Throttle response
I have a problem with a Vauxhall Vivaro 1.9 van which is fitted with a Renault diesel engine. Before I owned the van, it had been diagnosed as having low fuel pressure. It starts up with a smooth idle at around 900rpm, then drops to a really lumpy tickover that hardly registers on the rev counter and doesn’t respond to the accelerator pedal.
I have replaced the high-pressure fuel pump, checked the EGR valve and replaced a couple of glow plugs, but still have the fault. I’m now thinking it might be a faulty injector or am I missing something obvious? I have ordered a fault code reader but it hasn’t arrived yet. Geoff Cross
You do not mention the year of your Vivaro, but given that it has the 1.9 engine, I am assuming it is 2001-2007. The two most likely possibilities are a fault with the engine control module (ECM) or an injector. These vans did suffer issues with throttle potentiometer problem, but this would normally only account for a lack of response, not rough-running. Hopefully when you receive your fault code reader, it may help pinpoint the cause.
In the meantime, I would carry out an injector leak test to see if the injectors are at fault. This is carried out by removing the leak-off pipes on the injectors and replacing them with a piece of tubing which is long enough to place into a pot or jar. The tube from each injector should be placed into a separate receptacle, to catch any fuel that will run out during the test. Block off the return pipe and crank the engine for around 60 seconds – if the engine starts, it can be allowed to run for a short time. The test should show if one or more of the injectors is allowing an excessive amount of fuel to bypass the injector. If the fuel in one or more of the pots is greater than the rest, this indicates a problem with the injector. When an injector fails in this way, it allows the line pressure to become too low, preventing the injection system from operating correctly.
It’s also worth inspecting the connecting plugs on the ECU, ensuring the terminals are clean and have no signs of corrosion.