Classic Audi Technical Mech/Tech Engine » MB High Idle

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Old 04-04-20, 08:16 PM   #1
mark turner
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Default MB High Idle

Hi all,

I haven't been on here for years due to other activities and interests. Anyhow my mb has developed a high idle issue that I'm struggling to resolve and could do with some more knowledgeable input.

The car starts fine and idles normally until the engine gets to operating temperature and then the idle increases up to 1.5k, 2k and at its worse 3k.

I initially thought an air leak was the logical culprit, however I have so far not found any. The next thought was the warm up regulator but when I disconnect the electrical plug there is no change.

Any ideas and thanks in advance.
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Old 06-04-20, 08:58 AM   #2
BackintheFold
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Do you mean the warm up regulator (by the side of the block near the spark plugs, fuel)
or
the Digital Idle Stabiliser? (top of the engine near the back by the coil, air)

More likely the DIS. Unplug and see what happens.

It does sound like excess air.

Aloso check the throttle valve is closing properly, not spring gunked up...
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Old 06-04-20, 06:39 PM   #3
mark turner
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Quote:
Originally Posted by BackintheFold View Post
Do you mean the warm up regulator (by the side of the block near the spark plugs, fuel) Correct, no difference when disconnecting the electrical connection.
or
the Digital Idle Stabiliser? (top of the engine near the back by the coil, air)

More likely the DIS. Unplug and see what happens. Already done this and no difference, I even blanked the hose.

It does sound like excess air.

Aloso check the throttle valve is closing properly, not spring gunked up... Yep, throttle valve is fully closed.
I'm going to put my fuel pressure gauge on and check the pressures next followed by pressurising the intake.
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Old 06-04-20, 07:11 PM   #4
Sandro
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To me, it seems excess fuel, not air. Might be wrong.
Excess air should make idle go up and down as "ecu" would try to stabilize it.
The problem could be the fuel pressure regulator or the little sensor at the end of the engine block near the firewall.

Will follow this topic to see what was wrong.
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Old 06-04-20, 07:56 PM   #5
Colin Aitchison
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Hi guys, sorry but might not be much help, the last time I had high idle speed on a k-jetronic injection system, the 12v wiring plug to the warm up regulator had come off and was idling at 2,200 rpm when warmed up, make sure you have a 12v and earth at warm up regulator wiring plug, also ISV are also prone to sticking open, giving high idle speed.
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Old 07-04-20, 11:34 AM   #6
mark turner
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Well, it's not doing it now.

Confused ��
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Old 07-04-20, 04:19 PM   #7
mark turner
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Quote:
Originally Posted by Sandro View Post
To me, it seems excess fuel, not air. Might be wrong.
Excess air should make idle go up and down as "ecu" would try to stabilize it.
The problem could be the fuel pressure regulator or the little sensor at the end of the engine block near the firewall.

Will follow this topic to see what was wrong.
Hi Sandro, for future reference should the issue return, the temp sensor you mention, is that the one that controls the cold start valve?. If so I have disconnected the electrical connector from that and it made no difference.

Regards Mark.
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Old 08-04-20, 08:26 AM   #8
mikes2
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On the MB the temp sender at the rear of the head is for the gauge.

csv is ecu controlled
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Old 08-04-20, 03:11 PM   #9
AdrianH
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I had exactly this problem on my MB, caused by the ISV. I improved matters, but didn't cure them, by soaking the ISV in carb cleaner for a couple of days then flushing it out with more of same (obviously keep the electrical end out of the stuff). Loads of black gunge came out. However, my ISV was too far gone and eventually I (or rather Pete Reeve) managed to get hold of a new original one *problem solved. BTW we'd tried less-expensive after market ISVs (apparently the correct part) but they were not fit for purpose.
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Old 09-04-20, 02:11 PM   #10
BackintheFold
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Does teh MB have a DIS and an ISV ?

LOL, actually, am interested-which is the correct term?
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