Author Topic: 450SE D-jet idle fluctuating - video of  (Read 2615 times)

13B

  • Vintage
  • ***
  • Posts: 871
  • Location: Bonerland - I like big butts and I cannot lie!
450SE D-jet idle fluctuating - video of
« on: 03 March 2008, 02:21 AM »
Hi people,

I've just uploaded a video of my 450SE's fluctuating idle problem:

http://www.youtube.com/watch?v=9a4WiAk9Ass

Pretty sure I know how to fix the problem (restirctor in the aux air line or replace or service air slide thingy), but just wanted to be sure.

Cold start idle revs up to nearly 2000, then drops back to 1000 instantly, then back up, and down... worse than a 13B rotary engine with full race bridge ports...

I.
450SEL 6.9 #5440 = V MB 690 , 450SE # 43094 = 02010 H , 190E/turbo # 31548 = AOH 68K

oscar

  • W116 Addict
  • ****
  • Posts: 4,043
  • Location: Riverina, NSW, AUSTRALIA
Re: 450SE D-jet idle fluctuating - video of
« Reply #1 on: 03 March 2008, 03:00 AM »
 8)  Mate, that exhaust sounds awsome too.   ;D

The fluctuating - exactly what I had. 

It's not going to cause damage but if it really bugs you, before you do the fixes try screwing the idle screw in during a cold start until the idle stabilises. 

1973 350SE, my first & fave

13B

  • Vintage
  • ***
  • Posts: 871
  • Location: Bonerland - I like big butts and I cannot lie!
Re: 450SE D-jet idle fluctuating - video of
« Reply #2 on: 03 March 2008, 01:22 PM »
LOL - the exhaust system was purely coincidence - we didn't have the car running long enough before I bought it to examine it closely.  Sounds good though.  Just how I like them.

Will examine all setting for things like idle speed and ignition timing before tampering with the aux air system. 

Since a replacement MPS and replacing the fouled plugs has it running now it's my bet that previous owner has fiddled with every setting known to man to try to get the car to run right... now the MPS is right all the other stuff has to be brought back into line.

I.
450SEL 6.9 #5440 = V MB 690 , 450SE # 43094 = 02010 H , 190E/turbo # 31548 = AOH 68K

13B

  • Vintage
  • ***
  • Posts: 871
  • Location: Bonerland - I like big butts and I cannot lie!
Re: 450SE D-jet idle fluctuating - video of
« Reply #3 on: 04 March 2008, 02:56 AM »
Well I've got it running better... did you know if you remove the wire from the temp sensor on the snorkel of the air cleaner the engine stops hunting?

Warm-up fast idle is still too fast - god the valve train is noisy on this sucker!  Bet the PO hasn't adjusted it ever...

Idle screw has no effect whatsoever while warming up.  Suspect I have to change the aux air valve - lucky I have a spare...

When it finally warms up it sounds good, less top-end noise etc.  Still haven't test driven the thing.

Oil pressure is good when fully warm.  Warm or cold start it goes 1st turn of the key. 

Oh and my timing light is dead so I have no idea what the ignition timing is, other than its probably wrong...

More vids soon.
450SEL 6.9 #5440 = V MB 690 , 450SE # 43094 = 02010 H , 190E/turbo # 31548 = AOH 68K

oscar

  • W116 Addict
  • ****
  • Posts: 4,043
  • Location: Riverina, NSW, AUSTRALIA
Re: 450SE D-jet idle fluctuating - video of
« Reply #4 on: 04 March 2008, 03:50 AM »
did you know if you remove the wire from the temp sensor on the snorkel of the air cleaner the engine stops hunting?

Geez I can't remember now what mine did.  I know that plug was not attached when I first got mine.  If the hunting goes because you pulled that plug I'm not sure if the hunting disappears as a direct result, rather it is secondary to the ECU changing the mixture because it's reading the intake temp as something that it's not.  In other words, I think the ECU receiving an open circuit or non signal from that Air Temp sensor assumes warm ambient air equal to or above a preset value.  So the idle mixture isn't rich as it would be for a normal cold start and the idle RPM's are a fraction lower.  Lower then that upper value RPM that triggers the fuel cut off switch. 

That make sense?  I'm wingin' it without my books. ::)

Usually this problem shows up during winter, not warmer month cold starts, but that's assuming everything else is ok.  Mine has done the fluctuating during warmer months too but was all the time during winter.


Quote
Idle screw has no effect whatsoever while warming up.  Suspect I have to change the aux air valve - lucky I have a spare...

I can't believe that.  I mean I believe you but it's not what I expected to hear.  Apart from changing the aux air valve - First check the hose going from the aux air valve to the idle speed control screw assembly {the one with clamps (clamps shouldn't be necessary BTW)} pic below.  Or for any other leaks in the idle air circuit past the idle speed control screw assembly.  The rest should be metal lines that branch into either head, so check the two nuts for tightness where they attach the lines to the plenum.

1973 350SE, my first & fave

Niclas

  • Classic
  • **
  • Posts: 125
  • Location: Close to SAAB, far from proud.
Re: 450SE D-jet idle fluctuating - video of
« Reply #5 on: 06 March 2008, 03:40 AM »
13B,
have you checked the aux valve? Mine was clogged with soot from the crancase ventilation. You can put the copper part of the aux valve in boiling water and see if it closes, othervise clean it with some solvent and do the boiling thing a couple of times and it will close more and more for each time until it's back in busines again.

/Niclas
1975, 450 SEL, Rusty but fantastic.
2005, E 220 Cdi, Just fantastic.
2007, A 150, Just Girlie
1938, 8.5m Cabin Cruiser, absolutely no plastic.