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ponkokanada
Member
Date registered: Nov 2010
Location: Halifax Nova Scotia, Canada
Vehicle(s): 1976 240d, 1991 190e 3.0 manual, 1984 280ge
Posts: 5
| Help: 280GE high idle
Hey everyone
I recently aquired a 1984 280GE LWB automatic. The truck starts fine warm or cold and has good power (at least it seems ok for an Automatic) but the idle speed when in park is around 1300RPM. When shifted to Drive the idle drops to around 800 RPM or so. The idle speed doesn't change at all even after truck warms up, and the exhaust smells a pretty rich all the time. Not sure about the fuel consumption yet as I literally only put 100kms on it so far.
I noticed that the wiring around the engine is in poor shape, when I got it all of the wires were broken off the sensors/switches on the left side of cylinder head. So far I managed to find the wire to get the temp gauge working but that's all. Also the Vacuum thermo valve for EGR is broken off and is missing one of the vacuum lines. I tested the warm up compensator by unplugging the vacuum line going to it and found no difference in how the engine ran. I also unplugged the cold start injector which also made no difference with the engine hot or cold.
At this point I can't completely gut the vacuum wiring of the truck to troubleshoot because of the cold weather and fact I need to drive it frequently. I'd like to try and do some basic tests to lower the idle as the tired automatic transmission does not seem happy being shifted to drive when the engine idles fast.
1. Is there such thing as Idle adjustment through the air butterfly valve on the m110 or is it purely done by the fuel distributor?
2. Would a simple vacuum leak cause fast idle? I could measure the vacuum level to see if I have a leak if I knew what the proper pressure is for given RPM.
3. I'm assuming the K-Jetronic adjusts for temperature with the warm up compensator...would a faulty compensator increase idle speed?
4. How does the warm up compensator sense the temperature with external sensor and if so where is it?
5. Could someone provide me with wiring and vacuum diagrams of for the engine. 1984 280GE vin: 460 2331 7035 380 |
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hipine
Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
| RE: Help: 280GE high idle
ponkokanada - 1/15/2013 7:25 PM
1. Is there such thing as Idle adjustment through the air butterfly valve on the m110 or is it purely done by the fuel distributor?
2. Would a simple vacuum leak cause fast idle? I could measure the vacuum level to see if I have a leak if I knew what the proper pressure is for given RPM.
3. I'm assuming the K-Jetronic adjusts for temperature with the warm up compensator...would a faulty compensator increase idle speed?
4. How does the warm up compensator sense the temperature with external sensor and if so where is it?
5. Could someone provide me with wiring and vacuum diagrams of for the engine. 1984 280GE vin: 460 2331 7035 380
1- Yes, there's a big-ish flat blade screwdriver plug near the throttle body that adjusts idle air bypassing the throttle plate for idle (NOT a stop screw for the lever or butterfly)
2- Yes, leak causes fast idle, but just measuring vac won't tell if its a leak or other cause
3- Yes, bad WUC effects idle speed. WUC is diagnosed via fuel pressure tests
4- WUC senses temp via proximity to the block and internal bimetal strip and electric heater coil, no sensor
5- You need more than that. Manuals are available from http://4x4abc.com/Mercedes-Benz.G-Class.manuals/engines.html but also elsewhere on the web
See also tech articles at Hans Hehl's web page and clubgwagen.com and search the archives more here. Bram has a GREAT thread on going through the idle air supply system. In my opinion your problem is most likely in the maze of rubber hoses and valves under the intake manifold. You'll need the patience of a saint to go through it and thank heaven Bram's been there before.
Good Luck!
-Dave G. |
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oskar
Elite Veteran
Date registered: Sep 2006
Location: Lyons, CO
Vehicle(s): 1981 280GE, 2002 G500, 280SE 4.5, Audi A4 1.8T
Posts: 708
| RE: Help: 280GE high idle
My bet is that a prev owner has "adjusted" idle with mixture adjusting screw of the airflow sensor flap. Compensation for a fault WUR, aux air valve or most likely a vacuum leak . ( Cracked rubber hoses)
I would checkt the hoses first, if they feel somehow hard .. just replace then.
Oskar |
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hipine
Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
| RE: Help: 280GE high idle
oskar - 1/16/2013 6:59 AM
My bet is that a prev owner has "adjusted" idle with mixture adjusting screw of the airflow sensor flap. Compensation for a fault WUR, aux air valve or most likely a vacuum leak . ( Cracked rubber hoses)
I would checkt the hoses first, if they feel somehow hard .. just replace then.
Oskar
I totally agree with you Oskar. There are so many things that can go wrong and ways to compensate this system without reaching root cause that I hate to even recommend a place to start. I feel like the real best thing is what friends of mine at work call a "global reset" of the system back to known good conditions. I agree that the place to start when doing that on a near 30 year old system that depends heavily on rubber pipes and valves, is to just replace the lot out of hand. Its expensive and difficult, especially on the M110, but once done, and then adjustments like idle mixture, idle speed, ignition timing and valve lash are set, the truck's performance will put a smile on the face for another 30 years to come! A correctly running M110 really is a thing of joy and beauty.
Its been a month or more since I talked to Sean at Eurotruck. If he's not reading this, I think I'll call and suggest they put together a group of service kits that get a person all the parts they need to refurbish these hose systems. I think part of the issue that they get neglected is that people don't know what they need. I know that I'm lots more likely to tackle a job if I know I have all the parts going in. Like the axle service kits they've put together. I know this one will be more challenging due to the number of variations, but might be doable.
