Occasional high idle speed prob... 2.1DJ.

[wasserleaker]

Wondered if anyone has any ideas on this annoying intermittent problem.....
every other day or so, my engine will, when warmed up, suddenly start idling at around 1500rpm instead of it's usual 800-ish rpm, when it does it, the revs will drop to normal very briefly every 5-6 seconds, then back up to 1500rpm again.
i changed the blue 'temp 2' coolant temp sensor for a new genuine one, and checked continuity from the sensors conn. plug to the relevant terminals on the ECU plug which was ok, no change, the throttle closes nicely to the stop every time, and the throttle position switch is set right and checks out with the multimeter, idle stab. unit is only around a year old, new dist. hall sender baseplate at same time, all connections seem uncorroded and sound, any ideas what else to check??
some journeys, it never happens, and ticks over nicely, so i'm a bit puzzled what could be causing it, could it be the dist. vac unit or the air bypass valve?
cheers for any help!

[Aidan]

ps pump load switch ?
aircon clutch ?
injector leak ?
something is either asking the ecu to pick up idle or sufficient fuel and air is being intook to make it idle at that speed or the throttle cable / pedal is sticking ?

[wasserleaker]

Thanks for the reply, Aidan...
the throttle is def closing against its stop screw every time, and cable is freely moving, no tight spots, ordered some inj. seal rings from TPS to hopefully eliminate any air leaks there, will get the multimeter on the powersteering pump switch and wiring between it, and the relevant ECU connector pins, to see if it's working ok, i know there is a bit of wear in the throttle spindle/ thr. housing which could possibly be sucking in air ocasionally, need to open out the holes, re-bush it with 8mm dia bushes at some point, and renew the seals if they're available, got rid of a lot of the play by wrapping 2 turns of 1.5thou shim around the lower end of the spindle! (it's pretty bad !)

[syncroy]

hi, I had a very similar problem a couple of years back & followed the same path, water coolant sensor, ideal speed regulator etc & then came across this article;
http://www.benplace.com/vanagon_intermi ... ndrome.htm" onclick="window.open(this.href);return false;
Basically, the article describes a problem with the Air Flow Meter. Don't be put off as my symtons were not exactly as he describes in the article & were more akin to yours. It involves soldering a tantalum capacitor between terminals 2 & 4 of the air flow meter (this is much easier than it may first sound) I bought a 15 volt 22 microfarrad tantalum capacitor from Maplins which was around £3. The capacitor helps even out the signal therefore keeping the idle constant.

just follow the instructions on the link. The hardest bit is removing the plastic lid from the AFM. My tip is use a scalpel, keep repeatingly scoring away at the seal from the underside. This took quite a bit of time & I ended up getting a small screwdriver to gently help prise it open. After you've done the soldering, clean off any left over sealant & reseal using Solvol clear Instant Gasket. I've got a 2.1 DJ, & after the fix I haven't had any fluctuation out of the idle speed.

if the link doesn't work or if you need any more information let me know

All the best

Roy

[wasserleaker]

That's interesting Roy, sounds worth a go, i did notice today that when the high idle speed occurred, removing the electrical conn. from the air bypass valve made the engine return to it's normal 800rpm idle speed, this is prob a symptom rather than the cause of something 'telling' the ECU to up the revs, as Aidan suggests, if anything it shows the air bypass valve is working ok, does the power steering pump sensor work as an on/off switch? ie, either open circuit or continuity, just wondering how to test it in case it's faulty, as far as i understand, the ecu gets its info from, the coolant temp sensor, and air temp sensor in the airflow meter, and alters ign timing and inj. opening times accordingly, and when the steering pump is sapping engine power on full lock when parking, the sensor gets the ECU to up the idle speed somehow, is the air bypass valve used as well as inj opening duration and ign. timing changes to control idle speed at different loads/temperatures?

[syncroy]

hi, I haven't got power steering on my vehicle so I can't comment on whether that would affect is so drastically. My symptoms were that the van would drive perfect for prolonged periods & then without any consistency the idle would go through the roof............normally when stationary in queuing traffic for maximum effect!!! I would recommend trying the fix on the Air Flow Meter, it won't break the bank & it worked a treat on my van as well as the guys who originally posted it. As I mentioned, I did it 2 years ago & the idle hasn't even fluttered since.

Best of luck & let me know how you get on. SyncRoy