08 Mazda 3 GT Hestitates and Stumbles

[Throttlemonkey]

First post here so I will start with the basic info:

Bought the car about a month ago as a replacement/upgrade to my old civic commuter car, read great online reviews about it everywhere. It had 42K miles and was in spotless shape, meticulously maintained and got a great price on a private party sale. Test drive was great but when i drove it home on the highway i started to feel a slight hesitation on hills. It also had a bent wheel that I couldn't feel until 60 mph but I had that straghtened and the vibration went away.

So, I started pouring through forums and found this to be common, unfortunately everyone thinks the issue is something different and has a different solution! I put in new plugs, K&N filter, cleaned the TB and MAF, grounded the TB, took it to the dealer to check motor mounts and that I hade the latest software and no engine faults. Not a lot of soot on the tailpipe as some have reported and 30 mpg avg. Everything is fine, no issues, runs like crap....

I wouldn't say complete crap but definitely a noticable hesitation and seems to bog on the hwy when you get to a hill.

Next on the list:

Check ignition coils, does anyone have specs on resistance?

Intake shutter valve, reports of sticking and recalls, if I take it apart will I find an obvious problem?

Fuel pressure/cleaning injectors - Any procedures for testing pressure?

I am pretty mechanically competent and have all common tools so I have no problem tackling jobs like this ( for reference I did a 12 hr timing belt replacement on my Tundra)

I just can't stand spending $150 at a dealer for them to tell me nothing's wrong, that's just the way they are.... On that note, anyone have recommendations on a Mazda shop in New England that may actually be competent to diagnose this?

Any input or suggestions greatly appreciated.

Bill

 

[Straeliterun]

It almost sounds like the throttle response time is an issue...which might be why it bogs on the highway hills and doesn't downshift (I am figuring it's an auto). I know I've read that the grounding of the TB is supposed to help that, but I've also read it doesn't matter due to the particular setup of the tb they have. Maybe theres an issue in the relay from the pedal through to the TB. I also thought they were programmed to have a little bit of lag time there to keep the car from being too jumpy in the first couple of gears. These all all just thoughts as I sit here at work and read this so take them with a grain of salt! I think basically its just a few more things to read about.

 

[bbrich57]

Just throwing stones myself here: Though you don't say it does sound like you have an auto. Could it be the automatic trans thats the issue and not engine/throttle response?
I have always driven stick shifts myself, so I don't know a lot about autos, but have read of a sensor/actuator/valve that can cause sluggish activity and/or bad shifting if not working correctly.

*edit* Also when you cleaned the MAF did you spray clean the inside too, or just the dew drop that you can see?

 

[Throttlemonkey]

Sorry, it is a 5 speed.

I sprayed the vleaner all i side the unit as best as i could, it looked clean anyways so i doubt that was the issue.

I disconnected the battery, let it sit 20 min and reconnected. It seemd to run better for a day or so but now it's back, not sure if it was placebo affect or not......

 

[bbrich57]

Does it idle badly? Stall at intersections, etc?

 

[Throttlemonkey]

Nope, idles nice, never stalls.

I am also starting to notice it is worse with the AC on, not sure if that means anything....

 

[oaklandopen]

Lack of torque, get a mazdaspeed ......jk

Actually, if you have a scan tool with recording capabilities tou could just do a live data recording. I have a $180 craftsman obdII scanner that does that, although I probably should have just shelled out more dough for a dashhawk or something better

I had an 07 gt 5spd for a while but don't remember feeling what you're describing

As for coil resistance, id just compare them to each other if you can't get specs (I'm not where I can get to the factory repair manual right now)

Isn't there a testing port on the fuel rail somehwere so you can hook up a fuel pressure gauge? If not, an obdII reader can tell you that. As for individual injector cleaning...there is only 1 good way to do that. Take them out and put them in a machine that not only cleans, it tests the cycles and spray patterns. Or you could throw some seafoam in your gas tank

If no codes pop up when this happens, and none are stored, it might just be a normal thing.

 

[Straeliterun]

The ac thing is pretty general to any 4banger to some extent. And as for a competent mazda shop...idk. I live down in ct, and only let the one I use change the oil and thats pretty much only because they're in a convenient spot. Check the NEPOC forum though. Its down near the bottom where a lot of the local area threads are.

 

[Throttlemonkey]

I just sold my 98 civic that had abot 62 hp, I could run the AC in that without issue......

Just a little disappoionted I guess after buying this car based on all the great reviews.

 

[MazdaSwede]

I just sold my 98 civic that had abot 62 hp, I could run the AC in that without issue......

Just a little disappoionted I guess after buying this car based on all the great reviews.

You traded up trust me. Every car dealer has a few that something goes wrong during production. could just be you drew the short straw.

As for bogging. i don't have that issue and everything in my engine is stock with a manual 5 speed. If i were to guess id say youre not downshifting as you start up. its what i do and there is no hesitation. next time you go up a hill drop it a gear and see if it does the same thing. Not saying you don't know how to drive just giving my two cents.

 

[Throttlemonkey]

Been driving nothing but standards for 35 years, I'm all set......

The stumble is the worst between 2500-3000 rpm which should be well with the normal operating range even for a 4 banger.

 

[bbrich57]

That's right about where the VVT comes into play. Hmmmm..... Could be?