Idling issues - VW Caravelle 2.5l Petrol

[Simon VW]

Hi All,

I have just registered with VW Watercooled but have been browsing the forums for a while. I am hoping to find a resolution to my idling issue with my 1999 Caravelle 2.5l Petrol.

I believe there has always been an issue with the idling since I bought it nearly 2 years ago however we are now experiencing stalling when setting off from traffic, roundabouts and junctions etc. This happens more often when the air conditioning is on and in hotter temperatures. The revs are around between 8500 and 9500 RPM after starting the van with no air conditioning however the needle still fluctuates and drops and recovers and this is also evident through the engine noise.

As soon as the air con is switched on, the revs drop to just below 5000 RPM and stay there. Accelerating at this point is a very slow squeeze of the accelerator or turn the air con off. Anything more than that and the engine will stall, it's also worth noting that to start the ending again needs a tap on the accelerator at the same time as turning the ignition.

Work so far has included several trips to mechanics who have been unable to diagnose the exact problem - however i now have a new air flow meter, HT leads, Catalytic converter (could be a separate issue)and hours spent researching the issue. My local mechanic has also increased the idling speed manually which I'm concerned about as that may affect the computer readings etc.?

After reading through these forums I have narrowed it down to either the O2 sensor, a Hall Effect sensor or the ECU Relay. I'm open to any other suggestions with explanations preferably. If it is agreed that it could be one of these 3 then how do I look to test if any of them or faulty (and save me hours of mechanics/auto electricians time looking at the wrong thing!)

There is also only 1 of the fans working under the bonnet - it seems to carry on for a long time after the engine has been turned off and is noisy. Could this be affecting the cooling in the engine bay?

Any advice is welcomed - summer is on its way here in Oz and that air con is kind of needed!!

Thanks

Simon

[Seano]

The non working fan is the one that is supposed to come on with the fan or air con. That needs fixing.

As for the idling...by golly that some serious revs you have there. I know sod all about the petrol engines in the T4 but I think your research is sending you in the right direction. Tried asking at the vwt4 forum in the UK?

[neil]

I think maybe you have added an extra 0 to the rev ranges stated.
I will check with my brothers T4 2.5 petrol tomorrow what its running at.

[Simon VW]

The non working fan is the one that is supposed to come on with the fan or air con. That needs fixing.

As for the idling...by golly that some serious revs you have there. I know sod all about the petrol engines in the T4 but I think your research is sending you in the right direction. Tried asking at the vwt4 forum in the UK?

Thanks Seano - yes sorry got a bit excited with the zero's on the RPM. So sitting between 850 and 900 RPM and then dropping to 500 RPM with the air con on.

[Simon VW]

Thanks Neil, yep too many zeros! Thanks for that.

[neil]

sorry for not getting back sooner.

Checked out brothers , it idles on the bar below the 1000rpm bar so 850 sounds about right , turned on air and it only dropped about 50rpm
didn't make much difference.

His biggest issues has been the quality of fuel , having to use the 98 over others otherwise it gets the rattle/pinging, loss of power.

[Simon VW]

Thanks Neil,

Sort of good news anyway - I ended up with a flat battery (left the interior light on!) after recharging the battery the revs seemed to be fine - just below 1000 and only dropping a few with the air con on - some feedback from another forum was that the ECU resets itself with the throttle body sensor and may have sorted itself out. They suggested cleaning the throttle body and resetting the ECU again. Still getting that judder though when trying to accelerate or go up hills. You mentioned the fuel? We did put in 91 last week and it does seem to make it worse??? Thanks for that - i'll fill up with 98 next week.

Cheers

[Sunny43.5]

I agree with Neil use either 95 as minimum RON or for best results 98 RON , the trouble here in Australia is that you cannot trust fuel companies to have their fuel actually match the stated RON . 91 causes my 2.0 petrol T5 to ping and be lousy on power even though it states 91 as the minimum allowed goes to show that 91 is below par .

[neil]

I agree with Neil use either 95 as minimum RON or for best results 98 RON , the trouble here in Australia is that you cannot trust fuel companies to have their fuel actually match the stated RON . 91 causes my 2.0 petrol T5 to ping and be lousy on power even though it states 91 as the minimum allowed goes to show that 91 is below par .

Brother fueled up at New woolies using 95 and has caused heaps of issues , pinging , death rattle , no power on hills , would not change down gears on hills so started to over heat , fuel up again at new woolies using 98 and within 10 minutes van was purring , all pinging and rattle
had gone and temp back to normal on hills , so would this be causing a preignition ???

[Simon VW]

ok that sounds like a major factor . It's running shocking at the moment and just below half a tank left. I'll run through a tank full of 98 and fingers crossed. Thanks for looking in to that.

[Simon VW]

The difference in using RON 98 petrol was amazing - it runs so much better. There is still a knock/judder on acceleration sometimes especially in hot weather. Also the air con sometimes flashes for a while before coming on - a bit of reading online says that there could be a fault with the air con but it only happens occasionally - any ideas?

[Sunny43.5]

Has the tank of fuel been used as if mixed with the 91 it will take awhile for the full effect to take place , also remember up here in Qld our heat can have a bearing as well .

[Greg Simmo]

G'day, I've got a 2003 T4 petrol with the same issue, poor idle no power.
I found myself after spending thousands with so called specialists that my plugs had never been changed and a couple of my coils were knackered. Once I changed those and switched to 98 octane the van runs like a dream with no idle or lack of power issues.
The only drama I have is it shuts down in hot weather with the air con on, my display also flashes occasionally but haven't worked that one out yet.



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[paulypal]

Quirkee.
Check the vacuum hose from the engine to the ECU if leaking can cause many of the problems you mention

[PeterT4]

I had some of the same issues mentioned in this thread, & found a simple adjustment to the distributor cap set things right. The cap just needed to be turned slightly & centered. No more stuttering & missing issues. Might be worth a try.