This is a tuff one to put in writing. I have a 2006 Mazda 6 4 cyl that has 107000 miles on it. Two day ago I noticed that during acceleration it was missing in a very perfect rhythm (not your normal sporadic missing). It is a longer missing with a slight roaring sound. I pulled a spark plug wire and the miss was noticeable during idle. No codes have been shown, mechanic has put on his machine with no luck. He feels is a cam/timing issues. Any suggestions on process of elimination?

 

Misfires are a pain in the a.s.s especially when no code or cel light flashing?!

Missfires Can Be Caused By a Million and One Things,

Vac Leaks
Wiring Issues
Spark Plugs(Even Fresh Spark Plugs That Are Crappy Quality.... E3 And Such)
Ignition Coils
Alternators (Search EMI)
MAFS
Injectors
Injector O-Rings
Intake Gaskets
TB Gaskets
PCV Hoses
PCV’s
Malfunctioning EGR
Malfunctioning CAS
O2 Sensors
Aftermarket Intakes
Intake Hoses
Vac Lines
Timing Chains
Timing Chain Tensioner
Broken Cam Gears
Malfunctioning Cam Sensors
Incorrect Crank Gears(The I4 Has Like 40 Different Configurations For Whatever Reason)
Incorrect PCM Flash
Issues Within The PCM
PCM Wiring
Bad Diaphram Within The FPR
Issues Within The Fuel Pump
Dirty Fuel Filter
Dirty Fuel Lines
Pre-Cats/Poor Exhaust Flow

If the above gaskets/seals have not been changed, change them. Clean your MAF sensor, throttle body.
Change your PCV valve and probably that short hose as well.
Inspect the intake accordian tube for cracks. Inspect for vaccuum leaks.
Put in a good Fuel system cleaner: ClickMe
Inspect wires. Re-set ECU after doing above.

 

Thanks for the list. The confusing part for me is the miss has such a perfect pattern and is smooth. Its crazy! If it was a spark plug or injector, my guess would be that the miss would be sporadic and rough. Would a mazda dealer have the testing equipment to pinpoint with no problems. My mechanic is solid, but he admitted he was a little limited with testing.

 

NO, farting around and testing and a pain in the a.s.s is in your future!

 

are you sure its a missfire? If you have an automatic transmission that could be a torque converter going in and out of lock-up, which is not normal by the way.

 

I know going to a Mazda dealer isn't cheap, but with the genuine tester you can enter a section that shows a log of each & every misfire on each individual cylinder. Even if there is no codes you can see misfire counts.

 

The mechanic cleaned the throttle body and the misfire seem less noticeable but was still there. He hooked to his computer and found some very old codes, but did tell me the dealer could see things that he couldn't. Taking it Monday.

 

I guess all computers aren't alike!

 

Late update, but it was the front O2 sensor that was causing the miss with no codes. Mazda dealer did not get any codes, but emailed Mazda for support which sent some TBS information. Unplugged sensor car ran great. Sensor- $200 Service/labor/ Diag $140.

 

I know it's an old thread but in case anyone else comes searching for answers... My miss started, was a little better w/ premium but eventually got worse until CEL popped on. Read this forum and decided to try plugs, coils, and MAF. Didn't cheap out on the parts but didn't go crazy either. A couple of hours of work, cranked it up and all good. No CEL, no missing. Car runs great. Had it been O2 sensors, vacuum leaks, etc. at least I would have been a step closer. Now to tackle the common oil leaks!