IcantDo55

iTrader: (11)

2000 5-spd
90K No cat so I expect the CEL for cat.

New. wires, plugs, Coil pack,

Bought the car in Florida, flew down and picked it up, drove it 1,000 miles home with no issues, now a month later I'm having some. CEL came on (blinking)and car was missing "P0304" after much searching I replaced the wires and plugs and same issue. So bit the bullet and spent the $300 on a new Mazda coil pack. Worked well for 200 miles and now missing again and CEL blinking again. WTF?

Only other codes I got were P0420 Because cat is missing and P171 lean condition.

I have plenty of experience with cars and it sounds like it is running on two cylinders.

Where do I start looking?

Compression is 170-180 across the four.

I know...I know just MS it, I have an MSII here ready for install but I want to know the car works stock before I change things. MS coming soon.

miatamania

iTrader: (9)

Nvm.

saedrin

iTrader: (2)

Start pulling plug wires while its idling and narrow the misfire down to each cylinder.

IcantDo55

iTrader: (11)

Did that sounds like #4

But #1 seems to work? And its the same coil

elderc

I had the same three codes due to no cat (although it took a few months for all three codes to come on) I did this 1,500 miles ago to the rear 0/2..... "no codes" at all this will fix it:

O2 Sensor modification using spark plug non-foulers

IcantDo55

iTrader: (11)

Was it missing and running on 3 cylinders? I can pull wire off # 4 and it runs the same, bad! How would an O2 cause # 4 to not fire?

elderc

Mine was missing and running like crap, P0420 code in the 1999-00 shop manual lists (front & rear 0/2 sensor) P0304 also lists 0/2 as possible cause. If you have no cat and the rear 0/2 sends no changes in information to the ecu after a while the ecu starts freeking out ( mine took almost a year before I started getting strange codes) and starts trying to adjust other stuff. I replaced a lot of parts I did'nt need untill I spoke to a Mazda Tech. with 30 years exp.
he told me if I was not going to run without a cat I would need to trick the ecu into seeing a signal change from the rear 0/2 or I would always get those messed up codes....................so from a Honda guy I got the 0/2 sim. trick.
NO MORE CODES ! Just broke the 2,000 mile mark (with 0/2 mod) still no codes where as I would get a code after 10-30 miles of driving .

Stephanie Turner

If you are still misfiring after replacing coils, wires, and plugs - about the ONLY OTHER THING that can cause a misfire is a clogged or open injector. Hence, in your case, the lean condition. A missing catalytic converter will not cause the engine to misfire. The engine throwing a CAT below efficiency code will not cause it to misfire. Pull the injectors and take them somewhere to be cleaned. Or replace it.
Stephanie

elderc

Stephanie,
I was also getting a lean code but my A/F's would dip into the 9's-10's (not lean) @ 6% tps @ 60mph under a noload condition and that would cause my spark plugs to foul out which would cause a misfire code. I put this information out because I fought this for almost a year, new 0/2's, Maf, coil pack, wires, plugs, boost sensor, had my injectors cleaned and flow tested ....etc......
I had all the same codes at the same time the car was almost not drivable.
Its a $5.00 fix or at least it was for me.

IcantDo55

iTrader: (11)

So far I have replaced:

Spark plugs twice
Coil pack
Wires twice
Added O2 "spark plug anti-fouler mod)

Still getting P0304! Misses bad at idle and part throttle cruise but under WOT seems sooth.

Stephanie, can bad injectors cause this CEL? How?

What next?

saedrin

iTrader: (2)

That spark plug mod better not be on the first O2 sensor.

IcantDo55

iTrader: (11)

Nope it was on the back.

IcantDo55

iTrader: (11)

So I think I might have solved it :::fingers crossed::: it ran flawlessly for an hour today and a 10 mile drive so I have my hopes up. I kept thinking how does the car know its P0304 and not P0301, they are the same coil...so I got checking the crank position sensor and according to all the reading I have done it needs to be .020"-.059" from the crank, mine was .090". I moved it closer and no more CEL so far.

So what does this mean, I probably just bought a set of wires, plugs and a $250 coil pack for no resin.....great!

Toddcod

iTrader: (8)

This may sound like a dumb question.

What do your plugs look like when you pull them? Do you have oil on the bottom of the plug wires.

I had a valve cover leak, and oil kept getting into the plug shaft, and making the plug missfire.

Pull the plugs and if there is oil in the shaft. Pull the plugs, let the oil drain in. and start it. IF the new plugs fix it. Get a new valve cover gasket.

They cause simptoms like this all the time.

But I have had no codes, since I drive NA.


If there is no oil, never mind me. LOL

IcantDo55

iTrader: (11)

No oil in there, the VC gasket is new and not leaking.

IcantDo55

iTrader: (11)

Oh well short lived excitement. Problem came back last night after 5 miles of driving.

Any other ideas???

elderc

Do you have a scan tool that logs live streaming data ? If so you could see what going on when it throws the code.

If not pm me I have one you can use.

IcantDo55

iTrader: (11)

I do, just don't know what I'm to be looking for.




The only code I keep getting is P0304, others were one time. As many times as I clear P0304 it keeps coming back, and so does the engine miss.

Could be........

P0304

Ignition timing without specification

•Air gap of crankshaft position sensor without specification Set
•Ignition coil malfunctionReplaced
•Ignition control module malfunction
•High·tension lead malfunctionReplaced
•Spark plug malfunctionNEW
•Fuel injector malfunction
•Fuel pump malfunction
•Fuel filter clogged
•Fuel delivery hose clogged or leakingNo leaks
•Fuel return hose clogged
•Pressure regulator malfunction
•Pulsation damper malfunction
•Purge solenoid valve malfunction
•Positive crankcase ventilation valve malfunction Huh? how would that help?
•Leakage in intake-air system No leaks
•Insufficient compressionChecked, ok
•EGR system malfunction
•Vibration of drive unit don't feel any
•Excessive load of A/C compressor,power steering oil pump ,and generator
•Mass airflow sensor malfunction POSSIBLE
•Engine coolant temperature sensor malfunction CAUSE
•Intake air temperature sensor malfunction
•Crank shaft position sensor malfunction
•Camshaft position sensor malfunction
•Throttle position sensor malfunction
•Heated oxygen sensor(front)malfunction
•Vehicle speed sensor malfunctionJust replaced
•Break switch malfunctionWTF?
•Open or short circuit in wiring harness
•Poor connection of connectorCleaned a sensor plugs
•Vacuum hoses damaged or loose Looked, found none

Stephanie Turner

Because you are inadvertently changing the amount of air or fuel delivered. Either too much fuel or too little fuel in one cylinder. Or think it of this way - what can affect one cylinder and not the others? Rod, piston, coil, spark plug, plug wires, or injector. The rod damage, usually bent if not thru the block, will make a loud noise. The piston will leak oil out the tailpipe or cam cover breather. The only other non obvious cause would be the injector, coil, wires, or spark plug. I have seen bad injectors cause misfires several times, even on my car. It is easy enough and fairly inexpensive to fix.
Stephanie

IcantDo55

iTrader: (11)

Well Steph, you were right. Pulled the intake today to swap around the injectors and see if the problem followed the #4 injector and found this:



Attached to this:



I'm thinking I might have found my Cyl #4 misfire P0304, what you think?

I remember seeing a TSB or a Recall on the 1999-2000 about the EGR tube causing these issues, what was there fix and does anyone got a injector and a wiring harness from a 1999-2000 I can have cheep, It seems to go from the front of the motor there is two plugs and back to the coil packs and the fuel injectors, let me know.