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Engine Low Idle Problem

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Dodi Hendra
Posts: 3

Engine Low Idle Problem

Post#1 » Mon Jul 13, 2009 5:28 am

Hello,

I just purchased 280 G 1989,
Need your suggestion related to problem I faced with my 280 G, Couple days ago I travel nearly 800 km but on the return trip I found idle engine Rpm drop to 600 rpm and suddently if I release the pedal engine off if AC on.

The next day, I start engine in the morning, like usual the RPM increase until 1200 rpm automatically for 10 minutes and later on drop down to around 600 rpm again.

My question :
Is it normal in the morning Engine RPM increase until 1200 Rpm ?
Any Idea why the RPM drop to 600 Rpm.. is it normal ?

Thank you in advance

Best regards

Dodi Hendra

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Dai C
Posts: 786

Re: Engine Low Idle Problem

Post#2 » Mon Jul 13, 2009 6:58 am

Welcome to the group. I can't help you being a diesel guy but I'm sure you will get a response from someone that knows your motor.

-Dai

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Indiana Drew
Posts: 233
Contact:

Re: Engine Low Idle Problem

Post#3 » Mon Jul 13, 2009 7:41 am

In my 1980 280 with the AC on, I idle at about 700 and with the AC off at about 1000. I don't have the vacuum compensator installed so that the idle is automatically increased when the AC (compressor) is turned on. Is your AC from the factory?

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Indiana Drew
Posts: 233
Contact:

Re: Engine Low Idle Problem

Post#4 » Mon Jul 13, 2009 7:59 am

Here is a photo:

Image

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stevegsmith
Posts: 2666

Re: Engine Low Idle Problem

Post#5 » Mon Jul 13, 2009 8:28 am

Drew,
That takes the cake as this month's best post reply.
Nicely done.

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Indiana Drew
Posts: 233
Contact:

Re: Engine Low Idle Problem

Post#6 » Mon Jul 13, 2009 8:45 am

stevegsmith wrote:Drew,
That takes the cake as this month's best post reply.
Nicely done.

Steve - thanks, but that drawing is not my work (credit to Mike, Desertstar, if I recall)- I just asked a similar question on P3 some time ago. Until we know how this truck is equipped, I may have made matters worse. Its been a year and I still have not got it figured out on mine. As a 1980 and a truck that came over under the 25 year rule, it has the European(read non EPA) setup. Most of that stuff pictured is not on my M110 ... At least I remembered where I had seen the diagram ...

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syncro_G
Posts: 824

Re: Engine Low Idle Problem

Post#7 » Mon Jul 13, 2009 9:24 am

wow, I hadn't seen that image before.
those hoses are really hard to see.
I pulled my engine out a few weeks ago and had my first real look at them.
one of those larger (about 3/4" dia) hoses has a crack around one end.

In the last year, several members with early to mid '80's 280GE trucks have problems with these hoses.
hose lifespans seem to be at their end after 25 years and the resulting failures are frustrating to diagnose.

but having said that, an idle problem isn't necessarily an indication that this is the problem.
the first step should be to check for vacuum leaks.

-C

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stevegsmith
Posts: 2666

Re: Engine Low Idle Problem

Post#8 » Mon Jul 13, 2009 10:36 am

Indiana Drew wrote:
stevegsmith wrote:Drew,
That takes the cake as this month's best post reply.
Nicely done.

Steve - thanks, but that drawing is not my work (credit to Mike, Desertstar, if I recall)- I just asked a similar question on P3 some time ago. Until we know how this truck is equipped, I may have made matters worse. Its been a year and I still have not got it figured out on mine. As a 1980 and a truck that came over under the 25 year rule, it has the European(read non EPA) setup. Most of that stuff pictured is not on my M110 ... At least I remembered where I had seen the diagram ...

Drew,
Your award for this month's best post reply has been rescinded.
Nice job though on your resourcefulness.

Mike, Since this info was second generation and no doubt you've already received plenty of praise, the only thing you get is a second hug from me next time we hang. Lucky you huh?!
;)

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DesertStar
Posts: 2184

Re: Engine Low Idle Problem

Post#9 » Mon Jul 13, 2009 10:47 am

Dodi, yes high idle at 1200 or so when cold is normal and should drop down to 750-850 rpm. There is an idle adjustment screw (plastic off-white colored) that will raise or lower the idle rpms. This must be done/adjusted at engine oil temp of 60-80 degree celcius and not when too hot like after a drive. I attached image to show you the adjustment screw. I would first try turning your idle up and see if that solves the problem....it may, but I would not be surprised if some of the vac and air lines under the intake manifold may need some attention. By the way, it is easy to check for a vacuum leak on those lines below the intake manifold, just spray a small bit of WD40 or carb cleaner and see if your idle goes up.
Let us know what you find...there are some very informative threads around that we can steer you towards....besides my G had the same issue as yours, which was not easily solved by just adjusting the idle, as I found I had major vacuum leakage under the manifold which for me resulted in a complete rebuild of the idle air ductwork and vacuum system.
Mike
Attachments
idle.JPG

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Indiana Drew
Posts: 233
Contact:

Re: Engine Low Idle Problem

Post#10 » Mon Jul 13, 2009 12:10 pm

stevegsmith wrote:
Indiana Drew wrote:
stevegsmith wrote:Drew,
That takes the cake as this month's best post reply.
Nicely done.

Steve - thanks, but that drawing is not my work (credit to Mike, Desertstar, if I recall)- I just asked a similar question on P3 some time ago. Until we know how this truck is equipped, I may have made matters worse. Its been a year and I still have not got it figured out on mine. As a 1980 and a truck that came over under the 25 year rule, it has the European(read non EPA) setup. Most of that stuff pictured is not on my M110 ... At least I remembered where I had seen the diagram ...

Drew,
Your award for this month's best post reply has been rescinded.
Nice job though on your resourcefulness.

Mike, Since this info was second generation and no doubt you've already received plenty of praise, the only thing you get is a second hug from me next time we hang. Lucky you huh?!
;)


And I thought I'd get the smart a$$ of the month for bad joke on my Muffin Crawl reply ...

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