Mazda Ted

So before I had an issue where the car would get a flashing cel if I went past 7k rpm, the code read P0300 Random misfire cat damage.

So recently I replaced the spark plugs with ngk ones and I put on a new set of coils and wires. Now the problem isn't as bad it will rev to about 7.5 - 8k before I get the flashing cel.

The car has a cold air intake a racing beat catless midpipe and an hks exhaust. (I doubt these would cause the issue but I put it just incase.)

The car has about 129,500 miles on it, I bought it around 120k and im pretty sure it has the original motor, incase maybe this is a compression issue.

Just wondering if you guys had any ideas on how I can unlock that extra 1k rpm range, or if maybe I need a rebuild?

Loki

iTrader: (1)

Do you have oil in your intake accordeon and/or filter?

Ricky SE3P

iTrader: (10)

Where in CA are you? What cold air intake is it?

Mazda Ted

I used the have that problem with the stock airbox so I changed the oil and made sure it wasn't overfilled and cleaned out the intake, but then I put a Cold Air Intake on anyway.

But no I haven't had the issue since I changed the oil.

Mazda Ted

@Ricky SE3P
Its just the cheap Ebay cold air intake pipes. but I put on a Spectre Filter.
I live in Santa Barbara County.

Loki

iTrader: (1)

Oh boy. Yeah, you're going to want that off the car. The stock intake is already a cold air and very good. Stuff you get off ebay is a downgrade and causes problems like this. You could have other problems too, but the intake isn't helping. Stock, AEM/MazdaSpeed or Racing Beat. Nothing else.

Loki

iTrader: (1)

If you're referring to the oil in the intake problem, overfilling would definitely do it, but one scenario is at high rpm blowby forces oil into the intake where it gets ingested and causes stumbling and smoke from the exhaust, as well as fouls the MAF sensor if it gets on it. Usually it leaks down to the filter and then is carried by air from the filter onto the MAF.

Mazda Ted

So I replaced the MAF sensor when I did the intake and I did notice that there was a little bit of oil in it and I did get a much smoother and faster power delivery, but what is bothering me was that it misfires at just before 8k. I would also like to add that this is only under load, when I'm in neutral it revs freely. Would the oil that's shooting into the intake cause the misfire? And if it is do you think a catch can could solve the problem.

Just a note I still had this same problem before I installed the intake. Also what are the other features in the AEM cold air intakes because they have the same fitting and size, the only difference I can see is the filter and the paint. I just wanna know what the night and day difference is gonna be before I spend 400 bucks on something that looks and fits the same?

Ricky SE3P

iTrader: (10)

Santa Barbara is a bit far for me, 2.5 hours, theres a good chance you might find someone with a -rotary specific- compression tester within 1 hour of you who could do a test on your motor.

Oil getting on the MAF would definitely pose a problem. Installing a quality oil catch can in the intake would make a notable difference in avoiding air in the intake. Those aftermarket intakes will cause major issues with proper airflow measurements. You need a intake like Loki mentioned, and making sure the mesh screens in the intake are properly installed and secured to help even out the flow of air so the airflow sensor could get a good, reliable measurement.

Which spark plugs from NGK? Where did you order them from? How many of each did you get? And did you install them in the correct locations?

What spark plugs wires and coils? Where did you order them from? Are they installed in the correct locations?

Meat Head

Also, what replacement coils did you source? Saving money on these doesn’t work out well. Is it a misfire around 8,000 or is it just the slight stumble that can happen around 7500 when the APV actuates?

Mazda Ted

It actually does feel like a slight stumble at around 7500 and then if I push it to 8k I get the misfire.

Also the spark plugs are the NGK Laser iridium ones and I bought 2 leading 2 trailing and yes I installed them correctly, this would be my third time doing spark plugs. Before I was running LS Coils and wires but I decided to downgrade I guess to see if they were the problem, and I bought AutoZone coils and wires. And it did improve a little because before I could only make it to 7k before the misfire.

Mazda Ted

I will see if putting on the stock intake will help & look into getting a catch can.

I bought the spark plugs, coils, & wires from AutoZone. I got 4 coils 1 set of wires and 4 spark plugs 2 leading 2 trailing, Im positive I installed them correctly. (This is the 3rd time I have changed this cars spark plugs.) I did each spark plug individually, I measured the old wires and new ones to place them in the right spot and I think the coils are all identical so I'm not sure that matters. I installed all the connectors in the right spot I snapped all the wires into the coils nice and tight. Like I said the car runs great it idles amazing, the only problem is it wont rev high in gear without the misfire/flashing cel. I can get it to go above that to its full potential but it feels like I am harming the car because it bogs out and then a second later it goes higher so I don't like to do that. But when its in neutral the car will rev freely no misfire.

I will see if I can find a compression tester but I might buy my own because I feel like it would be a useful tool since I plan on rebuilding this engine once its done, and maybe putting on a turbocharger once the motor is healthy.