G51 NAV
26th February 2010, 17:51
This is a long-standing niggle with MGT #502 which I don’t think is related to its lack of use, but I’m prepared to be told it is. If so, I’ll just have to tolerate it.
From stone cold it starts and runs fine at fast idle (1100-1200rpm ish), but as soon as the needle on the temp-gauge begins to move, it starts to run really lumpy at anything less than 3k because it seems to be too rich. With foot off the pedal it’s so lumpy that the tacho-needle is virtually back to horizontal and the engine nearly stalls, but it never quite does.
Then, as if by magic, when the temp gauge passes ¼, it somehow snaps out of it and runs as smoothly and evenly as you could ever expect, idling at about 850-900rpm and revving cleanly all the way up.
No problems with hot or warm restarts, unless it's sunk back into that 'not quite cold, not quite warm' zone.
I’ve tried a different fuel ECU, a different ignition ECU and I’ve checked for blocked vent pipes.
I once thought I’d solved it because I found a crack in one of the elbow-connectors on the vacuum-pipe from the carb to the ignition ECU.
Could it be something to do with the way the one way valve is connected (pictured below)?
On other MG Turbos I’ve seen, this little device is connected up in every conceivable way, but surely only one way will be right? On the car in question, pipe A goes back to the inlet-manifold (with a metal restrictor in the other end of the pipe), pipe B goes back to the block and pipe C connects to the underside of the air-box.
If it was faulty, or connected up incorrectly, would it give rise to these symptoms?
TIA, from your friendly technical numbskull :D
(Ask me about polishes, sealants and waxes: I can bore any insomniac comatose by talking about those, but what goes on under that bonnet remains witchcraft to me, beyond the very basics of 'suck squeeze bang blow')
EDIT: I bet it's the O-rings!
From stone cold it starts and runs fine at fast idle (1100-1200rpm ish), but as soon as the needle on the temp-gauge begins to move, it starts to run really lumpy at anything less than 3k because it seems to be too rich. With foot off the pedal it’s so lumpy that the tacho-needle is virtually back to horizontal and the engine nearly stalls, but it never quite does.
Then, as if by magic, when the temp gauge passes ¼, it somehow snaps out of it and runs as smoothly and evenly as you could ever expect, idling at about 850-900rpm and revving cleanly all the way up.
No problems with hot or warm restarts, unless it's sunk back into that 'not quite cold, not quite warm' zone.
I’ve tried a different fuel ECU, a different ignition ECU and I’ve checked for blocked vent pipes.
I once thought I’d solved it because I found a crack in one of the elbow-connectors on the vacuum-pipe from the carb to the ignition ECU.
Could it be something to do with the way the one way valve is connected (pictured below)?
On other MG Turbos I’ve seen, this little device is connected up in every conceivable way, but surely only one way will be right? On the car in question, pipe A goes back to the inlet-manifold (with a metal restrictor in the other end of the pipe), pipe B goes back to the block and pipe C connects to the underside of the air-box.
If it was faulty, or connected up incorrectly, would it give rise to these symptoms?
TIA, from your friendly technical numbskull :D
(Ask me about polishes, sealants and waxes: I can bore any insomniac comatose by talking about those, but what goes on under that bonnet remains witchcraft to me, beyond the very basics of 'suck squeeze bang blow')
EDIT: I bet it's the O-rings!