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We bought a Mazda MPV 2260cc 6 months ago 2 months after we bought it it started surging and got really bad we had it serviced at Mazda in Timaru, they changed the air filter and the throttle body cleaned and oil change, it didn't make any difference. We bought new spark plugs, still no change, We took it to an Auto Electrician and they put it on a diagnostic machine said there was nothing wrong with the electrics, but they put new spark plugs in again as they said the ones we got from super cheap weren't the right ones!!!. then they found a plastic butterfly in the throttle body was cracked so they got a new one. Since then we got a bill from them for $1309.00 and it is still surging!!!!! have you any idea what it could be?? Thanks.

Sometimes faults such as this can be very difficult to diagnose and until one thing is corrected, you can't move onto the next.
Having said that, there are so many things that can cause surging. Air leaks, ECU faults, throttle body problems etc would all be potential causes.
You don't say under which conditions it is surging. Is it under lean cruise, when it's cold, hot, at a particular speed etc? These are all helpful details to help your mechanic track down the problem.
Certainly, I'd suggest that you stick with the same mechanic, so he knows what has been done up until now and can get a clear understanding of what is occuring and when.
Sorry we can't be more help.

Hi there, I have been having the exact problem with my 2003 Mazda MPV. I did have a broken butterfly on my intake throttle body, got that fixed, replaced plugs etc, did the full monty service and tune. But still surges. Acceleration fine, deceleration fine, 50kph low rev fine, but if im going down the motorway at 80-100kph at a low rev, say around 2200rpm the car shudders a little like its misfiring. It is only slight, but really annoying. I have had the motor on an electronic diagnostic and they couldn't find anything. Could it be a transmission issue?

hiya just thought i would tell you that i took mine to another mechanic and he told me mine is surging and also has a flat spot upon acceleration because it has a air leak, possible on one of the joins in air hoses,it also does what yours is doing as soon as it gets to about 80-90 kms it plays up . am going to get mine repaired soon, cheers

Hi Kevin, thats interesting, could be the exact same fault. Your not in Wellington are you? I would be interested to know how you get on. I think I will have another look under the bonnet for hose damage and get mine looked at also. Keep in touch.

I would be checking for an air leak in the intake manifold. They are plastics has have been known to crack on occasion around the casting marks and the joins.

Also, check the crank pulley is tight. They don't have a key way on them so if the bolt starts to loosen the timing will start to slip