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View Full Version : Checking my thought process on this. '08 Mazda 3.



MCcelica
12-17-2012, 09:04 AM
I was on the way home from my folks place with my wife, and was driving her car, the 08 Mazda 3 mentioned in the subject line.

At the beginning of the trip we both noticed a bucking to the car. It was when I had the cruise control engaged. The car would buck to speed up, then slow down drastically until I turned the entire cruise control off. Figured it was a CC issue until about 20 minutes later.

That's when it intermittently started bucking, but it would only buck when under load. During the rest of the hour trip, that intermittent nature gradually became every time the engine was under load. Now, it's not a particularly violent bucking, but it's enough for both of us to notice. So its more of a surge, then withdraw on the power with consistent pedal pressure.

It is NOT throwing a CEL, and upon return I yanked all the plastic crap off and started giving vacuum hoses a visual inspection which yielded nothing. I haven't poured water on them yet as we just got back, and she has to work tomorrow (I'll probably drive her in my car). I don't expect to find much vacuum hose wise as they all look and feel to be in good shape.

Out of curiosity, I checked the spark plugs. They are all white which tells me she's running lean.

Generally she runs the low grade gas (85 Oct), which could be gunking up fuel filters and/or injectors. I'm leaning towards filter since all cylinders were equally white. It could also be a pump that's on the outro as well.

So tomorrow I'm going to drop 'er off at work, pick up some fuel system cleaner (any recommendations?), some new spark plugs, drive it around to let the fuel system cleaner work its magic, then get some higher octane gas and see if that gets any crap out of there.

I'm thinking it could also be a TPS, but I'm betting it's not that for three reasons. Usually cheap stuff goes first being one, it may throw a CEL being two, and I would think a TPS would cause other weird issues and not be limited to JUST when it's under load.

Let me know if I missed something, and fuel system cleaner recommendations would be great. Thanks.

Car_Barn_Bandit
12-17-2012, 09:12 AM
Mazda put out a service bulletin on a faulty fuel pump. Nice catch.

http://www.o-m-g-w-t-f.com/stuff/Mazdaspeed6/01-022-08-1919b%5B1%5D.pdf

(I try to check for service or recalls when I buy a new car, or a problem arises. It's been 50/50 for solving issues on other people's cars)

MCcelica
12-17-2012, 03:26 PM
She already had that replaced under the recall...

Course that doesn't mean it's good though. Just means I doubt they'd do it twice.

MCcelica
12-17-2012, 03:53 PM
Also that (plus further research) indicates the fuel pump recall is for the Speed3. She just has the 3. The only recalls out for her car are a power steering pump (the one I thought was replaced), a wiper motor, and a Thule roof rack.

Car_Barn_Bandit
12-17-2012, 04:53 PM
I had three water pumps in a row fail. You never know when you hit the misfortune lottery.

MrWOT
12-17-2012, 05:55 PM
Put some Redline SI-1 through it and change the fuel filter (before you drive it, don't drive it running lean like that). Could be be gunked up if it fills at cheap stations.

UtahSleeper
12-17-2012, 07:10 PM
I would do the fuel system cleaner or a full seafoam treatment and change the filter.

Maybe o2 also, but its wierd your not throwing a cell.

MCcelica
12-17-2012, 10:15 PM
Can't change the filter without doing the pump. That's 600 bones too. Let's hope it's not that.

UtahSleeper
12-18-2012, 01:01 AM
Really? Is it in tank? I thought most cars had a sock on the pump then an inline somewhere outside of the tank.

Luni
12-18-2012, 06:36 AM
You cant trust a spark plug reading if you were just crusing steady state. A 14.7:1 AFR or higher will read "lean" on a plug.

Im not saying thats NOT what your problem is, Im saying to take your spark plug reading with a grain of salt. Plugs read primarly the way they were last driven. If you were out beating the shit out of it before you last shut it off, then youd get some more color in those plugs. If you were just crusing at stoich for a few hours, those plugs wont have much on them at all. They WILL show lean because 14.7:1 IS lean in the way you read a plug.

I just put this out there just in case you guys werent totally aware of that.

However your symptoms indicate fuel issue. Whats odd is you arent pulling any sort of a misfire check engine light. How many miles are on the car? Which motor does it have?

MCcelica
12-18-2012, 09:19 AM
Finally tripped a CEL. The code was a bank 1 O2 sensor.

Putting the fuel system cleaner in definitely smoothed out the surging, but it never completely went away until I cleared the O2 sensor code. Changed out the plugs, and now she appears to be fully functional. I don't think that code would have cleared had I not put that fuel system cleaner in, though.

That pump is whack though. If you jack up the sock, you jack up the pump. It's all built together.

Btw, $300 for an O2 sensor is freakin whack too.

Didn't wind up needing either a pump or an O2 but still...

Fuck Mazda and their expensive ass shit.

Car_Barn_Bandit
12-18-2012, 09:34 AM
NGK?

MCcelica
12-18-2012, 11:42 PM
The O2 sensor is Bosch. Pump is OEM.

Car_Barn_Bandit
12-19-2012, 12:55 AM
The O2 sensor is Bosch. Pump is OEM.

I've had Bosch sensors that were garbage. OEM or NGK for jap motors.

Hipster Lawrence
12-19-2012, 04:24 AM
Your o2 sensor is $300 because it's an air fuel ratio sensor not an o2 sensor aka it's a wide band.

Most likely the ecu was running the fuel trims up trying to get a response from the sensor. When it was satisfied that the sensor wasn't responding is triped the code.

No real way of knowing without looking at the live data. The read a code and throw parts at it says are over.

There is no reason for the 85 octane to gunk up anything. I wouldn't go looking for a bad filter. They just don't clo anymore. That's why most cars have them
In the tank only now.

White plugs are normal these days. As Luni says a properly running modern engine's plugs will "read" lean by 1970s standards. I only "read" plugs when chasing coolant or oil burnin issues anymore. Unless they are just dripping with fuel, sooty or eroded I look elsewhere.

The Captain
12-19-2012, 10:46 PM
Zoom Zoom IDB!

MCcelica
12-20-2012, 07:24 AM
Your o2 sensor is $300 because it's an air fuel ratio sensor not an o2 sensor aka it's a wide band.

Most likely the ecu was running the fuel trims up trying to get a response from the sensor. When it was satisfied that the sensor wasn't responding is triped the code.

No real way of knowing without looking at the live data. The read a code and throw parts at it says are over.

There is no reason for the 85 octane to gunk up anything. I wouldn't go looking for a bad filter. They just don't clo anymore. That's why most cars have them
In the tank only now.

White plugs are normal these days. As Luni says a properly running modern engine's plugs will "read" lean by 1970s standards. I only "read" plugs when chasing coolant or oil burnin issues anymore. Unless they are just dripping with fuel, sooty or eroded I look elsewhere.

After I ran the fuel system cleaner through it, it got to where it only dropped power at 2800 rpm and picked right back up at 3000. At which point I figured the ECU had a bad fuel map. That's when it tripped the code. Once it got cleared and had to rebuild the fuel map from 0's it was fine.

underscore
12-20-2012, 08:05 PM
Btw, $300 for an O2 sensor is freakin whack too.

Holy crap, I bought a wideband sensor (brand new Bosch one) in the states for $50 for my wideband gauge, the cheapest I found for a 3 was $200 for the upstream. I shudder to think what that would list for in Canada.