Rough Idle on LPG fine on Petrol!

[wrichardson1999]

Hi Guys, hopefully you can help...

I've a E200 (auto) on an 'L' Reg that I've had for about the last 5 years, I bought the car on around 95k and had the car converted to LPG. The car has now done around 240k but has started to develop problems!

The car is fine on acceleration/normal driving, although when I slow down (crawl) or stop the revs drop through the floor then jump about, if I stop car either stalls or idles on very low revs.

What I've done:

Drained the heavy end from the lpg, cleaned lpg diaphram
Changed Plugs
Changed oil and filter
Air Filter

The plugs were supplied with a .8mm gap setting which apparently is the correct gap size BUT the plugs that were fitted by my garage were .89? The car wouldn't even start on .8 but when adjusted to .89 it at least starts and ticks over...

The car only stalls when hot!

Help

Anyone?

What should I change next?

Should I? can I change the engines idle speed?


Many thanks



Wayne

 

[996jimbo]

You will find that someone else has had problems with LPG on another enquiry.

I had my previous car converted to LPG and that quickly developed a rough idle on gas but not petrol. This was down to worn HT leads, and replacing the HT leads cured the problem. The problem shows itself on gas only as it needs a stronger spark.

If you run the engine in a darkened place you may be able to see whether there is any shorting through the insulation of the HT leads.

Only stalling when hot may suggest a different problem, or be because the mixture is weakened as the engine warms up and therefore still be due to a weak spark...

Best of luck!

 

[wrichardson1999]

Thanks Jimbo,

Yea I've already looked through and tried everything else before it starts to cost lol

I've taken a look and it doesn't seem to have a normal dizzy cap and rotar arm or HT leads as I'd expected? I guess I can't just pop in to Halfords for them?

 

[996jimbo]

Not a bl**dy clue my friend!

Having said that, you can always buy them individually; pluck off one end from a plug and from whatever is on the other end - measure it and replace it then carry on round.

Avoid doing my clever trick of taking them all off and then spending 2 hours with a torch, large spanner and long screwdriver trying to work out which order they go back in!

 

[MW]

I don't know about the 220, but some years ago I lost patience with a spark plug lead (Which are tight) and pulled it off with the end cap on my 1992 230E! Very silly I know. Anyway Halfords wanted a fortune, but Euro Car Parts did a complete 5 lead set of German quality for £30+. Very good quality too. A recent distributor cap and rotor arm was £20 all in. I replace these at 60k anyway as good practice. I agree if you do replace them do so with one lead at a time, and grease the distributor cap holding screws with copper paste grease as they can get very stiff and rusted in.
If you spend £50 and replace the lot, it might work, or if not replacement will eliminate the problem and is good policy anyway. Are the leads 240k original. If so they have done well.
What has been your general experience of LPG. What does it do to MPG? Any disadvantages?

 

[wrichardson1999]

Thanks for the replies guys,

I went down this route last weekend, I'd ordered a new dizzy and rotar arm from my local motor factors to find that under the bonnet I don't have one? this model use's a coil pack that's apparently dealer only? is this true?

Up until now everything has been ok, I've only a 74 ltr tank which I can get 62ish ltrs into (only fill to 80%). Costs around £19 and get just under 300 as a rule a little more sometimes.... No real loss in power, well worth the cost of the conversion if you travel often and far? works around 100 mile round trip so provides good savings over petrol.

Cheers


Wayne

 

[Oxmerc]

more on idling and lpg

You may not have seen the thread I started on this:
http://forums.mercedesclub.org.uk/showthread.php?t=10875

It seems to be a common problem, with several possible remedies

 

[wrichardson1999]

Thanks, yes I'd noticed the thread trying to find an answer last week... still no luck though...

Did replacing the HT leads and clean the flap in the throttle body work? and has it resolved your problem now?

A local merc parts supplier I use (around 60% cheaper that stealership) are closed due to holidays so hopefully get a price for a coil pack early next week.

Thanks for the pointer...

Anyone any other advise on this?

Cheers guys

 

[Oxmerc]

next week

The car will be going in on Tuesday next week for the work to be done, so I'll report back after that.

Fergus

 

[wrichardson1999]

Cracked it!

I managed to source some non dealer ignition leads over the weekend, installed and now running perfect, can't remember the last time it ran this smooth....

have noticed, that the original leads can simply have the cables replaced, the plugs simply screw onto the cable, MB quote only £28 to replace each cable, much cheaper than the £240 to replace complete leads!!!.... I ended up getting 3rd party for £21+VAT! as MB said I'd have to wait until Tuesday for the replacment leads...

Anyways

Thanks for you help everyone....