Need some help troubleshooting a 2013 Mazda CX-5 2.0L w/130k miles
Original problem: DTC P0304 – Cylinder 4 Misfire and sometimes a P0300
Symptoms:Misfires / hesitation under load only. Idles and rev's freely in park fine. Higher RPM driving seems OK too. Lower RPM with high load, bad.
Things tried:
1. Replaced all 4 spark plugs (BOSCH 9683 OE Fine Wire Double Iridium)
2. Swapped coil #4 with coil #3
3. Inspected intake pipe after MAF for leaks.
4. Cleaned MAF with MAF cleaner spray. Didn’t look bad and Torque app reports reasonable MAF readings.
5. Inspected PCV hose for leaks
6. Tried spraying carb cleaner around intake manifold seals and various other potential leak areas. No change in RPM.
7. Took to Mazda dealer for diagnosis. Mazda recommends replacing all 4 coils based on a TSB and current DTC P0304.
8. Purchased 4 new coils from RockAuto and installed myself (easy to do, 5-minute job, no reason to pay anyone).
9. Tried disconnecting each coil at idle. Engine sounds equally rough with any one cylinder disconnected. On all 4 coils it sounds quite smooth/normal. Engine is smooth in park all the way up to 4000 RPM (where I stopped). Seems to start bucking (misfiring) under load only.
10. Filled 3/4 of tank with 93 octane and some Techron fuel cleaner.
No dice. Still getting P0304
I found TSB that Mazda Tech was referencing about the coils:
https://static.nhtsa.gov/odi/tsbs/2016/SB-10085446-6903.pdf
I’m a little annoyed that it described the exact troubleshooting procedure I did by swapping coils, yet tech said TSB said to replace all 4 coils.
At this point I lost all faith in going to dealer to diagnose issue. We’ve paid $127.78 in diagnostics and replaced 4 coils needlessly.
I started a deeper dive in my own troubleshooting. Didn’t want to do this earlier in the week because I just got LASIK and I couldn’t see well.
I connected the CX-5 to my HP Tuners Scanner and pulled what PIDs I could with it.
First thing I noticed was the LTFT (Long Term Fuel Trims) we basically getting maxed out ADDING FUEL, while the rear O2 sensor (B1S2) was at a near constant .800v or higher (RICH!!!)
My first scan didn’t have data for the front O2. I learned later that it’s not a narrowband in this car but a 5-wire wideband O2 sensor for B1S1. I eventually found the PID to give me lambda, but not before I replaced the front O2 sensor with a new DENSO 2345059 {#PE01188G1A}.
So with a new front O2 sensor, I went for another drive. I noticed under load (greater than 75kPa MAP) is when the engine misfires. As I mentioned before, in park you can rev the motor freely to 4000 RPM without it getting rough.
My scan shows the WB O2 ratio to be withing 1% of the Commanded EQ, yet the rear O2 is pretty consistent staying above .750v (rich) unless I do a deep decel and then it will read .100v. Never really is any middle ground with the rear O2
I think I verified that the High Pressure Fuel pump is working to spec. 435 psi at idle and ~2100 when engine load is above 60% and above 3000 RPMs. Using this procedure here and this one here.
Still getting the #4 misfire, I decide to replace the #4 injector. While I have the intake manifold off, I notice quite of bit of carbon/oil build up on the intake valves. I cleaned those up with carb cleaner 2 valves at a time (valves closed). They cleaned up reasonably well.
No more P0304 but now getting a P0171 (Lean Bank 1) and still has same symptoms.
Still observing:
-Normal WB (front) O2 operation. I never see lean accept on deep deceleration.
-Rich rear O2's
-Short Term and Long Term Fuel Trims adding a lot of fuel, especially at higher loads when car hesitates / misfires.
I've since tried:
-Swap the MAF with a known good one
-Unplugged battery for the entire night
-Cleaned MAP sensor
-Performed a compression test: 160, 160, 170, 160 PSI respectively.
-Performed a leak down test: All cylinders gave no significant loss.
So what is your opinion? I don't understand the logic of this car. Why a lean code, when the commanded EQ is close? Why is the rear O2 reading rich?
I have a HP Tuners scan if anyone has it and wants to take a look.
Appreciate any help. I'm stuck. Trying to help out a family member with their CX-5.
