What causes low revs and poor idle when cold?
Check the stored fault codes and the live engine parameters. If nothing suspicious, then it can be the fuel filter, dirt in the throttle body or dephaser control valve. The latter two options may be related to the use of the “minimum specification” oil. See the manual for the full algorithm of fault finding (in our Links section).
Why does my engine rev up when idle?
If gunge builds up on the butterfly valve, it can restrict the air required for a smooth idle when the butterfly is closed, so the engine ECU needs to open the Idle Air Valve more that it thinks it should have to and you get into a cycle of surging revs.
Why does my RPM drop when sitting idle at traffic lights?
While I’m sitting idle at traffic lights I put the car into neutral. The engine stays idling at about 1000 RPM. However every now and then it drops down to about 500 RPM and then quickly back up to about 1200 then goes slowly down to 1000 and stays there for a bit until I go again or it drops again.
What happens when engine RPM drops below 800?
However, when the engine RPM drops below the normal range of 800 RPM (for most cars), it is more than likely that you are dealing with an IAC valve problem. In cases where this valve is clogged or is failing, your vehicle will stall instead of slowing to an idle after the release of the throttle.
When to let the revs drop at idle?
You can hear this when driving, lift off but leave it in gear at around 3000rpm and let the revs drop – as it drops below 1500rpm you’ll hear the exhaust note change/start “popping”.
How often does engine RPM drop when idle?
The engine stays idling at about 1000 RPM. However every now and then it drops down to about 500 RPM and then quickly back up to about 1200 then goes slowly down to 1000 and stays there for a bit until I go again or it drops again. It only happens for a second or two and about 3 times a minute.
What happens when revs drop below 1500rpm?
If you lift off the throttle while in gear over 1500rpm then yes, the ecu will not fire the injectors at all. However, as the revs fall below 1500rpm the ecu will start firing the injectors again.
Why does my car Rev by itself when idle?
It sounds like you may have a dirty or failing idle air control valve. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle.