Help needed

[Dirty Rooster]

Is the stalling behaviour the same with the air filter removed?

[Gareth2510]

Its doing it no matter what. Today ive had the plugs out gaps are good plugs a bit sooty. I pulled all the injectors cleaned there port swapped the injectors with some cleaner newer ones. Cleaned the amm carefully with cotton bud. Pulled the dizzy cap checked rotor all good. Pulled all boost pipes hoses etc checked all good. Now one thing i have noticed with regard to the dim dip resistor my lights are on constantly but swiched off inside the car. resistor dam hot burned my thumb unpluged it lights go off. Could the resistor be my fault.

[Laird Scooby]

Lights first - Volvos are equipped with Day Running Lights that are on with the ignition. This brings the dim-dip on whenever the ignition is on, regardless of the position of the light switch. It's how they are made, or at least was when yours was made.

What was the plug gap when you measured them? Sooty plugs doesn't tally with the symptoms you're getting of lean running.

What about the carbon brush in the centre of the dizzy cap inside? All present and correct?

[Gareth2510]

Yes side lights are on all the time but im on about mainbeam lights. Plug gaps were around .7... Fuel rail has good pressure when i press the bleed nipple. I might take a fuel sample tomorrow see if it has any water in it. Tried another crank sensor. Nothing is working.

[Gareth2510]

On the dizzy cap do you mean like a little black button in the center of it.

[Laird Scooby]

The dipped beam lights will also come on at reduced brightness when you plug the dim-dip resistor back in - it's how they're meant to work!

If it was main beam it would dazzle oncoming traffic, even in the daytime, hence dim-dip.

Plug gaps sound ok, you've already proved the fuel is ok by pulling the vac hose off the FPR with it idling and the revs increase. That made the mixture richer and the revs increased with it so therefore the mixture must be very lean without doing that.

It's designed so that when that hose is on the FPR, the pressure in the fuel rail is maintained at the correct level for the engine load so somehow, somewhere, extra air is getting into the inlet manifold that shouldn't be.

Find the thick vacuum hose that goes to the brake servo and either crimp it closed as near to the inlet manifold as possible with a pair of Molegrips or remove it from the inlet manifold and block the stub with a piece of tape or a short length of the right size hose with w bolt in the other end. See if that improves matters.

You could also try adding 2L of meths to the fuel tank, i don't think it's water in the fuel from the symptoms but if it is that will help.

Yes, a little black button in the middle, should be about 10mm long and spring loaded.

[Gareth2510]

Huh that would be one hose i havent even considered i will get on to that first thing. Really am at my witts end with this one. Lol will be getting sold if i cant fix it.

[Gareth2510]

Oh and thanks for all your help so far.

[Laird Scooby]

I'm thinking of a faulty non-return valve in the hose or possibly a faulty servo causing a constant air leak into the engine.

It's a shot in the dark but might give some other clues.

Has it got air-con by the way?

[Gareth2510]

No air con. Is there a valve in that hose then because when i get in the car start it and go to drive i can hear a sort of puff of air lasts about 2-3 seconds. Not when pressing the brake peddal though.