Random 3-4k idle then failed to start

[bunka T5]

Ahoy.

So, my idle has been random since I got the car a month back, would be between 900 to 1.1k (ish) most days after driving..
Today however it was a bit odd, after driving to a destination and leaving the car parked for about 30-40 mins, then starting back up and let the car idle for a minute or two the idle /revs shot up to about 3k,
I let it continue for about 10 seconds to see if it would settle but no avail so I shut it down, checked under the bonnet (always my main plan of action) checked coolant, under the filler cap, dip stick, nothing smelled hot or over heating. Then tried to fire her up again and just turned over. Tried several times, nothing. Left it for about 5 mins and then tried to crank it a final time and it finally started with a slight bit of hesitation.

Continued to drive a bit more and its been completely fine, even did a few test stop / starts and again no issue. I've not let it idle for more then a minute before shutting it off yet, however. I've read someone had similar issue here - (http://www.matthewsvolvosite.com/for...hp?f=1&t=21479)

Does it seem likely?

- Volvo 850 t5 96'

Cheers

**awaiting a link to a Robert DIY video** :p

[bunka T5]

Bump, no one ?

[R-200vi]

Bit of a job to know with out looking. I do know the temps sensors do cause all manor of crazy things. Also if you look on the side off the inlet manifold where its closest to the power steering pump there is a core plug with a vacuum pipe coming off it, They often give air leaks. Maybe give the idle control valve a clean out.

[MaxTS]

We gave the idle control valve a quick clean and replaced the thermostat and it seems better after it got up to temp again, as it was not happy after we first put it in.

[R-200vi]

If it is the temp sensor it probably will seem to run better when warm. See what its like from a cold start and run upto temperature. Did you check the vacuum pipe on the side of the inlet manifold?

[bunka T5]

I've not checked that vac pipe on the inlet mani, no, gonna get my head under there again later.

I've done 3 'cold' starts, ie been parked up for 6-12 hrs before re starting and shes been absolutely fine, idle is a bit lumpy at times however. New ICV ? I'm going to change the temp sensor regardless though, as I think that looks like it needs a change, and it takes minutes to do.

The high over revving / failing start was DEF the Thermostat! There was a 'sweet spot' while warming up or cooling off where the cars revs would just rise, while driving, parked, whatever to like 3K for about 20 secs then as it got passed that temp it was ok(ish) again.

But like I said, that particular issue is now completely gone with the changing of the thermostat.

[bunka T5]

How would I change topic to 'SOLVED' so as to benefit others with same issue ?

[jamesy12345]

How would I change topic to 'SOLVED' so as to benefit others with same issue ?

Use the tags mate, people will find the thread easier and read through:

[bunka T5]

On another update, the problem came back, so I actually got round to replacing the Engine coolant Temp Sense (as was initially advised, before multiple different ideas eventually confusing me hurr durr), and that 100% fixed the problem, been 2 weeks now and not even a hint of that issue has re occurred !

[MaxTS]

On another update, the problem came back, so I actually got round to replacing the Engine coolant Temp Sense (as was initially advised, before multiple different ideas eventually confusing me hurr durr), and that 100% fixed the problem, been 2 weeks now and not even a hint of that issue has re occurred !

Good, glad it's finally sorted! How has the power cut/restriction been on boost?

[bunka T5]

I'm starting to wonder if its to do with badly blocked PCV, so I'm not booting it at all till I sort it, ala blue 2.5t ended up buggering the engine, pretty sure the oil in that wasnt recirculating