Engine Idle upon cold start, smoot 20 seconds, rough 20 seconds then smooth

No driveability issues otherwise? RPM drops smoothly when put into drive? Shifts fine? Throttle response? Will it idle smoothly and/or run normally if you manipulate the throttle/off idle? Did the CEL come on during the rough running event?

I'm betting a problem with the throttle actuator, but it could be an input or output from PCM. Unless it's had the battery disconnected, codes will still be in memory/storage in history, if not pending active codes as well depending on how frequently this happens. Did you take it to the dealer with this specific complaint or just because it had a CEL show? If the latter, that could be your problem, i don't know if a licensed guy did it or just one of the oil change guys. They could have just done a scan and seen no active codes and unplugged the scan tool.

It would be easiest to diagnose if this can be replicated every cold start. Give me a little more info. We'll get to the bottom of it.

At this point many things could cause this. EVAP purge solenoid, bad PCM, O2 sensor going out, coolant temp sensor bad. Being this problem is 90% an electrical or electronic problem, it doesn't matter how new the car is. It's really luck of the draw as to which cars get built with sensors/electronics that last forever (my 07 for example) and those that need to be replaced prematurely.

Thanks!!!!

Dear Versa/Tiida Comrades, especially 07Versa6MT and rstolz,

I heartily thank you for all of your imput in regard to my problem with the Tiida.

You have created an excellent list of possible causes for such a problem, and as a result, I believe you have done the board a great service.

As for my particular instance, I took the car back to the dealer again a second time (Nami Nissan, Pachuca), and told them exactly the same thing that I indicated here in my original post. And this is what they say they did:

1) Removed and cleaned the original spark plugs and reinstalled them as it was not yet time to replace them and they did not look like they needed to be replaced.

2) Cleaned the fuel injector nozzles.

3) Told me to use premium fuel, as the regular fuel around here tends to be a bit mucky.

Result: Now everything seems to be fine. We took it on a road trip this past weekend and it ran like a champ, including just after start-up, and has run fine after start-up each time since getting it back from the dealer this second time.

I think the take-home lesson for me is, that even with our post-modern-frighteningly-technologically-advanced-computer-on-wheels-with-an-internal-combusion-engined cars, sometimes the fix for some problems can be something very simple

The really amazing thing is that they charged me 500 MXN (Mexican Pesos, the car is no longer on warranty), approximately $38.50 US, the first time I took it to them, and they charged me NOTHING the second time, when they actually worked so hard to fix the problem.

Nissan is #1 in both passenger car and light truck sales here in Mexico for a reason!

Thanks again for the responses!!

Hey 07Versa6MT,

I was suspicious of their claim to have cleaned the plugs because I know it is a lot of work to get to them, but as soon as I drove away I knew that they had done something because it ran better. It could be that they chemically cleaned the plugs. It could also be that they used a wire wheel or some such. The car has 67,500 Kms on it, and according to the maintenance schedule for Mexico, the plugs are due to be replaced at 80,000 Kms. Perhaps they figured they would soon be replaced anyway. I suppose the change at 80,000 Kms is a concession to the crappy gasoline around here, as the US maintenance schedule calls for them to be replaced at 100,000 MILES.

Generally, in the North American experience, premium gasoline shouldn't be any cleaner or more suitable for an engine made to run on 87 octane fuel than regular, but here the oil refinery capacity is so inadequate that most of the premium gasoline sold in this country comes from the USA, so maybe it is more suitable.

Anyway, for now I will do as they suggest and see what happens.

Thanks again for all of your help.