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Mazda 3: rough idle after head gasket repair

I recently had $1600+ of work done on my 2005 Mazda 3 (L4 2.0L). R&R Head Gasket and Thermostat and Coolant Temperature sensor replaced. Since then it’s been idling roughly. This was NOT occurring prior to the work. Mechanic says it needs a couple of weeks to “synch”? Does this makes sense? I’m wondering if they did something wrong to cause the problem.

Thanks for the advice!

It doesn’t need a couple of weeks to "synch"
Did the shop reset the keep alive memory? They should have, after such a major repair.
Perhaps a vacuum hose was left off . . . can you hear any whoosing or hissing noises from the engine at idle?
Your idle air control valve may be faulty . . .
I recommend you take the car back to the shop with your concerns.
But you already did that, right?

By the way, why were the head gasket, thermostat and coolant temperature sensor replaced?
Did the engine overheat?

From Your Description, They Did Something Wrong.
CSA

What was it doing that it got a diagnosis of bad head gasket ??

No, the engine didn’t overheat but the engine light was on and the AC didn’t work. We took it to two shops and both said the same thing. We have taken it back twice and they’ve said the same thing. So what recourse do I have if they don’t fess up that there’s a problem?

Rough idle could be a leak somewhere in the intake manifold which had to come off to replace the head gasket. The shop had to take most of the top of the motor apart to access the head. There is a leak somewhere and they just hope they can put you off and hope it seals itself over time. Not likely at this point.

Was it a dealer that did the repair?
So, you’ve sat down with them and discussed your “difference of opinions” and they’re still blowing you off, so to speak?
If it was a dealer, contact the regional manager, since I assume you’ve already talked yourself blue in the face at that shop.
Just a suggestion . . .
Regional managers have the power to make things happen.

Thanks for the helpful replies! It turns out that the car WAS doing the rough idle before the repairs. Our son neglected to mention that until now. They are saying now that rough idle is vibration because we need new engine and transmission mounts.

So are they going to refund you the $1600 for the “head gasket”??

So what happens if they replace the mounts and it still vibrates? Based on the utter load of carp (sic) synch thing they gave you the mount diagnosis might be suspect as well.
:frowning: