mlow

My 99 miata started blinking a CEL at me the other day, while I was driving. I didn't notice any misfire at first, but it quickly got worse, within two minutes. To get back to work I had to rev to about two grand and abuse to clutch, to keep it from stalling.

It would appear to only be running on cylinders 1 and 4, as pulling plugs 2 and 3 didn't affect the rough idle. I replaced my plugs and wires, to no effect. Then I ordered a coil pack, installed it, and the car will barely start at all, and won't idle for more than 10 seconds or so. When it does manage to start, it's rough, then it ups the idle to ~1900 rpm fairly smoothly. Add any throttle and it chokes, shudders, and dies.

I'm basically at a loss as to what the next step would be. It's been suggested that my ECU might have dropped a channel, but that sounds extremely unlikely. A stuck injector has also been suggested, but since I got a misfire code, it doesn't seem likely, either.

Arkmage

iTrader: (3)

Alright guys.... please help this guy out... he's a friend of mine and needs his car to get to work (already missed 2 days). I've tried but we have reached the end of my usefullness as a diagnostician.

budget racer

iTrader: (1)

Have you done a compression test to see the integrity of the cylinders? could it be a blown head gasket between cyl 2 & 3?

m2cupcar

iTrader: (5)

Pull the plugs, stick them in the wires, lay the wires on the valve cover so the plugs can ground on the valve cover. Crank the car breifly to check for spark at each plug. You can unplug the injector harness to keep from washing the cyldiners with fuel. But, if you leave them hooked up, you'll also be able to sniff the cylinders for fuel.

You may also be able to manually rotate the crank with a wrench and the ignition turned on to do this procedure. I know the NA will let you do it. Then can verify each injector is triggering and each plug is sparking.

Check for the actual injector/ign events and check for proper pairing of events for each cylinder.

steelrat

Also you should get a code reader and see what the stored codes are.

Other possibilites will be fuel or spark as others have suggested.

You can put a long screwdriver on the injector, to see if it's firing -- you have to listen to the screwdriver -- like a doctor. <G>

Check for spark for sure, especially if you have done the coils and plugs/wires...

Check your TPS/TB/vac leaks. Make sure you TPS is plugged in, etc. ALso check for vac leaks, and stuff like that. Maybe you should give the TB a quick clean too.

Dave,

akaryrye

iTrader: (5)

Definitely verify that it is:
1. sparking by pulling the plugs out one by one and grounding them against the valve cover with a friend cranking the car
2. Check that the injectors are firing
3. Check the timing if you can get it to idle somehow, i dunno how this all works on a 99.

Since you have replaced the plugs, wires, and coilpack, you have replaced the entire ignition system short of wiring and ecu. I think it may be either an ecu issue and if I had access would definitely plug someone elses in, or an RPM triggering issue (meaning the ECU would be getting erroneous RPM values)

Could someone with a 99 chime in with how the 99 ECU reads RPM? I know in a 90 - 97 it uses the cam angle sensor, but doesn't the 99 and up use a crank angle sensor instead? Is it possible that the crank wheel or keyway or whatever has been damaged, causing the timing to be way off?

Anyway, its just some thoughts, methinks it sounds like your timing is way off for whatever reason.

steelrat

There was a local guy who had the motor replaced for the #4 bearing issue. Motor #2 turned out to have a bad crank. It was actually bent. If you watched it, the crank pulley would move a little (aka like the short nose failure). This ment that the timing wheel would move away from the sensor.

You should check the pickup for the timing wheel, and make sure that it's reading OK. The code he was getting was a random misfire, or something like that...

Dave,

Arkmage

iTrader: (3)

Alrighty guys... the problem may have been been gas. I haven't talked to him today yet, but when I talked to him last night he said something about draining a gallon or two of water out of the gas tank.

Be careful where you get your fuel!

Arkmage

iTrader: (3)

Is this default answer around here? as he stated the problem cropped up almost instantly... compression issues come up slowly and head gasket issues don't normally make the car run that poorly (just makes it over heat quick).

I see "do a compression check" come up as an answer far too often around here... it's kinda aggrevating.

*edit* to only offend those that suggest compression checks when not needed