Revs ''hunt'' on tickover, sometimes revs drop so low car cuts out

The place to start is probably the transmission. One of the telltales of a transmission failure in the making is a problem with your engine's revs. It the revs seem to go up but your Hyundai doesn't seem to be going anywhere it is pointing to a problem with slipping clutch packs or bands. If it is dropping revs on the low end and hunting it may mean that the speed sensor is failing or that the torque converter is having a problem providing a constant pressure. Either way, the place to start is the transmission.

If engine is increasing/decreasing constantly this is called hunting. Or does it suddenly just rev wildly then go back to normal?Please give more detail and resubmit. Please andd make model year and engine option of vehicle

CHECK THE TEMPERATURE AND OXYGEN SENSOR

I had a similar issue while driving the car at about 70 - 90km/h. I also had horrendous vibrations. It ended up being the original trans fluid requiring changing to a more superior product than what they originally came out with. The car had done less than 50000km.

First ensure that the throttle interior is really clean, a surface layer of grime can upset the ECU's ability to meter and govern the air entering the engine. If the throttle body interior is found to be really oily and dirty check on the idle air control valve and make sure that it too is cleaned up. Next put the ignition switch in position 2 (on, but no start) and depress the accelerator fully and release. If there is an issue with the throttle position sensor this procedure can help the ECU relocate the throttle plate position. Start the engine and if it is still hunting locate the air mass meter (AMM) on the air ducting immediately next to the air filter and disconnect the electrical connection. Does this remove the hunting aspect?... the rev speed might change but for the moment concentrate on the evenness of the tick-over. If the idle is even when the AMM is disconnected but hunts when connected then look at replacing your AMM. Try spraying the AMM with no residue electrical cleaning spray to see if this improves matters.

You have described a concern where as the idle air control valve has fialed or there is a vacuum leak in the PCV hose causing a lean condition.

This is most probaly a sticky trottle control whitch need to be replaced and then updated with new software.
Dealers are aware of this trouble, but most offen denies the fact if you ask.
Costs--- 200euro, three years ago!
Volvo owner in Sweden

change battery ,if it starts with jump leads battery flat or altenator not charging

check your catalytic converter

Hi there!

A few more things to check for you.-

A vacuum leak in any of the vacuum hoses will cause the ECU to make random guesses at what's going on.

Have you replaced plugs recently - or at all? This is probably the main cause - and certainly worth a try.

Fuel filter should be replaced at recommended intervals - about 3 years.

Clean your leads and HT gear really well with a degreasant. Any losses will be more noticable at tickover than high revs.

Lastly.........wear on cam lobes or timing belt.

Hope it's cheap for you!
Please spare a moment to rate as fixya! if any of this information proves useful. Thanks (I don't get paid for this)