oliwb
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| posted on 27/2/06 at 03:55 PM |
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Off Topic (Merc 500SL)
Hi guys...wow my first post in this section and its not even about a locost! Anyway, my dad own a Mercedes 500SL G-reg, with the big V8 in...every
time you put it into park the engine races, prob sits about 1,200 - 1,400 rpm (at a guess) compared to normal idle speed when sat with the brake pedal
on in drive...think it does the same in Neutral but not 100% sure....anyway it did this a couple of years ago and the solution according to Mercedes
was new ECU which they fitted....(I can only imagine how much that cost!) Anyway its started doing it again and I think its the lambda sensor (not
very good at this EFI stuff!) or some other sensor thats gone rather than the whole ECU unit....was just wondering/hoping someone could shed some
light on this.....its also just had a new exhaust last month if that makes any difference and I don't know exactly what they replaced last time
the ECU was done eg dunno if original sensors are still being used....my theory is that one of the sensors is telling it that its cold when in Park
for some reason and its fueling rich (as in choke) to compensate for temp/air/something.....Anyhow thanks in advance....don't need to say how
many beers it would equate to if we don't have to have whole ECU replaced....lots given labour charges and german bits!!! Cheers Oli.
If your not living life on the edge you're taking up too much room!
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britishtrident
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| posted on 27/2/06 at 05:23 PM |
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I don't think the engine is being speeded up when put into to neutral -- i suspect the reverse ie the throttle by-pass isn't being closed
to slow it down when out into neutral-- it is normal for an autotransmision to put quite a bit of load on the engine when in neutral which has to be
compensated for or the engine will stall when put in D or R.
Although there is no way for DIY plug-in diagnostics and it will be down to checking individual components istr the 500SL of that vintage has Bosch
KE Jetronic injection a fairly simple system which gives you hope of getting help outside the dealer network.
It is a hybrid mechanical-electronic system really just an improved version of the older K Jetronic but with control by electronics -- really quite
a simple system.
My first suspect would be the the Auxiliary-air device which is a valve that by-passes the throttle to control the idle speed -- try cleaning it with
carb cleaner. These URLs should help.
http://www.auto-solve.com/mech_inj.htm#MFI12
http://www.boschautoparts.co.uk/pcPetr11_2.html
http://covintechnical.pwp.blueyonder.co.uk/tech_2.htm
http://www.ilexa.co.uk/forum/index.php
[Edited on 27/2/06 by britishtrident]
[Edited on 27/2/06 by britishtrident]
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oliwb
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| posted on 27/2/06 at 05:41 PM |
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Wow great starting point thanks! Oli.
If your not living life on the edge you're taking up too much room!
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jimmyjoebob
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| posted on 27/2/06 at 06:05 PM |
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Following from trident's reply above, try checking the idle control solenoid. This normally gums up with carbon gunge deposits.
Clean it out with carburettor cleaner - this solved the same problem as you are having on a sierra v6 2.9 I had. Very embarrassing when waiting at a
road junction with engine screaming away on its own!
If at first you don't succeed, hide all evidence you ever tried!
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