2.5l Petrol T4 Idling Issue

[freddo__1]

G'day All, i have just acquired a nice '94 T4 Caravelle, 2.5l Petrol Manual. It's all in pretty good nic, and drives very well. However it suffers from stalling at idle. It was idling at somewhere between 500 and 700 rpm, however after an hour or so of rooting around in the engine bay (and being angered by the fact the post '93 models have no idle adjustment) discovered that there's a microswitch on the throttle (which isn't in the workshop manual) which it appears tells the ECU the throtlle is closed, because after adjusting it's bracket so that it was 'switched' when the throttle was closed, the idle speed went up to the 750 - 800 rpm mark where it should be. It also starts without the use of the throttle now too.

However! I also discovered that the Idle stabilisation valve is not operating, apparently it should be buzzing when at idle all the time. I removed the valve and checked that it wasn't seized, and it buzzed like crazy when hooked up to 12 volts. I then checked the voltage across the plug with the motor idling, and there's nothing coming out... i checked the positive wire to earth on the chassis and there's 0.5 volts. I found someone on "howtomendit.com" appears to have exactly the same problem, but nobody has provided an answer...

It's not so much of a problem now that i've fixed the microswitch thing, but when you turn the A/C on, 90% of the time it stalls, and a short stab at the throttle often has the same result.

Apologies for the newbie essay, any help would be much appreciated.

[kiwi mike]

I have been doing reading... shock.... Poor oxygen sensor may be having effect also? Just tracking what to do with mine. If in doubt replace I read. Else it makes mix heavy uses excessive fuel also. Just idea to sideways pursue.

[phaeton]

Welcome to VWwA Freddo & Mike

[majimbo]

Hi there, do you have any pics of the throttle switch ur referring to? and how did u adjust it? Thanx

[20vkitcar]

try replacing the 30 power relay at the fuse box cheers steve

[majimbo]

Hi, yes the 30 Relay also known as the ECU Relay does make a difference. Maybe theres oil in ur ECU on the Map sensor? I had a similar problem and that was it. might want to have it checked and replaced if its too far or just cleaned if its not that bad. Let us know how u go, Laters

[majimbo]

Hi, might also be ur idle stabiliser, just guessing

[robs wedge]

I have a similar problem to yours, How did it end up? Did you have the map sensor cleaned? was it the relay? Cheers! Rob

[robs wedge]

I just popped the top off the ECU relay to have a squiz. I ran a meter over it and the 'make' contact 87 seemed to have an inconsistent resistance. Voila! It had a dry joint onto the little circuit board. It is re-soldered, I checked other solder joints, re doing a few and re-installed the relay. HUGE difference so far (fingers crossed) ... Rob

[DVR68U]

thats good to hear.
cheers brenton