OBD II P0301, please help me.. details inside

[Henry.E]

Hi,

I recently got the P0301 Cylinder #1 missfire code after doing the following work in my Mazda Protege 2002 with FS engine automatic trans, Ill be as detailed as possible:

- Took it to a mechanic to replace the oil pump since I was getting low oil pressure and having the oil light flicker at idle sometimes.
- In order to do that he had to take out the timing belt, alternator belt and also the valve cover and gasket among other things.
- He was able to change the oil pump, and put everything back in place and the oil pressure is now good. However, a day after I got the P0301 code.

This is what Ive done so far:

- Replaced all spark plugs with NGK BKR5ES 11
- Moved the coilpacks and checked there's good contact with the spark plugs. The code is always P0301.
- Verified that there's no vacuum leaks.

I do have some questions I hope someone can shed some light in order to fix this:

I notice that after the work done on the car, the idle RPMs are now lower, before they were 800 - 900 at idle, now theyre about 700 - 750. I noticed that the mechanic had a hard time setting the timing belt correctly, could this be the reason the RPMs are lower now? and the missfire is due to a bad timing belt setting?

Any other ideas?

Ive never had this code before the oil pump change, so Im thinking that the problem is related to something during the oil pump change procedure or timing belt settings, also possibly the valve cover and gasket. Ill really appreciate any help!

 

[Henry.E]

any ideas?

 

[hornsfan10609]

If the timing belt is not installed properly the car may misfire. It is typically caused by the ignition setup but since you replaced it and the timing belt was just removed I would guess it's the belt. Could also be caused by a bad ignition coil as they fail fairly often on these cars.

 

[Henry.E]

If the timing belt is not installed properly the car may misfire. It is typically caused by the ignition setup but since you replaced it and the timing belt was just removed I would guess it's the belt. Could also be caused by a bad ignition coil as they fail fairly often on these cars.

Could a timing belt not installed properly cause lower RPMs at idle? I'm trying to check why are idle RPMs lower after the work done on the car

 

[hornsfan10609]

Yes it could, but so could the misfire

 

[Henry.E]

Yes it could, but so could the misfire

Thank you for your help. I'll get the mechanic to re check the timing tomorrow.

I wanted to let you know about something, cause I would really like to avoid buying new coils or plug wires unless they're really bad.
I've noticed that the RPM's are fluctuating just a bit at idle, for example, idle rpms are 750, the needle will go to 900 and then down, and it's not a lot I know I just wanted to confirm if the ignition timing could create that kind of behavior..

 

[Henry.E]

I checked the timing belt and the timing marks were definitely not right, so I took it off and made sure all the marks aligned, so far it's been two days and no more P0301, before this it was shooting the code every time I drove it so I think it's all good and the car runs better now. I'll leave this here in case anyone has the same issue.

Thanks a lot!