My 850 is driving me nuts...(engine stalls when hot)

[TWC]

Holiday! Yay!

And finally some time to fix a few things before it's time for the inspection. But there is one issue which is really annoying the hell out of me (and the others being sometimes involuntarily caught up when it happens):

After driving around for a time, the engine stalls sometimes when either stopping (e.g. at a traffic light) or driving rather slow with the throttle in idle (coasting) at low rpm. After waiting for a few secs, the engine starts again, but is likely to stall again when described conditions occur. Exception: starting the cold engine and letting it just idle, no stalling.

The things I did so far:

• replaced oil catch, cleaning the hoses and lines
  replaced the flame trap, also cleaning the whole stuff
  cleaned the MAF and ICV
  fixed the flap of the air intake in "summer" position (at currently 35°C outside...)
  replaced the radiator
  replaced the thermostat
  cleaned and oiled the K&N filter to specs
  replaced the ignition coil and cables

and a few more things I probably have already forgotten again. Some things I did brought slight improvements, but the main problem persists. When I open the hood after driving I think that the engine bay emits a lot of heat, but the engine temp seems to be okay.

Now I'm stumped. Any other suggestions?

[RickHaleParker]

Check for leaks on the intake manifold. Spraying starting fluid around it and listening for a engine surge is the easy way.

[erikv11]

I agree this sounds like a vacuum leak.

Especially check the little bracket that holds the injector wires near cylinder 5, is it lodged under the edge of the manifold? Common problem following oil trap service.

The flame trap itself (little disc with holes in it) I would just throw away if you are in the area while doing this work. It adds nothing except a great place for the PCV to get clogged up.

A troubleshooting test: unplug the MAF before starting the car, drive around with no MAF. It will set a MAF code but should otherwise drive fine. If this solves the stumble issue, then the MAF is bad. Unlikely but possible and free to test.

[Oitsujosh]

Twc, when was the fuel pump relay last replaced? I had a similar issue last summer on my 98xc and that was the culprit. It would only act up after a longer drive on days above 75-80 degrees Fahrenheit and was driving me nuts. After changing the relay has not done it since.

[Oitsujosh]

This is the link from my run though last year. Moral of that story was take the advice of some of the more knowlable veterans here and not over diagnose things to quickly. Lol!
viewtopic.php?f=1&t=81566

[TWC]

Thanx for all the advices...going to follow them as soon as the temperatures here are dropping to a more acceptable level again (we had some not so appealing 36°C yesterday...).

I'm also toying with the idea of looking after a V70 R I had found in the ads, but I'm still waiting for a message by the owner.