-Andy
Original problem: DTC P0304 – Cylinder 4 Misfire and sometimes a P0300
Symptoms:Misfires / hesitation under load only. Idles and rev's freely in park fine. Higher RPM driving seems OK too. Lower RPM with high load, bad.
Things tried:
1. Replaced all 4 spark plugs (BOSCH 9683 OE Fine Wire Double Iridium)
2. Swapped coil #4 with coil #3
3. Inspected intake pipe after MAF for leaks.
4. Cleaned MAF with MAF cleaner spray. Didn’t look bad and Torque app reports reasonable MAF readings.
5. Inspected PCV hose for leaks
6. Tried spraying carb cleaner around intake manifold seals and various other potential leak areas. No change in RPM.
7. Took to Mazda dealer for diagnosis. Mazda recommends replacing all 4 coils based on a TSB and current DTC P0304.
8. Purchased 4 new coils from RockAuto and installed myself (easy to do, 5-minute job, no reason to pay anyone).
9. Tried disconnecting each coil at idle. Engine sounds equally rough with any one cylinder disconnected. On all 4 coils it sounds quite smooth/normal. Engine is smooth in park all the way up to 4000 RPM (where I stopped). Seems to start bucking (misfiring) under load only.
10. Filled 3/4 of tank with 93 octane and some Techron fuel cleaner.
No dice. Still getting P0304
I found TSB that Mazda Tech was referencing about the coils:
https://static.nhtsa.gov/odi/tsbs/2016/SB-10085446-6903.pdf
I’m a little annoyed that it described the exact troubleshooting procedure I did by swapping coils, yet tech said TSB said to replace all 4 coils.
At this point I lost all faith in going to dealer to diagnose issue. We’ve paid $127.78 in diagnostics and replaced 4 coils needlessly.
I started a deeper dive in my own troubleshooting. Didn’t want to do this earlier in the week because I just got LASIK and I couldn’t see well.
I connected the CX-5 to my HP Tuners Scanner and pulled what PIDs I could with it.
First thing I noticed was the LTFT (Long Term Fuel Trims) we basically getting maxed out ADDING FUEL, while the rear O2 sensor (B1S2) was at a near constant .800v or higher (RICH!!!)
My first scan didn’t have data for the front O2. I learned later that it’s not a narrowband in this car but a 5-wire wideband O2 sensor for B1S1. I eventually found the PID to give me lambda, but not before I replaced the front O2 sensor with a new DENSO 2345059 {#PE01188G1A}.
So with a new front O2 sensor, I went for another drive. I noticed under load (greater than 75kPa MAP) is when the engine misfires. As I mentioned before, in park you can rev the motor freely to 4000 RPM without it getting rough.
My scan shows the WB O2 ratio to be withing 1% of the Commanded EQ, yet the rear O2 is pretty consistent staying above .750v (rich) unless I do a deep decel and then it will read .100v. Never really is any middle ground with the rear O2
I think I verified that the High Pressure Fuel pump is working to spec. 435 psi at idle and ~2100 when engine load is above 60% and above 3000 RPMs. Using this procedure here and this one here.
Still getting the #4 misfire, I decide to replace the #4 injector. While I have the intake manifold off, I notice quite of bit of carbon/oil build up on the intake valves. I cleaned those up with carb cleaner 2 valves at a time (valves closed). They cleaned up reasonably well.
No more P0304 but now getting a P0171 (Lean Bank 1) and still has same symptoms.
Still observing:
-Normal WB (front) O2 operation. I never see lean accept on deep deceleration.
-Rich rear O2's
-Short Term and Long Term Fuel Trims adding a lot of fuel, especially at higher loads when car hesitates / misfires.
I've since tried:
-Swap the MAF with a known good one
-Unplugged battery for the entire night
-Cleaned MAP sensor
-Performed a compression test: 160, 160, 170, 160 PSI respectively.
-Performed a leak down test: All cylinders gave no significant loss.
So what is your opinion? I don't understand the logic of this car. Why a lean code, when the commanded EQ is close? Why is the rear O2 reading rich?
I have a HP Tuners scan if anyone has it and wants to take a look.
Appreciate any help. I'm stuck. Trying to help out a family member with their CX-5.
-Andy
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