- January 9, 2021 at 5:09 pm #281954TJScanlonParticipant
I am a brand new subscriber and trying to learn but drinking out of a fire hose right now so looking for a little guidance from you who have more experience.
2008 Mazda 6 iSport (2.3L 4 cyc) with 148k miles. Just purchased from my neighbor with my 16 yr old son as his first car. Neighbor was original owner and had car maintained mostly by dealer or independents. He doesn’t know cars but it had all basic maintenance done. We purchased for $1,200 – neighbor didn’t want to sell as he didn’t want to feel bad if something went wrong. I want stuff to go wrong a little as both my son and I are learning on this car:-).
We have done work on the car – new front brakes/rotors, repaired plastic bumper tabs, replaced headlights (they were yellowed and we couldn’t polish enough) and replaced the valve cover gasket (leaking oil) and plugs. I double checked the hoses we had to disconnect and they seem connected.
There really haven’t been drivability problems that I have experienced.
I was getting codes P2177, P2187 initially. I cleared a couple times and they came back and now am also getting codes P2097. All three codes are present.
My son and I removed the MAF sensor and cleaned that using MAF cleaner. It was dirty. The screws holding it into the top of air intake box are stripped so it is not tight. It seems secure but I can wiggle it a bit. I tried propane around it and other accessible areas to see if we could detect vacuum leak but I could not get a response.
Using BlueDriver live data on a warm engine parked.
At idle 750 RPM
At 2000 and 3000 RPM
When taking foot off accelerator within 3 seconds
STFT 25% to 0% and then back to 25% within 3 seconds
LTFT 0% this does not flucuate
O2 goes from 0.965v to 0.8v back to 0.965v
I am too new to this and this is my first time making these measurements so I am not sure what I am really seeing. Having watched the video on Fuel Trim it appears my 02 sensors is maybe showing a rich condition? It also appears that the STFT is maxed out at 25% but it hasn’t reached equilibrium so the LTFT has not reset? I don’t know what this means as far as where to look.
There is a hose under the intake manifold which can be a problem on my generation of Mazda 6’s. To get at this hose (and I believe the PCV) requires removal of the intake manifold which is fairly involved (for me). I would love to tackle it but it is cold in Minnesota right now and was hoping this would be a spring-summer project:-). I ran propane over where the intake manifold is attached to the engine and could get no reaction.
My thought was vacuum leak but I can’t find anything obvious so maybe I am way off base.
I can get more measurements and have a multimeter. Would love to get some advice from everyone on where to dig.
MinnesotaJanuary 9, 2021 at 9:01 pm #281956ApexParticipant
I replied to your intro post, but I posted a link to another forum with a suggestion on your MAF housing issue so I believe it has to wait for admin approval first.
It sounds like you are not dealing with a vacuum leak as typically in the case of a leak you will see a fuel trim improvement at higher RPMs. As for why the LTFT isn’t going anywhere, every manufacturer does their programming for when LTFT adjusts differently, so keep an eye on it, but in one case I believe Matt got burned on a reading where he only looked at the LTFT and the STFT was stuck lean or something to that effect, so it’s always important to look at both for a total fuel trim.
I had 3 suggestions for repair on my other post which I’ll repeat here for good measure if you wanted to fix the stripped screws, but the propane test was a good idea, assuming it would have fed enough to reduce the trim, did you try feeding a small amount of propane directly into the intake to see if it would show up on your fuel trims just as a sanity test? The first suggestion was what I linked to on a Mazda RX8 forum where they drilled out the plastic housing and used threaded inserts instead, you can google “DIY: Fix your MAF screw holes for $2.26” and the exact thread I was looking up will come up. I am assuming this will work on the Mazda 6 housing, but you will need to compare to what the 6’s housing looks like and see if this will work for you. My other suggestions were to either melt new plastic in there or use some sort of soft epoxy to fill in the hole, then carefully drill a new, straight hole and use your screws to cut into it.
You could have a lack of enough fuel or a bad reading from your MAF among some other possibilities, but a vacuum leak is actually unlikely in this case (or at least it is not the only contributor). Are there any drivability problems or just the lean condition? What do your MAF sensor readings look like on and off idle? Also, I would graph the O2 sensor signal to see if it is oscillating, it would be odd for it to be stuck at 0.9v when in a lean condition as that would indicate a rich condition or bad o2 sensor, unless you are looking at the rear o2 sensor anyway (B1S1 = Upstream, B1S2 = Downstream).January 9, 2021 at 9:56 pm #281957TJScanlonParticipant
I am trying to get my head around all the readings, what they mean and how they relate. I had just watched Matt’s video where he talked about getting burned not looking at both STFT and LTFT – in it he had showed the O2 as high but noted that it should be low for Lean condition so my O2 was showing rich.
I will be looking at MAF readings tomorrow. The O2 sensor was B1S2, I have to believe my BlueDriver can read the B1S1 sensor but I must not of selected it during live reading. My BlueDriver OBD reader I am not sure reacts fast enough to see the oscillation in live setting. When I save the data is stores in Excel file and appears to take measurement every 0.5 seconds. As I get into this more I will need to look at a better diagnostic tool.
Really appreciate the lead on the MAF screw hole repair. The post hasn’t shown up yet but will check it out when it does – I was thinking the epoxy route but would like to check out the threaded insert before I go epoxy.
Thank you so much for taking the time to reply – I really appreciate the help!
- You must be logged in to reply to this topic.