'Loping' tickover and lurching.....

[Hal M]

Hello. I've joined for some tech assistance.

 

I live in France, French wife, dog, and 19 year old daughter (she's not French but sounds like she is, as she's been here since she was 18 months old)

 

In 2002 I aquired a 2000 reg Suby Outback 2.5.

 

I didn't actually BUY it....In a fit of madness, I swapped a beautiful restored 1964 Alfa-Romeo Guilia Spider with Bertone hard-top for the Suby plus £1000. (The Alfa is now worth 25,000 euros +)

 

At the time, I reckoned the Suby was worth more, and fully intended to get shot of it immediately, but it didn't sell, and we've run it as a work horse ever since. We had it converted to LPG or GPL as it's known here.

 

It's done a biggish mileage in the time we've had it, over 120,000 in 8 years, currently it's on 245,000km.

 

We've replaced the clutch once, rebuilt the gearbox once, belts, plugs, discs, nothing unusual, plus fitting a Frantz bypass oil filter, and recently I decided it needed some tidying, as someone in a 4x4 ran up the backend in Feb 2009, so I've just replaced the rear bumper plastic.

 

At the same time I repaired and painted the front one, as my wife had left the car without applying the handbrake and it ran into a pile of rocks.....

 

It's had a stupid problem for some time, we reckon it started about 3 years back....

 

I don't think this is an LPG related problem as it's exactly the same when it's running on petrol.

 

It seems to start up ok, and initially the tickover is ok, then after the initial short period, (under a minute) after starting cold, the tickover gets rough and 'loping', as though it's running on 3 cylinders, and the car rocks and feels very un-smooth.

 

We have checked, and this doesn't seem to be a problem of one cylinder dropping out, as my mechanic friend tried removing each plug lead, one by one, and he thinks this isn't the problem.

 

If I move off from cold, it will seem very lacking in power and will normally stall, and be difficult to start, after less than 1km if I have to stop at an intersection.....this always happens from cold, and it seems to need to be revved to 3 or 4k once it re-starts, in order to drag itself across the main road to the other side.

 

After about 2km there's a long hill, and the car is by this time still not very warm, and has very little pulling power up the hill.

 

Once properly warmed up, it seems to run better, and is always happier at higher revs. It will not pull smoothly in a high gear at small throttle opening, it tends to 'buck' and lurch....needs to be dropped a gear to run cleanly. It will, once hot, sometimes drop to tickover normally, (though still with the lumpy, 'loping' tickover) but often will simply 'drop to zero' and stall, often in the worst possible place such as while crossing an intersection, or, as recently, a busy roundabout in Grasse.

 

On a light throttle, if I try to drive in a higher gear, it will 'buck' and is clearly unhappy on small throttle openings, so I have to drop a gear to stay in the higher rev range...

 

We tested the air valve (not sure what this is in English!) but the thing on the left side of the inlet plenum which is controlled by the ECU and regulates air going to the plenum...cost over 300 euros, and though the original was testing as if it was dead, this has made no noticeable difference to the problem.

 

We also changed the air filter which was dirty, the plugs having been changed last summer.

 

Next will be the front lambda, as this clearly is past its change date anyway.....but it's a puzzle, as it seems to have only 2 wires.

 

The ones I've seen illustrated on the web seem to normally have 4.

 

I can't see what make it is without removing it, and I'd rather have a new one before taking the car off the road AGAIN....it's been in the garage for 2 months recently anyway, partly for this problem, but also as it needed a new rear bumper plastic due to a 4x4 attack last year in the February snow.

 

I have now ordered the oxygen sensor and new Bosche plug leads, from http://www.allsubparts.com which seems to offer very good value.

 

They quote 30 US dollars, for the lambda, while the French Subaru concession wants $330 equivalent!!!!!

[johnceggleston]

i assume tickover means ''idle'', what does ''lambda'' mean?

 

do you have a CEL, check engine light, on?

 

does it run differently when it is hot than it does when it is cold?

[Olnick]

"Lambda" is the O2 sensor, n'est-ce pas?

[Fairtax4me]

Lambda or Lambda-sonde is an oxygen sensor.

 

If it does this when the engine is cold the O2 sensor is not the culprit, although it probably won't hurt to replace it at 245k km.

 

I think you have... A vacuum leak. There should be a diagram on the bottom side of the hood detailing the vacuum hose routing for the engine. Follow all of those hoses (there are only a handful) and make sure each one is connected securely, free of cracks, splits, and general dry-rot.

 

Did this problem start immediately after the LPG conversion?

[Hal M]

Lambda or Lambda-sonde is an oxygen sensor.

 

If it does this when the engine is cold the O2 sensor is not the culprit, although it probably won't hurt to replace it at 245k km.

 

I think you have... A vacuum leak. There should be a diagram on the bottom side of the hood detailing the vacuum hose routing for the engine. Follow all of those hoses (there are only a handful) and make sure each one is connected securely, free of cracks, splits, and general dry-rot.

 

Did this problem start immediately after the LPG conversion?

 

No....there was a period of several years when it was fine, as far as I recall it was summer 2007. The gas was done in 2003 or early 2004.

 

I'll check for vacuum leaks.......

 

Lambda seems to be the English term....but I may be wrong there, I've lived here nearly 20 years and do sometimes get things wrong.

 

I do a lot of work with Lotus cars and that's what we always call them. The O² sensor or Lambda on the Elise is something which seems to have a short service life.

 

If I spent a fraction of the time and effort on the Sub as I do on Lotus and Caterhams, the poor thing would never have got into such a state in the first place!

Edited January 6, 2011 by Hal M

[Fairtax4me]

No....there was a period of several years when it was fine, as far as I recall it was summer 2007. The gas was done in 2003 or early 2004.

OK. That might rule out anything having to do with the LPG system... maybe.

 

On a side note? Can you take some pictures of the LPG setup under the hood? I have a long standing goal of one day converting my carburetted truck to run Propane or LPG.

 

If there is any part of that system connected to the intake manifold or intake pipe/airbox, maybe give that a wiggle and make sure it's on there tight as well. I don't recall if that year has a MAF sensor, but if there is any air entering the intake box after the MAF sensor it will throw off the ECUs air density calculations, and that can cause it to run rough.

[Hal M]

I'll take some pix.

The GPL tank is where the spare wheel should be, holds about 60 litres.

My wife (she's French!!!) actually drove off after refilling one day with the gas hose still locked on.....it did bend the body panel a bit, and apparently the hose has an emergency snap-off connector, otherwise she would have uprooted the pump.....so glad I wasn't there!