Mazda Tribute issue...

[Macca86]

Firstly, if this is more suited to another section or not at all mods please move or delete.
Just tearing my hair out with this so am after any advice my anyone mechanically minded on here
My sister has a 2003 Mazda Tribute V6 Auto. And it has a problem that ive been trying to fix for her but have come up with nothing
The problem is when its in overdrive, and at around 1,800-1,900rpm and you lightly accelerate (say at a slight rise in the road) it starts missing irratically and spluttering. If you put your foot down hard enough for i to drop back a gear, then its fine. Idles fine, runs fine and has no issues other then the previously decribed conditions.
Its had a new fuel filter, and new spark plugs. Have had it hooked up to dianostics at Mazda, and it has no error codes of any sort. Its been pressure tested, and each cylinder has been leak tested. Thought it could be a coil but this would have been indetified when hooked up to dianostics.
Anyone have any other ideas?

[CSP]

Dirty injectors maybe. How many kms?

Also, maybe try a Mazda forum?

[Macca86]

Yeah I just ran an injector cleaner through it this arvo. See if that makes a difference at all. Has about 150,000km on it.
And yeah I have it posted up on a few other forums, just thought I would post it up here as well as I know ther are a fair few mechanics etc on this site. Using all my resources so to speak. lol

[Asmodai78]

go check out the ford forums and look for the ford escape as they are one and the same

[Tsunamix]

Lets try a bit of logic, see if this helps.

Doesnt miss under heavy throttle under load.
Does miss under light throttle under load.

Difference is fuel volume provided to the cylinder, and / or timing of injector pulse and / or spark timing issue.

Timing of the injector pulse can probably be ruled out. Would take a catastrophic failure across a few systems to do that.

related to fuel volume - what is the Fuel pump pressure and is it consistent across the rev range ? Is it electrical or mechanical. ?
Often there is a light loads injector map and a heavy loads injector map in the ECU. Quite possibly one of the sensors that helps determine light loads is faulty, and reporting no load so lesser fuel is injected - leading to lean out.
Your cleaning the injectors but a dirty injector makes more sense if it was missing a heavy loads.

Spark timing - usually controlled by the ECU. You may find that a crank angle senso is faulty, reporting a retarded crank position relative to the spark. This would cause a miss under lght loads. If it only occurs in overdrive there may be some sort of mapping in the ECU that switches to a highway economy cycle when in overdrive, and retards the spark. When you stick the foot in deeply the Map detects teh wide open throttle and advances the spark for performance / overtaking, but under light loads leaves it retarded for economy. If the CAS is faulty you might be seeing an over-retarded situation.

To be honest I don't even know if the Mazda tribute has a CAS, but it would have to pick up spark timing relative to something.

I would be starting with the possible Crank Angle Sensor, and failing that it would be back to an auto sparky to have a look at the fuel map - assuming your fuel pump isn't mechanical and doing something bogus at lower rpm.

Good luck

[illusionalvr]

like i suggested to someone else, disconnect the battery for a little while. let the car reset itself.

[VL Executive]

Could be a MAF or air flow meter problem.

[CSP]

a MAF is an Air Flow Meter.

[Macca86]

Cheers for all the replys guys. Was about to go down the path of what Tsunamix suggested with it being a problem and check crank angle sensor and ECU maps. But as of at the moment, seems to be running fine after cleaning the injectors. Will see how it goes and if the problem returns. Could have been something else still as we had the whole thing pulled down checking the head etc and may have re-set something electrical when all was connected up again. See how it goes anyway. Cheers guys