The purpose of this Esmagamus guide is to enable you to diagnose and hopefully fix idle issues in most petrol engined cars (these hardly ever happen in diesels and being so much simpler than petrol engines, diesel problems are usually easier to pinpoint). Most of us have been hunting for information from various sources while trying to fix a problem we can't even name. A substantial amount of time and money can be saved just by knowing how various systems work together and how specific parts can fail.
We will cover:
-the importance of engine vacuum;
-the difference between not having or having a lambda sensor;
-lean and rich burning conditions;
Once again, the instructions provided will be influenced by the cars I have. Although I may not be familiar with your particular vehicle, the same basic principles and reasoning processes still apply.
Sweat saves blood, blood saves lives and brains save both. - E. Rommel
I add that brains also save time, and time is money. Be smart.
Note: Annexed schematics are available on on RAR format. Download and extract if you can't read the schematics.
Step 1: Occam's razor: number one principle
As an example, last week I found myself stranded on the side of the road, my car had developed a bad misfire. What could it be? An injector? A valve? Then I applied Occam's razor and checked the distributor first: the rotor arm was broken and the carbon button and spring had been dislodged.
Any shop manual on car electrics will state that wiring fails more often than senders or control units. Once again, before thinking "my battery is dead and must be replaced", one should think "are the terminals properly bolted down?".
In his Summa Totius Logicae, i. 12, Ockham cites the principle of economy, Frustra fit per plura quod potest fieri per pauciora [It is futile to do with more things that which can be done with fewer].
—Thorburn, 1918, pp. 352–3; Kneale and Kneale, 1962, p. 243.
Being an abstract subject, I include the following link to those interested: http://en.wikipedia.org/wiki/Occam%27s_razor