The vehicle had been experiencing a light throttle misfire at speeds from 40mph
up to 70mph and a replacement Pressure Transducer appeared to have fixed the
However over the next 1000 miles or so the problem reappeared - I am
not convinced that it was actually cured by the replacement transducer now.
As it was only occurring on very light throttle and especially with the
Cruise Control set and the engine was missing badly I was certain that it
had to be the EGR system that was playing up. I also setup
my laptop using the OBD2 Cable and set it monitoring the
EGR Solenoid with an audio alert telling me when the EGR valve was opening -
sure enough every time the EGR valve opened I was feeling the misfire. I
therefore started working my way through each component and it was whilst I was
checking the EGR valve that I found the culprit.
The EGR Valve on the 24V Cosworth is mounted at the rear of the engine
underneath the driver side inlet manifold and is difficult to see - I had waited
for the engine to go cold (important!!) and then used my hands to feel around
the valve - what I discovered was that the pipe that connects the exhaust
manifold to the EGR valve was very loose. This resulted in an air leak allowing
oxygen to enter the EGR valve which was sucked into the inlet manifold weakening
the mixture. As the EGR only operated under light throttle that was when I felt
The pipe uses plumbing style olives and unions and so the next job is to
strip it all down and see what can be done. In the meantime I disconnected the
electrical plug from the Pressure Transducer to disable the EGR function and the
car was back to it's normal smooth self.
Update: I found a better way of disabling the EGR system by removing the pipe
from the top of the EGR valve and plugging it. This seems better than
disconnecting the transducer.
Test Method: By connecting a long pipe to the EGR valve you can suck on it to
create a vacuum which opens the EGR valve. Doing this whilst the engine is
running will detect any air leaks as the engine will stutter and the leak will
Read the details of the repair.