kia sedona 2003, cold running problem

[timtheenchanter]

I have a 2003 2.9 CRDI sedona, with an increasingly irritating problem.

When the engine is cold, on tickover, or low revs, the engine appears to be hunting (ie revs dipping buy about 250rpm/returning to normal on a regular pattern)
The problem disappears when the engine warms (or just about, there is sometimes a very slight change in tick-over engine note, that is so small as to not affect the rev counter.)
The last couple of mornings this dipping has been enough for the car to be difficult to start and keep running until the engine has run for a few minutes.

It did a similar thing at the end of the summer last year (with a very slight change in revs), it then seemed to rectify itself, but has now returned worse.

So far, I have only removed the EGR valve and given it a good clean, this seemed to make a slight improvement, but i'm not sure it wasn't psychosomatic but it has now got worse again.
Im tempted to blank off the EGR, even temporarily to see if it improves things.

The EML only comes on when the revs keep dipping for an extended period, the fault then clears itself, and, having had it read, seems to leave no code behind.

sorry for the long post, wanted to get as much info in as poss.

 

[Belle427]

i would have thought it would log a fault code if the management light has come on even for a split second. I would start by inspecting all the engine wiring connections first, i believe these engines use an air intake heater of some description and this may be a good place to start if it is temperature related

 

[timtheenchanter]

I'm sure I replied to this before, never mind...

Well, yesterday she refused to start at all, got the man in a yellow van round, 10 mins of poking around, quick squirt of easy start, she fire up and ran fine.

his diagnosis, as you had suggested, preheat fault.

You are also quite right, it does have an air intake preheater, and NO glowplugs.

I had the heater off last night, one connection decidedly dodgy, will remake later on today. the whole thing was gunked up, so wouldn't have done much for airflow or thermal transmission so cleaned that up.
The resistance on both elements is 0.5ohm, so presuming that these are ok.

tried connecting the heater direct to the battery this morning, via a length of 10mm cable, no joy there, still needed easy start to get going.

Im going to add an extra earth from the heater block to the batt to see if that helps any.

 

[Belle427]

sounds like your getting somewhere, i would expect to see the heater remain on for a couple of minutes but am not 100% sure