Code P0301. Cylinder 1 Misfire. Running Lean also...Cause?
 

Hey Everyone,

Recently my 1996 Mazda Miata has been throwing a P0301 code and Running super bad. It seems like cylinder 1 is not there at all. The car tends to only act up late night or early morning when its cold outside, maybe just a coincidence?

It will stutter and stumble at first start up, and after a minute or two it will throw a flashing CEL that when pulled is a P0301. Twice now I have turned the car off after the code has been thrown, and it was running bad... And I let it sit for 15 minutes. Tried to start it again, and it started right up like nothing was wrong. I dont know if this is dealing with engine tempratures or? When the car is acting up it makes itself very clear, it runs on 3 cylinders and sounds like a subaru. Its very tempramental. My Air/Fuel ratio's when the car is running bad are near the high side of things and sometimes maxing out the gauge. Its running very lean.

My question is could an injector cause this, or maybe an issue with the AFPR? Please let me know. Thanks.

your afpr is ok,check sompression on cyl 1,check your injector on cyl 1,check crank sensor for air gap incorrect,spark plug if foulting,check egr,fuel pressure & battery.your problem is cylinder 1 is irregular on input from crank sensor,good luck.

start with your batttery make sure it hold good charge still,start changing your spark plug mine as well,chaeck your crank sensor Disconnect the crankshaft position sensor connector. Measure the resistance between terminals A and B by using an ohmmeter.
Specification: 500 - 600 ohms @ 20°C (68°F) ,If not as specified, replace the crankshaft position sensor.and so on other list.

P0301 codes are either a dirty crank sensor (front of engine) or timing belt needs replacing. Some people say they get away with changing the plugs and wires cause sometimes they have fault wiring.

Best thing to do is switch the plugs around and see if the code moves to another cylinder. Then swap injectors around and see if it moves to another cylinder.

But I would suggest doing a timing belt job. Engine cold- belt tighter so you wont see the stumble. Engine warm - belt's warmed up and you see stumble.

He said it was the opposite though.

Hey op are you on band aids or using an ems?

+1 on the compression check and checking spark plugs and injectors, i dont think its the timming belt as that would throw a p0300 random multiple missfire not just one cylinder the same one cylinder at that.

Kris.

The car is tuned on AEM FIC, its a piggyback ecu.

I pulled the plug for cylinder 1 and it looked ok. I am hoping that it is a sensor issue of some sort. I am a bit nervous to check compression, knowing my luck I would need a new motor.


Things I will check today include...
1. OHM check the 305cc Green top supra injectors. I think they should OHm in around 14.7?
2. Check crank position sensor. OHM around 500 - 600
3. Might go buy a new set of wires. The plugs are pretty new.

I just find it odd that sometimes the car will crap out for a few minutes, then I let it sit for a bit and restart it and its good to go. My thottle response has been a bit odd lately too, not sure if its the same issue. But when I am lightly getting back on the gas (from a stop, or shifting) the car had a hesitation and stumble, it was also giving lean radings then too. I was going to look into a new TPS but after yesterday I think I have bigger issues to deal with.