CX-5 Misfire

[50jeffrey]

2015 2.5L

Under moderate or more throttle at speeds above 40, the car stumbles. Once throttle is backed off to stay at a given speed, everything is fine. There are absolutely no codes set.

Plugs were replaced about a year ago with NGK Ruthenium and all 4 coils were replaced at the same time (with Hitachi). Long story about the plugs and coils. Turned out to be carbon buildup on the intake valves. Codes were set back then.

Any suggestions?

Thanks in advance.

 

[edmaz]

What diagnosis have you done so far?

 

[50jeffrey]

What diagnosis have you done so far?

Only scanned for all codes. Hard to trouble shoot without a code as a starting place.

 

[AVC]

If you have access to a basic scan tool, you should be able to watch catalyst and emissions misfire counters. And try to get it to misfire by driving steady at 20 mph or so, put the trans in manual and shift it to 5 or 6 and slowly press the throttle. Misfires are most likely to occur at low RPM high load.

 

[50jeffrey]

I won't have access to the car again for at least another week.

I'll post more when I have more information to share.

 

[CX-5um]

2015 2.5L

Under moderate or more throttle at speeds above 40, the car stumbles. Once throttle is backed off to stay at a given speed, everything is fine. There are absolutely no codes set.

Plugs were replaced about a year ago with NGK Ruthenium and all 4 coils were replaced at the same time (with Hitachi). Long story about the plugs and coils. Turned out to be carbon buildup on the intake valves. Codes were set back then.

Any suggestions?

Thanks in advance.

What mileage? Why were all 4 coils replaced? What is your normal driving distance?

A cheap scan tool you can purchase will save time from guesswork.

 

[MyFirstMazda]

My guess is the spark plugs need to be replaced, that they are not OEM spec.

 

[50jeffrey]

Car has 111k. Plugs and coils changed due to parts cannon being thrown at it last summer based on P0300 code coming on intermittently. Finally a can of CRC Intake Vakve cleaner was used and the code went away.

But now, no matter how much stumbling you cause to occur, no codes.

 

[Odrapnew]

My wife's old 09 CX9 had a fairly severe misfire at highway speeds under load.
The car bucked quite a bit. Never threw a code, so I thought it was a transmission issue, but after some additional testing I started leaning towards misfire.

I bought a cheap OBD2 Bluetooth reader (~$20) and the Torque app (full one for $5).

I installed it and had Torque running while I drove around and forced it to stumble and watched the misfire counts go up on a couple cylinders.

Luckily they were on the front of the engine, so I replaced the front 3 spark plugs and the issue went away.

I'd look into a OBD2 adapter and app if I were you if you're up to the task of self diagnosis.

 

[CX-5um]

Car has 111k. Plugs and coils changed due to parts cannon being thrown at it last summer based on P0300 code coming on intermittently. Finally a can of CRC Intake Vakve cleaner was used and the code went away.

But now, no matter how much stumbling you cause to occur, no codes.

Issue Resolved?

 

[ruthrj]

I’d try new spark plugs that are either OEM or the NGK plugs that are likely the OEM ones. Same number on them, but the NGK don’t have the Mazda logo. If that doesn’t work, I’m thinking the intake valves need a more thorough cleaning than what a can of CRC alone can provide.

 

[AVC]

Unless the plugs are obviously fouled, really worn or damaged, that's not the issue. You really do need to start with basic scan data graphs at idle, cruising and when it stumbles/sags; fuel trims, MAF, MAP, misfire counters. Without that, everyone here is spit-balling and it'll just cost you money to keep reloading the parts canon.

 

[Jmaz]

I’d try new spark plugs that are either OEM or the NGK plugs that are likely the OEM ones. Same number on them, but the NGK don’t have the Mazda logo. If that doesn’t work, I’m thinking the intake valves need a more thorough cleaning than what a can of CRC alone can provide.

What about a can of Berryman B-12 Chemtool ( or other strong) injector cleaner in the tank. What is the condition of the air filter. And for good measure, has the throttle body ever been cleaned even though I think it would have to be horribly dirty to cause this problem.

 

[ruthrj]

A can of B-12 in the gas tank couldn’t hurt, but something is telling me it may be intake valve related. Gas treatment could help the injectors but won’t help the valves. The only time my car has ever behaved as the OP described is after an intake valve cleaner treatment until the cleaner is gone (but it admittedly throws a code if you push it too hard).

 

[50jeffrey]

Chevron gas treatment was added about a month ago. and the battery was replaced last weekend. Oh, and that flashing check engine light and steady TPMS and ABS lights situation happened again tonight. Car dramatically lost power. Pulled the car over and re-started it and all of the warning lights went out and car returned to "normal". Except for the stumble.

 

[Tchman2016]

A flashing check engine light should not be taken lightly. It is a severe problem that the ECU detects as something that can damage the engine. That is why it puts the vehicle in limp mode. You WILL cause damage if you continue to drive and do not get the issue properly diagnosed and fixed. It is not the same as a steady illuminated check engine light. That kind of problem needs a real scan tool with real live streaming and freeze frame data, history, pending and active codes and pids of all systems to diagnose

 

[50jeffrey]

I have an appointment at a dealer on Wednesday. The perplexing thing is that as soon as you restart the car. all but the miss seems to clear up.

 

[Tchman2016]

I have an appointment at a dealer on Wednesday. The perplexing thing is that as soon as you restart the car. all but the miss seems to clear up.

I wouldn't bother with a dealer, they are way too high for non warranty work since you have none. Do a Google search for a highly reputable independent local mechanic if you can. The dealer will eat you for breakfast.

 

[50jeffrey]

Perhaps I will try that route.

 

[Tchman2016]

This sounds like a fuel delivery problem, if not two problems. Classic sign of a clogged fuel filter is what you describe at medium and above throttle load. You will need to have the fuel pressure at the rail checked for proper psi as specd. If pressure is low, change the filter and test again. If still low then fuel pump is failing.