Normally, we are told to fill AC systems by weight. That is normally because pressures change greatly depending on temperature. These seldom seen AC pressure charts allow us to directly cross check and test our systems for optimal performance.    
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There are numerous OEM E30 spring part numbers, and the below is the breakdown of what net effect each will have on ride height and how they interrelate with what options you may add or subtract in your E30.  
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E30 Factory manual pinout and illustration showing the routing of the central locking system found on E30’s:    
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This is an excerpt from the factory E30 repair manual instructing how to mechanically and electrically test the ICV (idle control valve) for an M20 engine.
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These CNC ICV elbows replaces your stock ICV elbow. The original elbow is press fit from factory and loosens over time. Once loose, you end up getting a vacuum leak and up until these there was no great way to solve the problem. Most people either try a glob of JB weld or silicone;...
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https://bmw-grouparchiv.de/research/search/searchResult.xhtml;jsessionid=68fb38be4c67d72c9d41bbadf2bf.1
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Directly from the factory repair manual:
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In the world of alternators the one used on most all E30’s is quite simple and straight forward. The Bosch alternators are a a two post design, with D+ and B+ terminals. B+ (also called 30) is the larger of the two and routes through the starter, then the battery junction box and finally...
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If you’re anything like me, before jumping into a job, or while ordering parts, you want to refresh your memory by looking at the area you are going to be working on. Problem is, with an E30, getting clear pictures of the underbody or stripped back engine bay or interior is fairly difficult. Luckily...
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Near most idle issues are derived from unmetered air entering the intake past the AFM (Airflow Meter). Simplified, it means you have a hole in one of your connections, gasket matting surfaces or intake related hoses. Un-metered air is a fancy way of saying that you have additional air entering your system that the...
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