Rough running below 2000rpm
Discussion
Guys seems like I have 3 fairly typical problems on my Chimaera 400.
1). When started from cold the car idles ok perhaps a little roughly but when I go to pull away it dies when you let the clutch in unless you have over 2000rpm. It's as if the ECU hasn't sensed that the engine is cold. If you keep the revs up it stutters a bit but will go and then after 2 mins it starts to warm up and is okay.
2). When warm between 1500-2000 rpm it tends to hunt. I checked the vacuum advance which was holed and disconnected it, but the problem remained. I have ordered a new vac advance and will be fitting it this weekend but I have a feeling that this will not solve the problem.
3). The idle is a bit rough, the engine has had it's cam replaced a short while ago with a Piper 272, should be smooth on tickover but it isn't. I have checked all the ignition components, Plugs, extenders, leads, rotor arm, cap and they all seem okay. I'm partly suspecting injectors as I do notice that when checking the timing at idle it appears to occasionally misfire as the mark I use on the front pulley moves away from the pointer momentarily and then returns.
I recognise that these are all many of the usual suspects but would appreciate a few tips on the best way to start tracking the faults, by the way I have cleaned the mercurial stepper motor.
1). When started from cold the car idles ok perhaps a little roughly but when I go to pull away it dies when you let the clutch in unless you have over 2000rpm. It's as if the ECU hasn't sensed that the engine is cold. If you keep the revs up it stutters a bit but will go and then after 2 mins it starts to warm up and is okay.
2). When warm between 1500-2000 rpm it tends to hunt. I checked the vacuum advance which was holed and disconnected it, but the problem remained. I have ordered a new vac advance and will be fitting it this weekend but I have a feeling that this will not solve the problem.
3). The idle is a bit rough, the engine has had it's cam replaced a short while ago with a Piper 272, should be smooth on tickover but it isn't. I have checked all the ignition components, Plugs, extenders, leads, rotor arm, cap and they all seem okay. I'm partly suspecting injectors as I do notice that when checking the timing at idle it appears to occasionally misfire as the mark I use on the front pulley moves away from the pointer momentarily and then returns.
I recognise that these are all many of the usual suspects but would appreciate a few tips on the best way to start tracking the faults, by the way I have cleaned the mercurial stepper motor.
Changing the cam usually means getting the ECU rechipped to compensate otherwise you can get all the problems and issues that you have discussed. Might be worth resetting the ECU to its defaults by disconnecting it.
If it has been happeneing since the cam was fitted then I would think a rolling road session and rechip might be needed. If the car ran all right and then started to cause problems then there is a fault. The butterfly might need cleaning or it could be an electrical ignition fault. Again a rolling road session is often the quickest and easiest way forward if there is nothing obvious.
Steve
www.tvrbooks.co.uk
If it has been happeneing since the cam was fitted then I would think a rolling road session and rechip might be needed. If the car ran all right and then started to cause problems then there is a fault. The butterfly might need cleaning or it could be an electrical ignition fault. Again a rolling road session is often the quickest and easiest way forward if there is nothing obvious.
Steve
www.tvrbooks.co.uk
Guys seems like I have 3 fairly typical problems on my Chimaera 400.
1). When started from cold the car idles ok perhaps a little roughly but when I go to pull away it dies when you let the clutch in unless you have over 2000rpm. It's as if the ECU hasn't sensed that the engine is cold. If you keep the revs up it stutters a bit but will go and then after 2 mins it starts to warm up and is okay.
2). When warm between 1500-2000 rpm it tends to hunt. I checked the vacuum advance which was holed and disconnected it, but the problem remained. I have ordered a new vac advance and will be fitting it this weekend but I have a feeling that this will not solve the problem.
3). The idle is a bit rough, the engine has had it's cam replaced a short while ago with a Piper 272, should be smooth on tickover but it isn't. I have checked all the ignition components, Plugs, extenders, leads, rotor arm, cap and they all seem okay. I'm partly suspecting injectors as I do notice that when checking the timing at idle it appears to occasionally misfire as the mark I use on the front pulley moves away from the pointer momentarily and then returns.
I recognise that these are all many of the usual suspects but would appreciate a few tips on the best way to start tracking the faults, by the way I have cleaned the mercurial stepper motor.
Low rev problems from cold could just be running slightly rich or dirty plugs, although if there was an ignition fault it would make this worse. If the strobe light is moving wrt the timing marks, that suggests to me that the ignition timing is not constant. Could be a loose distributor (or badly worn drive maybe?), faulty/loose vac advance unit, or some other fault within the distributor like maybe a dodgy rotor arm or something. Are you confident that the cam timing is correct, and has the fuel map been set up to suit it?
Cheers,
Peter Humphries (and a green V8S)
I'm planning a session on a RR with Mark Adams in January as I suspect it's a combination of a fault and the fact that the fuel map isn't yet set up for the cam. I'm going to put the ECU on a fault code reader at the weekend so I should be able to rectify any basic faults prior to the session.
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