'Coughing'

[Angie]

Intermittent faults are a bind, and the garage has so far failed to identify this one. Sometimes the engine sort-of 'coughs' as if it's about to cut out, then goes on normally, sometimes for many miles before doing it again. Also sometimes when starting away the engine almost dies but picks up once it's revved a bit. It never completely cuts out,but the idle can go down to about 400rpm for a few moments then back to normal.

I had a new MAF meter last year, and an idle valve. The mechanic thought the idle valve could be faulty so on his advice I put the old one back again, but still the same problem. When I rev the engine from idle there's a strong smell of petrol. The mechanic tested the temperature sensor and that is working. The fuel filter was replaced about 20,000 miles ago - manual says replace at 24,000 but they're going to put a new one on in a day or two just in case, though it seems unlikely that it's the cause.

Oddly after filling up fuel the other day the car ran superbly, so I thought it could be the in-tank pump. Then it started playing up again only a day or two later, still with over half a tank of fuel. After the next fill-up there was no improvement.

It seems worse after driving slowly for a few miles in heavy traffic, and quite disconcerting starting at junctions because I'm never quite sure that it isn't almost going to die.

Any ideas? I noticed on another thread something about a flap in the air-cleaner but I don't know if my car, 1992 Torslanda 2ltr, has that but if so is it likely to be the cause of the problem?

[Clifford Pope]

Is it the model with a fuel pressure regulator at the front of the injector rail?

Pull off the rubber pipe to the inlet manifold and sniff for petrol - a leakage through the diaphram causes petrol to be sucked into the engine.

[Angie]

Originally Posted by Clifford Pope

Is it the model with a fuel pressure regulator at the front of the injector rail?

Pull off the rubber pipe to the inlet manifold and sniff for petrol - a leakage through the diaphram causes petrol to be sucked into the engine.

Thanks, Clifford, I'm not sure but I'll have a look. Petrol being sucked in seems possible, especially as, and I forgot to mention, it's much worse in hot weather, which I suppose, from what my dad told me all those years ago, suggests a rich mixture. On cold mornings it bursts into life and idles smoothly, in the hot it starts easily but the idle is terrible.

[heckflosse]

It can't hurt to read the codes using the OBD thingy on the strut tower.
It does sound like a fuel pressure fault though.
Good hunting!
Jim

[honestjoe]

I wonder could it be drawing air into the system somewhere?..I know..i"m a simple soul..hope you get it sorted..hj.

[Angie]

The mechanic thought about it drawing air which is why he suggested the idle valve could be the problem, for some reason momentarily allowing extra air, but re-fitting the old valve hasn't made any difference so that seems more or less to eliminate that idea. I suppose both valves could be faulty but fairly unlikely.

I took the little pipe off the pressure valve and there wasn't any significant petrol smell. If it stops raining before dark I might check the fault codes but they did that at the garage and there wasn't anything relevant, just the one, 2-3-1, I think, which has been there ever since I had the car and which has never been explained. Doesn't have any relevance to this fault though because it's only developed recently.

I had a look at the flap in the air cleaner and can't see how that could have such a dramatic effect because whichever position it's in there will be air entering. The flap moved freely anyway, if that means anything.

I'm hoping a new fuel filter might help but words of wisdom in the meantime gratefully received! Thanks for the replies so far, you really are a helpful crowd on here.

[stephend]

The flap in the air filter intake is simply to draw in warm air from around the exhaust manifold for cold running conditions, and cold air from outside (makes for more efficient burn) once the engine has warmed up.

When you say it moves freely, you don't mean it's actually loose / detached? I had this on a Sierra once, but the problem it led to was carburettor icing... Thinking about it, icing could lead to rich running - but I've not heard of icing being a problem with fuel injected cars...

[Angie]

Would that be butter icing, royal icing, glace maybe? Sorry, got carried away there!

The flap is in place and held in the 'cold' position by a spring. Not sure about the thermostat of course but presumably it's working correctly and moving the flap to where it should be. I can't think that a malfunction there would cause the problem but people who know about such matters might think otherwise. Have to have a brisk drive up the A30 tomorrow so I hope it behaves itself, though it does seem quite a bit happier when cruising at a steady speed on main roads.

[Clifford Pope]

So it's probably not the pressure regulator.
I'd look at the regular suspects;

Fuel pump fuses 4 and 6
Fuel pump relay (temporarily join 4 to 6 to bypass the relay to test)
Ignition Amplifier on the LH inner wing just in front of the battery
Crank Position Sensor

Plus the obvious - spark plugs, HT leads, rotor arm, distributor cap.

[owner 1948]

had the same problem with my se revs hunting up and down when wating at lights engine almost cutting out some times no problem then another day lots of trouble seemed to go away when used another brand of fuel but came back had it in garage a couple of times with no anwser found then talking to a guy at the volvo meet in warwick county park he had the same problem some time back and used injector cleaner and it went away so i tryed the same and heypresto its gone no problem since for 18 months
hope this helps best of luck with it