I have a year 2000 5.7 GSI which will not hold it's revs, even in nuetral.
If I throttle up to any setting, ie 2000 revs, the engine will run at this for about 5 seconds then drop back to near stalling, then recover to 2000 revs for 5 seconds then drop back to near stall etc. in a continuous loop.
This started happening after my local engineer replaced the injectors, because of minor problem with a slight loss of a power over the last few years.
As a result of this new problem I asked him to replace the original injectors, but this new problem remained.
Fortunately my cousin has the same engine in his boat (although 1999) & has let me try swapping parts to help diagnose the problem. Here's a list of parts I've tried changing, without solving the problem:
The whole carb body, including injectors, fuel pressure regulator, TP sensor, IAC valve.
The ECU, Ignition Controll module & MAP sensor.
I've also tested fuel pressure & although the low pressure pump seems high at 11 PSI, the high pressure pump is 31 PSI which i believe is in spec.
Both readings fluctuated by only about 0.5 PSI at different revs & under load.
I've also done a compression test & a spark test & checked electrical continuity of wiring between the various sensors & the ECU connectors.
Something I've noticed is that if i disconnect the MAP sensor, the revs do not surge as above, however there is reduced power when under load.
Any suggestions would be most appreciated.
If I throttle up to any setting, ie 2000 revs, the engine will run at this for about 5 seconds then drop back to near stalling, then recover to 2000 revs for 5 seconds then drop back to near stall etc. in a continuous loop.
This started happening after my local engineer replaced the injectors, because of minor problem with a slight loss of a power over the last few years.
As a result of this new problem I asked him to replace the original injectors, but this new problem remained.
Fortunately my cousin has the same engine in his boat (although 1999) & has let me try swapping parts to help diagnose the problem. Here's a list of parts I've tried changing, without solving the problem:
The whole carb body, including injectors, fuel pressure regulator, TP sensor, IAC valve.
The ECU, Ignition Controll module & MAP sensor.
I've also tested fuel pressure & although the low pressure pump seems high at 11 PSI, the high pressure pump is 31 PSI which i believe is in spec.
Both readings fluctuated by only about 0.5 PSI at different revs & under load.
I've also done a compression test & a spark test & checked electrical continuity of wiring between the various sensors & the ECU connectors.
Something I've noticed is that if i disconnect the MAP sensor, the revs do not surge as above, however there is reduced power when under load.
Any suggestions would be most appreciated.
