there.
There are no CATS on the car. I took them off and replaced with a racingbeat pipe.
I am crossing my fingers that's it's as simple as a failed vaccum hose going to the regulator or from the regulator valve in the rats nest. We'll see.

wAnKeLiSgOd

Where can I buy an MSD coil, what part number is it?

bstrange99

+1 on the fuel filter. Your tank may be new, shiny, and spotless, but the gas stations may not be. Who knows what you're pumping in there.

rx-7ames

iTrader: (1)

MSD Blaster II coil. Don't know the part number off the top of my head but advance auto usually has at least one in stock. It is around $45.

wAnKeLiSgOd

Well, the plot thickens. Switched the coils, checked the fuel regulator switch in the rats nest. Checked the vacuum line from the regulator to the rats nest, all appeared/checked fine. Pulled the plugs again, the trailing looked a little used, the leading appeared as if they weren't really firing, or barely firing. So, just for ***** and giggles I turned the key and she ran fine.
So, I've either got in intermittent that switched itself off, or the leading coil was bad even though it passed the ohm test. I've been driving all day and no issues so far. Can a fuel problem switch itself off? Can a filter unclog itself? I'm going to get some MSD coils just to be sure. Very bizarre.
If the leading coil was bad, however, that means the trailing plugs really aren;t essential???

rx-7ames

iTrader: (1)

It is weird how some problems will switch themselves off. it seems like it might be that coil though. Also, the trailing plugs aren't totally essential. Your car should run without them although it will run much better with. The trailing plugs help emissions by burning off any extra or left over fuel that didn't combust with the initial spark. That is why I suggested replacing the leading coil, because you don't really need to upgrade the trailing, although it doesn't hurt.

Good luck with the car. Hopefully it keeps running well. Keep us updated on your situation.

wAnKeLiSgOd

I don't entirely get it, but I'm sourcing a couple MSD coils. 90,000 volts should be enuff to fire the plugs, eh?
I suppose when/if this happens again I can assume the coils aren't going to be the culprit. I like this car, it's more reliable than my X5. That piece of **** left me stranded three times in two years. Twice for the same thing. This little Mazda is one helluva backup car. It didn't leave me stranded either. This issue happened right in the driveway. Best place to break down. So, we'll get some coils and go from there.

mazdaverx713b

iTrader: (91)

whereabouts are you located on OH?

74RX4

iTrader: (10)

Looking at the plugs and guessing whether or not they are firing is useless. You need to test whether or not they really are getting spark. Stock coils are not an issue very often. I would think a failing ignitor or bad rotor are more likely. How old are the distributor cap and rotor? Check the terminals inside the cap for wear.

The static ignitor tester does not guarantee a perfect ignitor. Someone else verified this in a thread recently. 2 years 8000 miles....I'd be under the car changing the filter if it were mine. I'm not sure that's the problem, but can't hurt, it's cheap, and your symptoms fit.

wAnKeLiSgOd

Of course you are correct about the spark. But as I am one person, and don't want to try jumping the starter and checking the plug wires for spark all at the same time, I had to use my eyes. Switching the coils was just a shot. A cost-free and easy thing to do just to see what happened, if anything. I did check the cap for cracks, wear, etc. I didn't see anything that would cause a catastrophic failure such as I experienced. I did change out both ignitors with tested good ones. Since the car did not improve or change, that would suggest the ignitors weren't the problem.
If the coil thing didn't work, the next step would have been to get out the pressure gauges and see what was coming from the fuel pump.
Fuel filters don't unclog themselves. The original one was factory--20 years old and 43,000 miles---and it wasn't clogged. But going over the car, it was one of the items on my to-do list. I replaced it with a new factory one ($35) 8,000 miles ago. Replacing parts just to eliminate them as a problem is an expensive way to repair cars. If you are running a shop like that you lose money, quick.
So far, this hasn't cost me a nickel. I'll switch the coils again to see what happens before I buy the new one. This is definitely an interesting discussion.