ME7 Idle; solved = better braking, improved economy

[SaffronC70]

Hi peeps

Thought I would share my findings

Just for history; I have had a bad idle since I have had the car, fluctuating +/- 100 rpm, occasional hesitation and stalling. The car has had 3 ETMs each resulting in the same idle result.

I have discovered the root cause for this fault: a failed non-return valve on the EVAP system (pollution control).

This was allowing a direct air leak at idle from the inlet piping to the manifold.

Testing involves "sucking and seeing" lol; remove the pipe from the inlet tube and you should be able to suck, but not blow.

To remedy this, I inserted an extra non-return valve (as I am on a budget and didn't fancy paying £48 + vat from Volvo). The OEM valves also acts as a reducer, hence my reason for keeping it.

Results are SOLID IDLE (glourious to me as this has been a pain in 2 years ownership and £££s), better braking power (due to increased manifold vacuum under engine braking) and I have already seen a marked improvement in MPG (I used to see 230 to a tank normal driving. After running the tank dry from half a tank with the fixed leak, I am seeing 260 I'll report back how many miles from a full tank!)

Hope this helps some peeps and it's really quick to check out.

Chris

[Engineer]

Nice one Chris, attention to detail always pays off in the long run.

[scottishvolvo]

Had you also noticed a problem when braking when you had the problem? Could this also affect my S40 2.0T as you symptoms sound similar to what I get occasionally.
Chris

[Engineer]

My 2.0 S40 2001my non turbo has a similar set up so worth checking out mate.

[SaffronC70]

Originally Posted by scottishvolvo

Had you also noticed a problem when braking when you had the problem? Could this also affect my S40 2.0T as you symptoms sound similar to what I get occasionally.
Chris

Yes, occasionally overlight and no real confidence approaching bends in gear; when the idle had a fit of idle hiccups, I could feel the brake pedal soften a lot; this is when the lightbuld lit up in my head (traffic is good for something I guess!)

Chris

[scottishvolvo]

Where did you get the extra non return and where does it go?
Thanks for the info.
Chris

[SaffronC70]

Hi there

Luckily I had a suitable one at home. I've visited several autofactors and non were ANY help, lol.

I reckon they can be bought from Volvo reasonably - the parts guy I had was totally useless.

I have also seen some on EBay that would work.

Chris