BMW 520I E28 M20 idle problem

Hi everybody!
I have some trouble with the engine..At 286.000km the main gasket blew and I got a "new" engine in. After that a lot of trouble started:
1) The idle speed is 1500 rpm (warm, autochoke inaktive) - the idle screw put in zero position. The idle speed on the old engine was 800-900 rpm.
2) The engine lacks power below 2500 rpm. This result in "humping" when I shift from 1. gear to 2.gear. The only way to avoid this is to run the engine upto 4500 rpm and the shift.
What could this be ? There does not seem to be any vacume leaks. The valvs are ticking a bit. Could it be the fule mixture ?
Best regards, Uffe Nielsen
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You might have missed installing a sensor, or reconnecting a cable or earth-lead somewhere. A vacuum leak or bad seal would explain the idle problem, and might explain the lack of power. If you clean the engine up so it shines you can often spot a vacuum leak by the filth that soon accumulates around it. Might also be a valve stem seal.
Steve

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Hi Uffe,
I would first check the throttle position switch to make sure it is working properly. Usually a high idle like you explain can be traced to a misadjusted or inoperative idle switch. Second I would make sure the timing belt is installed correctly and that the valve timing is correct. Third you might want to check your AFM to see if it has some dead spots.
It easy to do and I can help you through this.
Blake
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I owned years ago BMW 520i and also had this first problem. Reason was a defective auxliary air valve. This is a valve which gives extra air when engine is started, and the should close when cooling water gets hotter.
M20 engine is well known of its behavious of not having torque in low rpm. Of course there can be a real fault like vacuum leaks which are common.
Petri

I
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Do you know the part number? if you don’t, where can I obtain the number? I have the same problem and in my country no one know the part or no appear in the part charters.
Thanks
"Petri Haapanen" wrote:

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