VW T4 – Going the extra mile to diagnose and repair a fault

Volkswagen T4 – Solving the mystery misfire problem

This T4came in with a misfire. 2 previous garages had taken a look but the fault remained. This vehicle also had a gas conversion to add to the complications, but it ran fine on gas no misfire.

Once we figured out which cylinder the misfire was on we checked for a pulse at this injector with a node light and found no pulse, so the chances were the injector was ok, not worth taking out for testing at this point.

With the correct wiring diagram we did continuity test between injector and ecu and found none. But the odd thing was we had no continuity between any of the injectors and the ecu. There was nothing on the original wiring diagrams about any component in between so we assumed the gas conversion had something installed that cut the pulse to the injectors whilst on gas. So the loom was stripped back and traced to see where it lead

Eventually we found a module in the circuit, seen here on the left of the picture. We then checked for continuity from this module to the injector and to the ecu all was ok.

As the make of this module could not be identified we linked out the module on this cylinder and disabled the gas system which the customer said he didn’t use anyway. Van was now running perfect.

To find out more about how we can help go to our dedicated page for Engine Misfires