Sorry to go off track a little, but with this subject I think it is important to steer it in this direction a little, based on my own experience and that of others who've posted at length on it. Since I have the head off the m102 I'm sort of in the middle of thinking about this for that engine and should probably write it up as I don't think anyone's treated this subject for that motor as extensively as Bram has for the M110.
Good to hear from you again Oskar.
Try to keep warm up there.
-Dave G.
PS - some good related discussions with pix of the system involved with idle air:
http://www.pointedthree.com/disc/forums/showthread.php?tid=10862&po...
http://www.pointedthree.com/disc/forums/showthread.php?tid=9927&pos...
http://www.pointedthree.com/disc/forums/showthread.php?tid=10712&po...
http://www.pointedthree.com/disc/forums/showthread.php?tid=12197&po...
http://www.pointedthree.com/disc/forums/showthread.php?tid=13276&po...
http://www.pointedthree.com/disc/forums/showthread.php?tid=8455&pos...
http://www.amazon.com/Bosch-Fuel-Injection-Engine-Management/dp/083...
Edited by hipine 1/16/2013 11:55 AM
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oskar
Elite Veteran
Date registered: Sep 2006
Location: Lyons, CO
Vehicle(s): 1981 280GE, 2002 G500, 280SE 4.5, Audi A4 1.8T
Posts: 708
| RE: Help: 280GE high idle
hipine - 1/16/2013 8:30 AM
Try to keep warm up there.
last Saturday we hiked up to the boulder field of Longs Peak.
Approximatly at 12000' and -15 F we turned around ... too cold
Oskar |
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roughneck
Expert
Date registered: Apr 2006
Location: UK, Germany & USA
Vehicle(s): 270 cdi.300 GD 300 GE.lwb 300 GE.swb. Disco 2
Posts: 4398
| RE: Help: 280GE high idle
oskar - 1/16/2013 8:59 AM
My bet is that a prev owner has "adjusted" idle with mixture adjusting screw of the airflow sensor flap. Compensation for a fault WUR, aux air valve or most likely a vacuum leak . ( Cracked rubber hoses)
I would checkt the hoses first, if they feel somehow hard .. just replace then.
Oskar
I second that twice. |
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bram_r
Expert
Date registered: Apr 2007
Location: the Netherlands
Vehicle(s): 1984 MB 280GE, 1982 MB 300GD, 1986 Subaru XT 4WD
Posts: 1659
| Re: Help: 280GE high idle
Thanks for combining all the M110 info Dave.
I read about that schubumluftventil just yet, still nice researching that, made me smile to find it's function eventually even though I know have this diesel in my 280GE now 
Still great forum this! |
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Otiswesty
Administrator
Date registered: Jun 2007
Location: Portland, Oregon
Vehicle(s): 463.241, 461.213
Posts: 3003
| Re: Help: 280GE high idle
I've started going through these threads on K-jet optimization. My idle at cold start is very low bordering on stalling. It has been adjusted by a shop so that it runs better when cold, but will run at too high of an idle once warm, like 1700 RPM. If I temporarily come off the clutch a bit, the idle will drop to a more reasonable level while stopped.
I have a lot of experience with L-jet on my 78 Westfalia and am looking forward to getting the 280GE K-jet sorted as well. I have just purchased all of the attachments from an explanted 280GE motor so I will have some spares to work with and clean and rebuild as necessary. I think the 280GE will be a long time car for me. Unfortunately, I have quite a number of irons in the fire right now and it is hard to give full attention to this as it is running okay overall.
Any obvious pointers on the low cold idle are appreciated
Edited by otiswesty 11/23/2019 1:22 AM
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DUTCH
Administrator Doppelgänger
Date registered: Apr 2006
Location: US, GA, Atlanta
Vehicle(s): 2015 Audi Q7 3.0 TDI,2018 Sprinter
Posts: 9963
| Re: Help: 280GE high idle
That warm up regulator needs a special pressure gauge to set up and adjust. Hipine has one, since he got mine when I sold my 280GE many years ago. |
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DesertStar
Expert
Date registered: Apr 2006
Location: San Diego, CA USA
Vehicle(s): 85-280GE/95-G320/08-G500
Posts: 2156
| RE: Help: 280GE high idle
Years ago when I first bought my 280GE, I tackled my idle issues by starting from scratch...replacing 25 year old rubber on intake. See photos. The one with new rubber is from my G, The other photo is from Bram. There was different configurations pending year, options etc. Mine had additional "air slide" for factory air conditioning. Make sure your rubber air piping is in order and not "jinky" from previous mechanics...I had some issues of altering stock piping and repairing holes with silicon sealant and some cracking. I think once rubber got warm it expanded and let air in adding to weird idle at times.
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hipine
Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
| Re: Help: 280GE high idle
Not sure what, "come off the clutch a little bit" has to do with anything. All idle speeds are checked with the car in neutral.
I'd check the control pressures first because it's WAY easier than chasing vacuum leaks. Make sure control pressures are correct starting from cold, through warm up, and after shut down. Once that's put to bed THEN I'd be on to the various air control items in the system making sure they're working correctly at the prescribed temperatures and load conditions. Then I'd be on to the octopus of air pipes under the manifold. Of course, check all the vacuum fittings and hoses that you can easily access on top of the motor at any time. Oh, and stay away from whatever shop hacked the cold idle for you. They did more harm than good.
After each work session, use the Gunson Gastester to set the idle speed and CO correctly before doing some test driving.
You'll be rewarded with a GREAT running vehicle for a long time to come. But sadly a lot of them have been hacked on by idiots and don't run right as a result. In my experience, screed up settings are much more common than malfunctioning parts or broken hoses, etc.
Good luck!
-Dave G. |
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