I've just about had it.... this car, '02 v40, 98K, for the past 3 years, on occasion, idle rough on hot start, hesitate and not want to go unless floored. Also will start a rough idle and want to stall when sitting in heavy traffic (45+ minutes).

Replaced plugs, wires, coils. Also replaced the fuel press. regulator for long crank times (which solved that problem) and also replaced the thermostat and temp. sensor when those went bad. All parts OEM. Only codes I've ever gotten are for random misfires.

Thought all might be contributing to the idle problem, but it happened in traffic again today.

Volvo and indep. mech. can't find the problem.

Really want to love this car, but seriously thinking about making a change to something made on another continent.

Any ideas before I sent it off a cliff?

 

I wonder if an injector is acting up. Maybe try running fuel injector cleaner through the system.
Also maybe try cleaning the idle motor.

 

both been done in the past trying to solve this....

 

Inspect the hose really good going from the intercooler to the intake manifold.

Also one more thing I can think of that might make it act like that. But I really don't want to make you spend more trying to fix it and it not be it.

In the induction hose going from the air box to the turbo has a valve in it just before the turbo. I have seen them cause alot of problems as well. If they go bad all the way they can blow the fuse in the fuse box and stop the car from running all together.

 

Where are those and what am I looking for?

I should also mention that sometimes when this happens, but not always, I can hear a momentary noise from under the car (i think towards the rear) when I give it gas. Almost a low whine. The other thing is that when I'm stuck in traffic and it starts acting up, if I give it some steady gas to keep the idle up, the tach will roam up, hold, drop, hold and repeat. As soon as I can get up some speed, all clears up and it runs good again.

I'm feeling pretty lost at this point.

 

The hose is about the size of a normal heater hose. It is like under where the top intercooler hose attaches from the throttle body to the intercooler.

Maybe like a fuel pump whine like when a pump goes bad?

 

Doesn't sound like a pump kind of noise. Could a clogging, but not clogged cat make a sound like that?

 

Possible but a clogged cat is not common at all. Never seen it on a S40.