Chimaera low end poor running

[Ian bevab]

I am new to TVR ownership with a 1996 4.0L Chimaera with 71K miles.

I put the car in with a TVR specialist dealer after I bought it for a full service and tune but the car continues to have what seems to be a misfire (or poor running) when it is warm at sub 2000 revs. Plugs and leads have been replaced. At higher revs pick up is smooth. Also it does not always settle to tick over immediately and sometimes stalls.

I can get round the problem by keeping revs high. Could any of you guys help. Is this me being soft and not used to the way a TVR runs or is there a problem? The TVR guy believes the car is running ok.

Sincere thanks in anticipation
Ian

The TVR dealer seemes to think it is ok.

[cerby4.5]

Have you checked the stepper motor? Needs to be regularly checked and cleaned! (Don't know what it does?? but know it affects idle, so may be part of the problem). Easy enough to do so may be a quick fix?? Cerby.

[Cider Andy]

Stepper motors are a cracking little device, Cerby. As the name suggests, it is actually a motor, but one which you acurately control how far it turns, eg. you could tell it to turn a tenth of a revolution, or 50 revolutions or 1023.4 revolutions or whatever. It starts and stops very rapidly, unlike a normal motor.

Quite what its application in the engine is, someone else will have to enlighten us. My guess is it operates an air bleed screw - that's certainly what it appears to do.

[daxtojeiro]

Hi,
the stepper is used to control the rpm. It bleeds air in as you rightfully say, by changing the position of a plunger. During cold starts and running it will be open a lot more than it is when its warm so as to keep more air coming into the engine as the ECU will be adding more fuel too, this ensures the revs are high so it can run rich during the warmup period. When the engine is hot it is used to hold the engines rpm at a nice value, so if the lights go on, or the airconditioning goes on then theres a large load from the alternator and the engine will slow down, the stepper opens up a little to allow the engine to tick over at the correct rpm again. I would clean it as they do seem to be trouble some, but I think it will be your coil or the amp module personally.
Phil

>> Edited by daxtojeiro on Monday 15th August 10:28

[Ian bevab]

Guys

Thank you. Booked in to sort stepper motor and coil. Fingers crossed! Fab car though

Ian

[stringbag]

Ian, clean the stepper yourself and save some cash for
www.tvrcc-south-wales.co.uk/stepper.asp

[parrot of doom]

You can do both jobs yourself, they're not hard. Just be careful not to overtighten the stepper motor - just turn it beyond finger tightness.

Also, make sure you don't just clean the stepper motor but also the housing!

>> Edited by parrot of doom on Tuesday 16th August 00:23

[just_william]

stringbag said:

Ian, clean the stepper yourself and save some cash for <a href="www.tvrcc-south-wales.co.uk/stepper.asp">www.tvrcc-south-wales.co.uk/stepper.asp</a>

Cheers for that link, now know where your all talking about. Think the spanners might be out this weekend just to see what state its in. Nice one
Jimbo

>> Edited by just_william on Tuesday 16th August 08:00

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all together now...

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