Sharan stuck on limp home mode

[sde]

I have a sharan, 2.0 litre automatic petrol, on a 1996 'P' plate. I have had it for over four years with no trouble at all. It has done 78,000 miles. Two weeks ago just as I took off from traffic lights it lost all power and stalled. It restarted but would stall if I gave it any gas. My mechanic put it on the computer and it showed that the throttle body was the culprit. The thottle body was replaced but the problem did not go away. The computer however did not indicate any fault. In quick succession the following were then changed or checked

1. The crankshaft sensor was changed
2. The ignition coil was checked
3. The rotary arm was changed
4. The airmass sensor checked
5. The relay(number 30) was checked
6. The distributor head and leads were changed
7. The wiring was checked
8. The distributor was checked

The problem has still not gone. What happens now is that the car will drive without a probleM untill the engine has heated up (after about 4 miles) and will than stall, but will restart with no problem save it will then only drive in limp home mode.

My mechanic is at his wits end. I have looked at all previous posts on this subject on this forum but see nothing that we have not already tried. My mechanic now thinks it may be the catalytic convertor. I am not sure.
Does anybody have any ideas. Any comments will be greatly appriciated.

[Mr.T.]

Had a similar fault with my 2001 diesel, which seems to have just gone away!

When I had the fault I could clear it by pulling over, turning off the ignition, then re-starting the car.

Have you tried this?

[Crasher]

I can't see it being the cat. First of all I would replace the number 30 relay; it is no good just checking it. The VW part number is 165 906 381 and is £11.08 from VW. Are there are fault codes currently stored? Where did the throttle body come from? Did he adapt the throttle body to the ECU in Basic Adjustment mode 04? Did he clear the learnt values from the ECU?

[sde]

Had a similar fault with my 2001 diesel, which seems to have just gone away!

When I had the fault I could clear it by pulling over, turning off the ignition, then re-starting the car.

Have you tried this?

Mr T. Many thanks for your comment. When the car loses power it stalls. It does restart but will drive in the limp home mode. It continues to do that unless you leave it for a while so that the engine is cold again when after a few miles of faultless operation the whole cycle repeats itself.
SDE

[sde]

I can't see it being the cat. First of all I would replace the number 30 relay; it is no good just checking it. The VW part number is 165 906 381 and is £11.08 from VW. Are there are fault codes currently stored? Where did the throttle body come from? Did he adapt the throttle body to the ECU in Basic Adjustment mode 04? Did he clear the learnt values from the ECU?

Crasher - thank you for your comments. I will do as you suggest re the number 30 relay. As for the throttle body I bought it online from a scrap merchant based in Oldham. I note what you say about adapting the throttle body and clearing the learnt values from the ECU. I suspect that was not done. I will get that arranged and let you know how we get on. Many thanks.

[Crasher]

It would not surprise me if the replacement TB wasn't filthy inside, a good clean, learnt value erase and re-adapt sorts most of them out. The TB it isn't a common failure on an ADY, people replace them for no reason most of the time.