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I still think its the ecu, perhaps theres an intermitten fault with throttle body drive motor, perhaps a resistance and insulation test may be in order to rule it out. The rich code would be because of the slow opening. Maybe send it to an autoelec before deciding to get rid of the car.
 

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I tried that procedure on my car and no difference. You could try a new throttle body. I'm sure the electric motors in them get lazy with age. They run $75 on ebay. One other option is one of those throttle pedal modifiers. They should increase the rate the pedal opens some. There are some generic china made ones that are relatively cheap ~$70.
 

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Discussion Starter #23
Okay, so I think I finally have this problem licked. It was the mass air flow sensor. I pulled it out to look at it and it was absolutely filthy. I've never seen one get that dirty. The coating of dirt on the filament was so thick I couldn't see the wire until I sprayed it off. The car actually ran worse for a bit after I cleaned the sensor but it started to clear up after I drove it some. The initial cleaning was done with a can of starting fluid yesterday because it's all I had in the shop. I just took it out today to get some actual cleaner and run some other errands and it ran fine. I took the sensor out just a few minutes ago, cleaned it again with the proper cleaner to remove any residue from the starting fluid (upper cylinder lubricant), blew it off and slapped it back in.

I took it for a drive after that and ran it through its paces. I couldn't get it to do the same behavior again, which is such a relief. I can even blip the throttle for downshifts now. The low RPM torque is plenty for normal driving, and it does what I want up top as well. Thanks everyone for the helpful tips, especially Xalint6 with the MAF sensor suggestion. I never would have thought a dirty MAF would do this, although some of the other issues I had when I first got the car may have made this seem more complicated that it was. Lesson learned.
 

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Did you take a photo of that dirty MAF? Would like to know how it got that dirty. 290,000 klms on my 4x4 through mud dust sand snow fire.. still clean as a whistle. Perhaps previous owner removed air cleaner and did circle work in an old shale oil mine.
 

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I agree. I've never even seen any visible dirt on all the ones I've inspected up to this point. I didn't take a picture unfortunately, but I can say that it was like a sweater of dirt on the filament. There's a bit of a history on this car that I haven't talked about yet. The guy I bought it from said the original motor blew, and that the engine and transmission was out of another wrecked Mazda 6, which he showed me. Neither were his cars originally. It's possible that the dirty MAF had something to do with the old engine failing. Maybe it was run for some time with no filter for some reason. It could also have been from an over-oiled K&N filter that might have been on one of the cars, as I've heard they can cause some build up. Who knows though.
At any rate the car runs like a dream now. Before I tracked down this MAF issue I had problems with the fuel pump and one coil failure, so it's got brand new coils, plugs and fuel pump. Every time I drive it now it seems to run better. I rarely use more than quarter throttle now and I usually have a bit of a lead foot. I'm very happy with how it drives and so I won't hesitate to sink more money into some of the nit picky stuff that it needs.

Did you take a photo of that dirty MAF? Would like to know how it got that dirty. 290,000 klms on my 4x4 through mud dust sand snow fire.. still clean as a whistle. Perhaps previous owner removed air cleaner and did circle work in an old shale oil mine.
 
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