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during a 300+ mile round trip visiting the g/f parents (tut) i notice i now have a flat spot in every gear at about 1800 - 2500 revs and its only on part throttle, car still pulls well fully open throttle, but just cruising at 2000 revs has the car spluttering and increasing/decreasing in speed, wondering if this may be a misfire, or has the fuel map on the ecu nackered. its been over fueling for a while and ive just replaced the plugs and leads about 1000 miles ago. if that has any effect on the situation.

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Two things I would check, camshaft position sensor (hall sensor) and idle stabilisation valve for cleanliness. I had a blocked isv and it felt like the car didn't know whether to accelerate/decelerate unless you booted it or let right off the throttle. My knackered camshaft position sensor caused general flatness throughout the rev range but a distinct splutter arround 2000 rpm. Get it on diagnostics if you can, it can save sooo much time!

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you'd really know if the hall (cam) sender was screwed...the car has a lot less bhp. i know this, cause i have that prob at the mo! it does have the huge vibration around 2000rpm as well.

i'd start by cleaning the ISV...easy to do.

then i'd be looking at the coilpack. EDIT: but yours is a dizzy if i'm right, so it can't be that!

[ Edited Tue Aug 31 2004, 03:16PM ]

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cheers peeps. im just going out to clean the isv now, and see if that helps. its funny you mention the vibration andy, cos i have that exact symtom, ive been thinking my suspension bushes are fooked, but maybe the hall sender has something to do with it. what would it do, put the cams out of sync? hence the bad fuelling and vibration? good advice btw. thanks.

doesnt it just seem that all of these symptoms have the same fault, but also all of the faults have the same symptoms. if u get me. im just sick of repairing something, to find it wasnt faulty in the first place. lol. vag com soon...

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the hall sender provides the timing for sequential fuel injection, ie what order each cylinder recieves its fuel, a lot of fuel injected cars fire all injectors at the same time but the vr6 requires the injectors to be fired in the correct order for optimum performance. if they don't then you might notice a general drop in power with a splutter at lower revs. the halll sender also provides a secondary input for the ignition timing i believe

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Also check the throttle body for cleanliness, If it's black then Clean Immediately with carb cleaner until spotless, make sure that there is a very fine gap around the butterfly (if held up to the light!) then reinstall... also check the proximity switch on the throttle body that it's set correctly and "clicking" when the butterfly is open.. ;):D

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well im in no rush to sort out the mounts as the cars off the road from now till its a complete car, he he. got myself the mk 2 i wanted. so my new VT mounts will be going in all round. and the whole car will be getting stripped down and sorted, so expect a lot of what do i need to do questions soon.

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the hall sender provides the timing for sequential fuel injection' date=' ie what order each cylinder recieves its fuel, a lot of fuel injected cars fire all injectors at the same time but the vr6 requires the injectors to be fired in the correct order for optimum performance. if they don't then you might notice a general drop in power with a splutter at lower revs. the halll sender also provides a secondary input for the ignition timing i believe[/quote']

Not true. Sequential fuel deployment is hardwired into the ECU and not governed by the CPS. The CPS governs ignition advance mapping. If the CPS gives an implausible signal or no signal at all, the ECU retards the ignition and uses a failsafe map and uses the crank sensor and throttle position sensors to form a base map which the engine will run on, but not optimally.

VT engine mounts.....get them. You *will* notice the difference. Not only in reduced engine slop, but in better handling too.

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Sequential fuel deployment is hardwired into the ECU and not governed by the CPS. The CPS governs ignition advance mapping. If the CPS gives an implausible signal or no signal at all' date=' the ECU retards the ignition and uses a failsafe map and uses the crank sensor and throttle position sensors to form a base map which the engine will run on, but not optimally.

[/quote']

which is exactly what my car is doing at the mo.

VT engine mounts.....get them. You *will* notice the difference. Not only in reduced engine slop' date=' but in better handling too.[/quote']

seconded...better throttle response as well.

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the hall sender provides the timing for sequential fuel injection' date=' ie what order each cylinder recieves its fuel, a lot of fuel injected cars fire all injectors at the same time but the vr6 requires the injectors to be fired in the correct order for optimum performance. if they don't then you might notice a general drop in power with a splutter at lower revs. the halll sender also provides a secondary input for the ignition timing i believe[/quote']

Not true. Sequential fuel deployment is hardwired into the ECU and not governed by the CPS. The CPS governs ignition advance mapping. If the CPS gives an implausible signal or no signal at all, the ECU retards the ignition and uses a failsafe map and uses the crank sensor and throttle position sensors to form a base map which the engine will run on, but not optimally.

What can I say, the Bentley manual must be wrong, it categorically states the CPS provides sequential injection timing.... hmmm

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