misfiring problems. need help asap

[lowtege]

So a few months ago my car stalled on me at a stoplight. I started it back up and immediately started misfiring on me. Ran diagnostics and found out I had a misfiring in cylinder 4. So I changed the spark plugs and spark plug wires and found that only cylinder 4 spark plug gap was completely closed. Yes I used NGK. For about a month after, it ran fine and CEL went off. Then it started misfiring again. Same cylinder. So I changed both coil packs. CEL went off, car ran fine. 2 weeks later CEL came back on, car started misfiring again. Same code: Misfiring in cylinder 4. Come to find out there was some wires from the coil packs chaffing up against my valve cover and shorting it out. CEL went off again and car ran fine. about a week after THAT, CEL came back on and I checked the 4th cylinder plug. Gap was completely closed again. almost like something was stuck in my head and the piston was coming up and smashing it against the spark plug electrode. I triple checked the sizes of the spark plugs and they were the right size. Got a hold of a camera to look inside my 4th cylinder and there was no sign of damage to the walls or the head of the piston. I had it compression tested and it was roughly 175 lbs. (ideal). I asked a mechanic and he said it was possible that my cat was bad and my exhaust manifold was getting too much back pressure, and sucking ceramic pieces of the cat up into the head causing the piston to smack it against the spark plug and spit them back out. Which made sense cause the last time it was misfiring i heard tinging in my motor like rocks hitting metal. but i took out the cat today, and it seemed fine and perfectly intact. And this time the spark plug gap isn't closed. I'm just looking to see if anybody has any sort of ideas it could be. Let me know!

 

[mrwicked]

Change your cat out I had something similar to this ... Ended up getting a header no more probs ..

 

[lowtege]

I was thinking the same thing. will the header throw me a CEL tho because no O2 sensor?

 

[mrwicked]

It will but there's a non fouler setup you can run and CEL will be gone unless you actually have a bad coil or spark plug

 

[Broffybakes]

Need help urgent ? I have a 1999 mazda familia with the zl-ve engine, its was automatic and i change it to manual (problems):i am missing my airflow box the part that the filter goes on the bottom half (it was stolen) it had a burnt knock sensor ,blown head gasket around the compression rights,and the gas needle moves every move i make depends on the turn are what ever i have a problems on hill (not my driving skills)when the gas is low are on the first mark,and it has a flat spot on move off if i push in the clutch and rev it will take of then die down immediately then pick back up again. Can anybody shine any light on this matter are know how i should ask?

 

[zizaspeed]

did you end up figuring out what your problem actually was?

 

[T-Rash]

Ive had the same problem in cylinder #4 as well. Basically signed up on the forum to research this. I have 03 P5 manual trans with 160K. Stock engine. The spark plug tip has been crushed 3 times now, mostly under higher rmps driving conditions. The first time seemed like a random misfire, regapped the spark plug, quick fix. 2nd time, same thing. 3rd time I had just replaced all spark plugs, wires and coils, and crushed the spark plug the day after. The shop I take my car to mentioned maybe some carbon build up broke loose and hit the tip, but no way could that happen 3 times in the same cylinder. They didnt mention the cat/ header problem from above. I would like to find the cause of this as Im wondering if it could lead to complete engine failure. As of now, I carry extra spark plugs and a wrench just in case... Other than this the car runs and drives great!

 

[zizaspeed]

You might want to call mazda and see if your car falls within the recall vin number boundaries. Recall regarding the VTCS or VICS breaking and going into motor, cant remember which one.

 

[T-Rash]

no luck on the recall. taking her in Thursday to check and see if VICS valves are missing any screws. Prob try and replace or lock tite the loose screws and go from there... Thanks...

 

[Installshield 2]

did you try switching the injectors? Closed plug gap doesn't always mean contact was made...extremely lean AFRs can often flash melt a plug head, then the compression cycle itself will close it (as its nearly liquid for a few miliseconds)...is it very obvious that something actually hit it? Are other parts of the plug destroyed? Does it still work if you re-gap the plug?...sound isn't a give away either, as a lean mixture will make all kinds of noise too and the piston literally flips out from having improper pressure gradients inflicted it on it (i.e. ping)

I mean...only a few things can happen with something literally lose in your combustion chambers...A) it just happens to hit the plug at just the right angle to flatten it multiple times (I'd assume that is not likely), while managing not to hurt anything else in the process. B) it will get blown out of the chamber almost immediately and you'll never know it (possible, but lucky) and C)...it will wedge itself between the piston crown and cylinder wall...and give you a very bad day (most likely thing to happen imo)...

I do agree this is a weird one though. Just seems odd to me that if this is happening over a few month period, that is a lot of time for something to be rattling around in there...not hurting anything but an occasional spark plug...even in a low compression engine like the FS, internal combustion is one hell of a violent affair. If its just some debris or a screw in there, i'd imagine it would be light enough to get pushed (then sucked) right out into the exhaust system on the very first cycle it ended up inside...either that, or what i already mentioned, wedging into the cylinder wall and seizing the engine. let alone if it decided to wedge into the valve seat, in which the next cam cycle would either crack the cam lobe, bend the valve stem...or both...or the opposite haha, a valve would remain stuck open (little something keeping it from fully closing) and you'd be burning all kinds of oil and the engine would sound radically off...anyway, all of these you'd immediately know something was up...

i'm leaning more towards some form of detonation. A faulty injector is the first thing to check for when you have specific cylinder mixture issues, as fuel pump/emission system problems will create the P0300 code...which specifies multiple cylinder misses...One way to check it is to swap the injectors...there are 2 blue and 2 green iirc, swap #4 to the other cylinder with the same color injector and see if that plug flattening follows it...if not, hell it just might be something in there...and if this is all it ever did, great news for you haha.

 

[T-Rash]

Upon removing the intake, 3 of the 4 VICS butterfly valves fell out, with no screws to be found. The 4th one had very loose screws holing it in place. I ended up removing the valves and reinstalling the same intake manifold. I lost a bit of power on the low end but really feel some increase power on higher rpms. Also feel like I lost a bit of miles per gallon. I really cant believe how lucky I was that all that happened was a couple of crushed plugs. I know how bad this could have turned out. Thanks all for the input. I feel alot better knowing there isnt any loose screws, except in my noggin...

 

[Installshield 2]

wow...yeah that is crazy...are you sure it was the VICS system? The VICS butterflies are farther back inside the manifold, the VTCS butterflies are right there at the head...

either way, glad you found it...and definitely got away lucky...

are you sure the screws are out of the cylinders though? They could still be in there...were the butterflies just laying in the runners still haha?

 

[T-Rash]

We removed both sets.