Had oil changed ,injectors cleaned and air filter replaced Now the speedometer reads 30 instead of 0 at idle

Needs a tune up. Adjust engine timing, replace plugs and plug wires, replace air filter, oil and oil filter, fuel filter and clean fuel injectors, adjust valves.

Clean throttle body add fuel injector cleaner good one.change a fuel filter and check an air filter.

Take it back to the mechanic.

it sound like your van is running rich.the use of those products are not going to improve your gas consumption.instead change air filter .clean or replace air mass sensor.check tire pressure .also a bad fuel injector will make the other ones spray more gas in order to keep engine at idle

If you had the ecu read it would probably say egr code. also a number of other codes to do with injectors and co2 sensor. you need to clean out the egr and clean out the air vent pipe from the sump to the top. also clean out the idle valve on the in take. also the breather pipes. you may even need to change the air filter. and when was the fuel filter changed. an oil change a filter change would not go a miss if it has not been done in awhile. routing maintenance will stop this happening again.

Check your Tire Pressure, Change your Air Filter to a K&N, Change your O2 Sensors, Add SEA FOAM to your Fuel and have an INJECTOR CLEANING PROFESSIONALLY DONE

try slightly over filling oil level if engine starts and runs for a minute or two then dies the oil pick up in sump has fallen out (cracked mounting bracket) or sucking air instead of oil. you can remove small tin engine sump after draining to check oil pick ups, after confirming it runs ok for a little while once over filling oil level in engine.
another thing that goes is the rail oil pressure sensor which reads incorrectly and a tell tale sign this is broken is the injector loom connector is full of engine oil when disconnected this is near engine oil level dip stick(wiring loom comming out of rocker cover), the sensors reading can be checked with scan tool before starting with ignition on, (0-0.2MPA) it must read if its reading higher with ignition on only (motor not running) the sensor needs replacing, the engine ECU needs to see approx 200MPA when cranking to get injectors to start to work properly and higher when running at idle and beond (up to about 5MPA at higher revs) if this is not getting to this or readings are fluctuating badly indicating air in oil the injectors wont supply the correct amount of diesel. in which the engine oil comming from low pressure (pickup pump) to then high pressure oil pump to rail and injectors.

when was the car last serviced? if recently serviced what service did the garage do? servicing the car at 20,000 km involves changing spark plugs/ clean or change air filter, fuel filter/ engine oil filter in some case it alson involves cleaning the throttle body and cleaning injectors.depends on your climate and driving condition, your car might be having a faulty airflow meter or faulty idle speed control sensor, have those two checked or cleaned then if problem still the same have your car checked by a code reader to pinpoint the problem.

Check calibration. Muffler supports from the front till the back, there should be proper clearance. Is your diesel fuel of proper cetane rating for the engine? Check your belt drive system, is there any part that is excessively draining engine power, power steering pump, air con compressor, alternator or generator? Do these preliminary steps and isolate.

check both lambda sensors for breaks in wires and for open circuit on heater side of lambda sensor on the one under the car on the second cat,failed heater element will not heat gas engough for sensor to read causing false readings , also check for slow i.a.c valve on inlet manifold.