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myothercarsanerskine
Joined: 02 Nov 2013
Posts: 3
Location: Worcestershire
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 Posted: Sat Nov 02, 2013 4:05 pm Post subject: Ghost in the maachine |
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| Can anyone explain why the engine on a Series 2 car should suddenly go from tick-over to 3,000rpm with no prompting from the driver? It will do this sometimes when the car is at rest and sometimes when you lift off the accelerator pedal when driving (which can make approaching road junctions interesting). The only way to calm it down is to switch off the ignition, although it sometimes takes two or three attempts. What would cure it (short of exorcism)? |
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Lagondanet
Administrator
Joined: 03 Jan 2007
Posts: 3109
Location: UK
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| Posted: Sat Nov 02, 2013 4:44 pm Post subject: |
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| Which car are we talking about? (VIN)? |
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jonc
Joined: 21 Sep 2010
Posts: 584
Location: Cheshire, UK
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| Posted: Sat Nov 02, 2013 5:19 pm Post subject: |
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Some initial thoughts:
The cruise control bellows have control of the accelerator. Unplug the connector to the bellows to eliminate.
There is pressure control of the distributor's vacuum advance which can advance/retard the ignition by removing or supplying vacuum, or supplying pressure to the vacuum advance diaphragm. There is a microswitch next to the carbs which operates when you take your foot off the accelerator. I am not sure you would get 3,000 rpm from this system malfunctioning though.
Jonathan |
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myothercarsanerskine
Joined: 02 Nov 2013
Posts: 3
Location: Worcestershire
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| Posted: Mon Nov 04, 2013 3:57 pm Post subject: ghostinthemachine |
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Chassis number is 13508
I don't think it's the bellows; there's no movement of the injection rod linkages when the revs rise. In fact, I have now detected a slight "chuff" sound just before the revs rise, which suggests the opening or closing of a vaccuum valve or pipe. And the revs it hits are nearer 4.500 than 3,000rpm. |
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Vincent
Joined: 20 Nov 2007
Posts: 1055
Location: Belgium
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| Posted: Mon Nov 04, 2013 5:36 pm Post subject: Re: ghostinthemachine |
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| myothercarsanerskine wrote: | Chassis number is 13508
I don't think it's the bellows; there's no movement of the injection rod linkages when the revs rise. In fact, I have now detected a slight "chuff" sound just before the revs rise, which suggests the opening or closing of a vaccuum valve or pipe. And the revs it hits are nearer 4.500 than 3,000rpm. |
13508 is an injection S3, and one of the most desirable with the VF dash... I remember this kind of problem on SIERRAS and GRANADA/SCORPIOS EFI from this era. The cause was the Hitachi debitmeter, which we had to replace. On 13508, the two debitmeters are Weber ones. Not sure the replacement is the solution, but you could check them... They are situated on front top end of the alloy air intakes ( 2 screws ).
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myothercarsanerskine
Joined: 02 Nov 2013
Posts: 3
Location: Worcestershire
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| Posted: Mon Nov 04, 2013 5:59 pm Post subject: Ghost in the machine |
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| Thanks for that Vincent. Short of replacing the debit meters, how do I test them? |
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jonc
Joined: 21 Sep 2010
Posts: 584
Location: Cheshire, UK
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| Posted: Mon Nov 04, 2013 9:32 pm Post subject: |
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Ah - EFI - I was assuming carbs.
Check the throttle position sensor and its connections. Have a look at http://www.bigturbo.co.uk/ - the sensors page.
Big and dramatic changes are less likely to be the air and water temp sensors although these are cheap and easy to test.
Vincent - debitmeter is an air flow meter right? The V585 Weber/Marelli system uses MAP sensor and air temp to calculate air meterage rather than a big flap.
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Vincent
Joined: 20 Nov 2007
Posts: 1055
Location: Belgium
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| Posted: Mon Nov 04, 2013 9:36 pm Post subject: Re: Ghost in the machine |
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| myothercarsanerskine wrote: | | Thanks for that Vincent. Short of replacing the debit meters, how do I test them? |
You may ask a LUCAS or BOSCH or xxx injection specialist to test them; some are really efficient ( at least near me ). Or an AM heritage workshop...
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Vincent
Joined: 20 Nov 2007
Posts: 1055
Location: Belgium
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| Posted: Mon Nov 04, 2013 9:38 pm Post subject: |
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| jonc wrote: | Ah - EFI - I was assuming carbs.
Vincent - debitmeter is an air flow meter right? The V585 Weber/Marelli system uses MAP sensor and air temp to calculate air meterage rather than a big flap.
[URL=http://s1238.photobucket.com/user/joncuk/media/Lagonda/Reference/file_zps2e21addc.jpg.html][/URL] |
Quite right ! It's an electronic part. Thanks for the translation.
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jonc
Joined: 21 Sep 2010
Posts: 584
Location: Cheshire, UK
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| Posted: Mon Nov 04, 2013 9:52 pm Post subject: |
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There is an AML training manual for download on the Technical page http://lagondanet.com/technical.html which explains the system.
"AML LTD TRAINING MANUAL EFI 585 ENGINES" |
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