At a loss - Idle problem at high temperature

[mistryman]

Hoping someone can shine a light on an idle problem on a 56 plate with 90k.

Car starts fine and runs sweet until it gets to higher operating temperature - my temperature gauge normally sits at 80 but rises to 90 when in stop start traffic - has always been like that.

Symptoms typically occur after about 25 mins but not always - last week ran fine for several days with no obvious idling issues.

Once it get close to 90, starts sounding rough and revs start to climb to 1200-1500 and then drops back to 800 and continues like this. Feels a bit spluttery and jerky when in this state.

Have ran the car with the MAF disconnected and ran better (no idling issue) but prone to stalling when cold, however the MAF has been tested and  working as it should.

Had a diagnostic specialist give it the once over but he's at a loss as it seems to be an intermittent fault and reckons symptoms needs to get worst before it can be pinpointed. Doesn't want to go changing parts in the hope that it fixes it.

Could a faulty temp sender cause such symptoms? Anyone else had similar issue and what was the fix?

Any help would be gladly appreciated!

[fab5freddy]

Have you checked the PCV? Very common on these engines and would be my first port of call, given the symptoms described. Do a search on here, loads of threads about this.

Also looks like your main stat is fooked, again a quick search will show its a common problem 

@mistryman

[mistryman]

Cheers @fab5freddy

PCV been looked at, that's fine. Also reading the various threads on that, there no mention that symptoms occur at higher temperature.

Think temperature sender may be first port of call...