M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: keflaman on November 15, 2008, 05:09:35 AM
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Hi Everyone,
Perusing through several of the "idle" related threads I realized many of you are frustrated by an inability or difficulty to diagnose intake leaks or plugged exhaust systems. A helpful solution can be found on the internet by searching for "vacuum gauge diagnostics" or something similar to that.
Here are two websites I found that I think are particularly useful:
http://autospeed.com/cms/A_2393/article.html
http://www.classic-car-magazine.co.uk/articles/fault-diagnostics-vacuum-gauge.html
I decided to try several ways of checking the health of my engine and compare the procedures against each other.
1.Compression check.
2. Leakdown test.
3. Vacuum gauge.
4. Exhaust gas analyzer (EGA).
Every one of the procedures indicated ring bypass, but by far the quickest, easiest, cleanest and cheapest method was using the vacuum gauge. It would also provide a logical starting point for the next step in troubleshooting.
I found at idle the vacuum draw was about 18in (45cm) and would slowly drop one inch and then creep back up to 18 every minute or so. It did this on both the vehicles (318is/190Tkm and 316ti/90Tkm) I experimented on this morning.
HTH.