2005 Mazda MPV Uneven Acceleration

Tiny
GULFGOLF
  • MEMBER
  • 2005 MAZDA MPV
  • 84,000 MILES
Ok, I'm gonna be as detailed as possible for ya.
Bought our 05 MPV used with approximately 72k and she ran just great. We are sitting just over 84k and there is this ongoing issue that I've yet to fix.
The uneven acceleration is evident at both start up and throughout any short or long drive. Any spirited acceleration, under load, will usually result in a "lumpy" or uneven gathering of speed. It hasn't affected our mileage- I still average just under 20 mpg with a mix of urban and rural driving. I've replaced all 6 of the COPs along with the spark plugs(OEM) and also the PVC hose and valve that are very prone to failure. I've replaced the air filter with a K&N and cleaned throttle body and the MAF and IAC sensors. The transmission fluid was changed as a last ditch hail mary- no dice however.
When I replaced the COPs and the spark plugs the upper intake manifold had to be removed, so I changed out the gaskets for the upper plenum, throttle body, EGR valve and IAC. What gives? I must be missing something- but it isn't throwing any codes I can reference for you guys. I know you'll mention vacuum leaks- and if you think it's still the case I'd like a tip or two on detecting them- the throttle body cleaner around all the vacuum related parts while the engine is idling and listening for errant sucking sounds or a surging idle isn't doing the trick. Thanks for your time and expertise!
Do you
have the same problem?
Yes
No
Saturday, July 6th, 2013 AT 4:20 PM

3 Replies

Tiny
KHLOW2008
  • EXPERT
If problem is engine performance related, it should not be anything to do with vacuum leaks as vacuum leaks would affec the idling.

Hesitation under load are usually due to problems with ignition system and since you have replaced the spark plugs and coil packs with no difference, that eliminates them as possible causes.

If you have a scan tool, monitoring the TPS couls teel you something.

On the other hand, if it is not performance related and you have vibration sensation while accelerating, have the drive axles checked. The inner joints could lack lubrication or are worn resulting in vibration during acceleration.
Was this
answer
helpful?
Yes
No
Sunday, July 7th, 2013 AT 4:01 AM
Tiny
GULFGOLF
  • MEMBER
Thanks for the new leads! But to clarify- the van doesn't have any other performance issues. There aren't any drivetrain vibrations or transmission issues. It shifts smoothly and strongly all of the time. It also idles fine and there aren't any extra noises while it is running, that I can detect. It is interesting that you mentioned the TPS- I'll check it as soon as the rain dies down. While driving and accelerating briskly, my wife says that it looks like the tachometer isn't swinging smoothly- as in it climbs with the revs, but during the unevenness it'll pause ever so slightly- so instead of a smooth arc from lower revs to higher RPMs it appears to stutter in time with the sensations we feel by the seat of our pants. A bad COP was my first guess- mainly because it felt so similar to what happened with our old Crown Vic, abjectly however it feels a lot more subtle on the van we have now.
Anything else come to mind? I've got nothing going on now- its raining cats and dogs here in the Panhandle.
Was this
answer
helpful?
Yes
No
Sunday, July 7th, 2013 AT 1:16 PM
Tiny
KHLOW2008
  • EXPERT
Have the fuel pressure tested. If fuel delivery is insufficient, it can result in loss of power during acceleration as well.
Was this
answer
helpful?
Yes
No
Monday, July 8th, 2013 AT 7:18 AM

Please login or register to post a reply.

Recommended Guides