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Jesus · Joined: 05 Nov 2002 Posts: 225 Location: Québec, Canada

I have a strange problem: when the engine is cold, the idle work perfectly, but when its hot, then the malfunction rise. As a exemple, if I run at 2000rpm and put it on neutral, the engine stay at 2000rpm, but if i use the engine for braking and put on neutral at 800rpm, it go up at its normal idle speed of 1100 rpm. So, it go up but dont go down.

Also, when I start the engine and begin driving, when I acc. for the first time, the idle speed fall near stalling for a couple of second then it go up as it should do. The problem only rise the first and second acc. the it disapear.
What could it be?
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Et la lumière fut...

Lizard · Posted: Tue Jul 22, 2003 12:01 pm Post subject:

try disconnecting the mass air flow sensor and try running it.
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3 928s,

Paul · Posted: Tue Jul 22, 2003 12:48 pm Post subject:

As per the shop manual, always check the grounds under the heater valve before doing anything else. BTDT.

ProudGecko · Joined: 26 Nov 2002 Posts: 129 Location: Indiana

I have a similar problem, when the car is cold it has almost no power it seems. The car will as you said almost stall as you accelerate. I also had a problem where the engine would not drop down the RPM's at idle. For me it was just something stupid, the throttle linkage cable needed to be loosened so in effect the gas was pushed down slightly even when my foot was off the pedal.
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1988 Porsche 924S
1986 Kawasaki Concurs ZG1000
1984 Mercedes 190D
1973 Honda CB500

Jesus · Joined: 05 Nov 2002 Posts: 225 Location: Québec, Canada

I think I have put my finger on the problem,

As the problem appear only when the engine's hot, it could not be the sensor. For the cable trottle, its all fine. But still, the trottle must have to do something with it.

Here my hypothesis: Maybe its the trottle that does not close completly for unknown reason. That would explain the trouble when I start it up. And after the engine is hot, maybe the thing expend because of the heat and let pass more air, that would be the explaination for the idle problem.

When I got some time, I shall see the bottom of it.
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Et la lumière fut...

Jesus · Joined: 05 Nov 2002 Posts: 225 Location: Québec, Canada

It Work! although I feel somewhat stupid.
When I was working on the throttle, I saw the small screw adjustement on it. I screw it a little and now, everything work perfectly. At least my hypothesis was okay and no need for new parts.
I set the idle speed at 900rpm, is it good for this motor?
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Et la lumière fut...