Lumpy engine

[mcharman]

dear all
i have posted on this topic before and would be grateful of any advice.
I have a 93k Chimaera 4.3 which does not run smoothly at low revs (eg when travelling at constant 30mph). It is currently in blackpool with some ex TVR mechanics who are having trouble findimng the fault. One of them suggested that the 4.3 big valve should run like this and that it was normal. Is this right and can anyone offer any help? Regards Mark.

[ssc1]

I have a chimp 4.3 dont know if its a big valve though and it does run smooth at 30mph in the lower gears and even in top its not what i'd call lumpy ,and it pulls well from 30 in top and very smooth right up to the redline...

[shpub]

Certainly common on 500s which have a similar cam.

Steve
www.tvrbooks.co.uk

[2 sheds]

Depends how bad it is, I would expect the 4.3BV to be a little lumpy below 2,000 rpm , but the term lumpy is subjective, The 214 cam (which it proibably has) has a power band from around 2,500 rpm at lower revs you can experience reversion, this is strong pulses back into the plenum and out towards the airflow meter, and the result is that the airflow meter gets the wrong message/ reading the result being a rich mixture, in effect it can measure the air twice, Its common with hotter cams, this is the price you pay for all that power !!! But it shouldn't be bad enough to spoil the driving experience.
Tim

[apache]

I have this prob too, I notice that if I temporarily disconnect the ecu it runs smoothly for a while then becomes a moody bitch in traffic again. I had a spin in Marshy's Chimaera and it was noticeably smoother but on the open road didn't have the rawness of the Griff. Am I reading too much into this, I love my cars open road performance but don't like it's traffic temprament. I feel it is a cam relateds issue but why does the ecu disconnect make a difference?

[shpub]

Disconnecting the ECU resets and puts you into defualt mode. As time goes by the ECU will adapt to the engine and is that means it gets worse then that usually indicates that one of the many fuel injection components is giving duff info or the ECU is playing up.

May not be detected by the diagnostics and really only a rolling road session with Mark Adams would identify wht the problem is.

Steve
www.tvrbooks.co.uk

[beano1197]

My "Improvements for lumpy running I have experienced" list would include:

Run the car every day, and remember it picks up the mood of the driver
ECU connectors - clean
HT leads and caps - replace
dizzy - cleane
coolant - keep it topped up
Optimax - feed constantly and exclusively
left leg - keep up the exercises at the gym


My Griff is running at possibly the smoothest in my ownership. It's as easy to forget that it's still "lumpy" - in the same way that you start believing that it does not have anough power It's all relative.

[2 sheds]

Remapping the fuel will improve this, I wouldn't describe as problem, more a characteristic. Speak to Mark Adams.
Tim

[apache]

met him at this years Duxford and never seem to get to arrange a session....life just keeps getting in the way, one day soon

[manek]

2 sheds said: Remapping the fuel will improve this, I wouldn't describe as problem, more a characteristic. Speak to Mark Adams.
Tim

That certainly improved my car's smooth running which was worth the price of the rolling road/rechip session alone. Got an extra 30bhp as a bonus