1995 Micra runs well when cold but gets rough and lumpy when warm?

[Charr]

Strange problem
It runs great when I start it from cold and gradually gets worse until the first bar on the temperature gauge
Exhaust smells Catalytic-ish when it does this but not before, it can even rev up good until this point.
Disconnected O2 sensor, no difference
Noticed yesterday after putting fuel in it would get rough when lights on, then it started holding back on acceleration, it has rapidly gotten worse since then.
Fuel economy a bit trash for a while, could be the corroded fuel filler neck though

Disconnected MAF sensor, no difference either
Possible hissing but could be air flow

 

[FinnishCoffee]

According to your suggestions, i'd check a couple of things out first, all related to the throttle body: (don't mind if the instructions state one or another version of the engine, the 1.0 and 1.3 versions are 99.9% identical)

• Check the waxtstat idle mechanism
• Check and clean the IAC valve (both covered here)
• Resolder the throttle body airflow meter (with this great guide from the aussies that also has great steps for getting to the throttle body)

Not completely sure these will solve your problems but these should be checked out for any K11 regardless.

 

[Charr]

That's quite complex for someone of my skillset lol (also I don't have a Datascan unfortunately)
Anyway I've got it in for works on tuesday, maybe they'll figure it out

I may attempt these things afterward if I feel like it, I don't mind a good try

 

[FinnishCoffee]

Tbh, you don’t need a datascan if you don’t adjust the valve, and aside from the soldering bit everything can be done with a couple simple tools. I guess soldering can be intimidating for someone who’s not used to it but hey, you never learn if you never try.

Good luck with that anyways, hope you get it sorted out!

 

[Charr]

In the end it was water in spark plug one
She's happy now
why did this happen?
I may have washed the engine too thoroughly