1996 kia mentor rough until warm

[oli]

My father-in-law has a kia mentor that's suddenly seems to drop the revs when idling and stall if not given some throttle. Once the temperature gauge starts to move it idles nice and smooth. It also smells a bit petroly at the exhaust - not massively so, but a bit uncatalysed if you know what I mean.

I'm not very familiar with them and I'm afraid I don't think it's been serviced since goodness knows when ?

I've stayed a bit clear as someone else is looking at it, but I'm thinking temp sensor as it seems to cure itself so quick once up to temperature. It seems to have a very odd throttle stepper motor/idle control that seems to be adjusted by loosening the screws and actually rotating the whole unit. Could that just need adjusting?

I've heard a few things being mentioned, including O2 sensor, clogged air filter and spark plugs, but I can't think these would cure themselves at temperature.

Penny for your thoughts...

Oli

[oli]

Oops meant to add this: is it possible to test a temp sensor with a standard digital multimeter, rather than a scope or similar?

Oli

[chippie]

Try with your multimeter on the Ohms range, the value should change (up or down depending on its coefficient) as it is heated.....alternatively you could replace it with a10 k pot and see the effect that has as you adjust it...Just wire to the slider connection and one of the outer terminals....(maplins about £2-00).

I checked all the temp sensors on a Corsa this way to eliminate them.

[oli]

That's an interesting idea, I'll give it a go it sply testing the resistance doesn't work.

Oli

[Deleted]

Trying to pictue it ,if the thing is on the end of the throttle spindle its the throttle position sensor , these should have a heated idle control valve on the throttle body itself , i would look at base engine condition first if its as you say no servicing , could be cylinder problems ..

[Rhubarb]

As Mac says, back to basics.

Check condition of spark plugs, air filter, oil first

[Dragon]

As Mac and Rhubarb have said, do the basic's first, but air flow meters are fairly common for making them run rough when cold normally they have no idle until warm, original one could come close to writing the car off, mega money but about £50 of the old bay.

[oli]

It's one of those slightly frustrating situations where you get asked for advice but aren't really in a position to work on it properly.

I'm slightly surprised it hasn't thrown up an engine check light. Does anyone know if there is a procedure for interrogating them? (Press accelerator X times etc.?)

Oli

[oli]

Well I've got my hands dirty today!

After Halfords supplying the wrong Lambda sensor initially but then getting the right one within a few hours (and still half the price of my local factors, so fair play) I've swooped it and things are running loads better!

Still a little hunting when idling, but no stalling.

It's had a service as well, but I couldn't get my hands on an air filter today, so hopefully that's for tomorrow.

After pulling my hair out trying to find any info for this engine, especially wiring diagrams for the sensors so I can test them, I had a breakthrough when I realised it's actually the same engine as used in the MX5/miata 1.6 (why do car makers have to use different names in different countries, it makes things so complicated!)

Father in law now happy he can keep his kia, mother in law less happy as she was hoping for a new one...

Oli