I bought this at a garage sale last month to replace my VW rabbit diesel pickup, however, am having problems since I drove it home and hoping for help. The vehicle sat in a back yard for 1+ year without being driven, however, I was able to start and drive it home. I filled the fuel tank that was near empty with ultra unleaded and added fuel additive/cleaner. I have consulted numerous forums and read through many threads- but nothing seems to help with this so I am posting this now.

The Issues:
On cold startup (after sitting all night), the idle is low to normal. When warm it is around 700 rpm and I can drive and drive and it will resume normal idle, however, if I shut the engine off and then restart- the idle goes above 2300 rpm at idle and does not change whether I shut the engine off and restart or pull the IAC plug out. If I pull the plug off the MAF, the idle drops for a moment and then returns to high idle.

Attempted Solution 1:
I cleaned out the intake manifold, butterfly valve, IAC and the MAF, including trying a new IAC. I lubed the throttle body linkages that move as they should. Fixed all the potential vacuum leaks with new hoses and gaskets and sprayed plenty of carb cleaner everywhere afterward with no noticeable change in RPM. Here are the numbers as provided by an Ultragauge (UltraGauge OBDII Scan tool & Information Center) when the vehicle is warm (in closed loop circuit).

Results 1:
Idle: 2365 RPM
Intake temp: 111 F
Timing Advance: 50
Throttle position (ABS TP1%): 12.5
Engine temp: 169 F (this seems about as it should and not cause a high idle)
MA: 0.17 g/s
CAT Bank 1 Sensor 1: 8789 (Ultragauge indicates this is very high (normal is 2011 max) and gives and error, although the Disco has no codes and no check engine light).

Attempted Solution 2:
I replaced both Bank 1 O2 sensors with new (waiting for a better tool to arrive to get Bank 2 and replace those also)

Results 2:
The idle and other readings are not significantly changed (a few rpm difference or a few units from the CAT) from Results 1.

This morning on startup (cold) it was at high idle and while still cold the Ultragauge indicated it was in closed loop.

Potentials Solutions:
There is no one that I can find within a 5 hour radius of my location in Lubbock, TX where there is a Testbook for an ECU reset.

What should I do?

 

Check to see if you have a thermostat installed. A stock D1 should run about 195-205F, an alternate 180F stat that I use will run about 178-183F. I tested mine with no stat and it was running about 150. There are two heat sensors near the thermostat. Single wire runs the gauge. Square top one runs the ECU and the numbers you see on the scanner.

Base tps% on mine is more like 9%, may be a little there. When I bought mine it would high idle, could not resolve it battery cables off, shorted for 30 minutes, finally replaced ECU from boneyard, $30. Got lucky, because usually you have to replace ECU and the green alarm control module as a matched set, about $100 from some of our dismantlers.

People have been posting about a new diagnostics tool in the under $150 range, I wonder if it can reset ECU values.

Ooops - saw you said D2. I thought the year for D1/D2 was 1999. Thermostat will certainly be different, but still should be warmer.

 

Yes, that should have been Disco 1. How likely is it that a 10 degree F temp off of normal cause such a large increase in RPM? If TP is high isn't that just another indication that the idle is also high?

So I may need to search for an ECU? Could a Testbook tell if the ECU was bad?