I have two minor nuisances with my 2004:

1) Vibration when the idle settles to it's lowest point. It's perfectly smooth once a few hundred rpms above (900+), but at 700-800 you can feel it vibrate.

2) Maybe 1 in 20 starts will take 2-3 seconds instead of the usual 1 second. Not a big deal, it doesn't seem to struggle, just seems to take an extra second or two before it gets fuel. But it makes me think something has an intermittent problem.

FYI, the engine was replaced 10,000 miles ago, along with the plugs, coils, wires, engine mounts, O2 sensor, battery, battery cables and clutch. The starter is the upgraded one replaced in 2007. Cleaned the MAF. Air filter new. The vibration and occasional long start were there before the engine swap and after. No CELs. Runs perfect otherwise.

A number of people here have suggested I might have a leaking or sticking fuel injector. And when the car wouldn't hold an idle after the engine swap, the Mazda mechanic suggested the same thing (it eventually sorted itself out). He also said it was "running rich" after the swap, although maybe it was just relearning as the CEL for it stopped a few hours after the swap.

But it all makes me wonder if a fuel injector is acting up and causing all these little nuisance issues. I can't work work on the car myself, so I'd have to take it someone. But what do I ask for to have injectors diagnosed? Is it possible for a Mazda mechanic to test them, or must they just be swapped for new? Is it insanely expensive to have them tested or replaced? I see the injectors aren't cheap, but I don't know how much labor is involved?

 

My 2006 did the EXACT same thing.. more frequently than 1 in 20 and when people got in my car the idle vibration would make them ask if somethings wrong with it.

We replaced all the coils, plugs, and wires and then seafoamed and the car changed a TON. I don't see why yours would need any of that though if you're on a new motor?

 

BUMP

I'm now being told my fuel injectors have an internal leak. Is that possible and are they able to 100% able to diagnose that is what is in fact happening? The dealerships "suspects" that is what is happening and want to replace them for $1,200....