Subtle hesitation with acceleration

jsilva

jsilva

Greenie N00B Member
Greenie Member
I’ve noticed a subtle hesitation when accelerating at lower RPMs, somewhere around 2000-2500 under light to moderate throttle. It feels sort of quickly jerky, but it’s so light even passengers don’t really feel it. It’s not all of the time, but seems to be more when warming up. And it’s never there with full throttle at higher RPMs.

Any thoughts as to what it could be?

Edit: I just realised I now have an accessport so tomorrow I’ll try and get a log when it happens.
 
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I got some logs today but wasn’t sure it was happening then. Later I felt it for sure but didn’t have the accessport connected. I won’t waste time posting logs when I’m not sure it’s definitely happening so I’ll try again in the next day or two.
 
I’ve been paying close attention and I think I got it wrong. I don’t think I’m feeling hesitation with the engine but rather a vibration or pulsing when accelerating under certain circumstances.

It’s mainly under moderate acceleration and I’m beginning to wonder if it’s more pronounced when things heat up. I looked up possibilities and these seem to be the most relevant:

CV axle
Motor mount

I replaced the driver’s side CV axle when I rebuilt the engine (torn boot spewing a lot of grease) but not the passenger. The passenger motor mount is old. So those are possibilities.

But I wondered if it could possibly be the transfer case (MS6) or transmission.

Any thoughts would be appreciated.
 
I spent some time today narrowing it down.

1. It appears to only happen in 2nd gear.
2. It appears to only happen between 2000-3000 rpms.

I've attached some logs for anyone's diagnosis—1st, 2nd, and 3rd gears from 2k-3k rpms. Not sure they show anything, but it'd be good to eliminate the engine as a cause. It definitely happened during the logging for 2nd gear and not the others.
 

Attachments

After more time has passed I’ve noticed that the vibration seems to happen only after things have warmed up—after driving for a while with some speed (rather than the engine warming up).

My best guess right now is that it’s one of the front CV axles. The passenger side has a tiny bit of up and down play at the transmission side. It seems to me to be within acceptable range although the driver’s side (a new DTA axle) has no play in that way.

So eventually I’ll replace the passenger CV axle.
 
The other day I replaced the passenger CV axle with a Mazda remanufactured one from the dealer (seemed excellent quality). That appears to have cured that vibration.

For what it’s worth, I don’t think either the driver’s or passenger’s CV axle which came with my car were Mazda axles.
 
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