Car failing to idle - solved by a new battery

[ianwayne]

Title says it all but here's what happened.

My friend's Chimaera 500 would just about start (turned slowly) the last week or so and so although poorly, we both thought the battery was not to blame for the fact that it wouldn't idle properly. I'm ahead of you there, stepper motor? So I took it off mine and fitted it to his expecting it run properly and therefore indicate that he needed a new one.

It ran worse! Every time he stopped at junctions or dipped the clutch, the car would just die.

Anyway, fitted a new Varta battery this morning and it's running spot on. Erratic for the first minute of two after driving off but this is likely due to the ECU relearning since the battery had been off the car. Engine now reading 1000-1100 rpm on dipping the clutch, falls to 900 rpm ish a couple of seconds after stopping, like it should. Spinning over a lot quicker too, obviously. I'm thinking that the battery was so bad, it was dragging down the ECU.

For those with shoddy or poor idle, try a new battery. I've learnt it's NOT always the stepper motor.

Edit: Yes we've swapped the steppers back. Mine is a shiny 4 month old one, his is old and black (not shiny) although working OK.

Edited by ianwayne on Wednesday 28th January 17:51

[fausTVR]

Could a weak battery also give a marginal HT voltage at tickover? When my battery died, the engine was much livelier with a new one.

[Milky400]

I had the same, also improved low speed smoothness

[QBee]

Ditto

[adam quantrill]

Improved mine (wedge v8) with a brand new alternator - same difference really. But another thing to try. And slightly cheaper, these days ;^)

[Sardonicus]

No surprise seeing as the injector fuel pulse is dependent on battery voltage even though the ECU as a correction table built into its operating system/programming but it is not an exact correction but without this aid EFI would be hopeless also the fuel pump will not run correctly along with the ign system etc so its all down hill really with a dieing battery and the alt causing excessive load on the motor where its trying to charge the culprit batt

[ChimpOnGas]

Loose battery terminals being another culprit that will give similar trouble.

Loose battery terminals are every common, but completely free to resolve.

well worth checking

[ianwayne]

I changed the battery for him, being the more practical one (?); the terminals weren't loose.

Incidentally, the battery that came out was a Viper Red. Searches online turned up nothing on these at all, but he has a receipt for a Clevor Trevor battery from 2013.

[ChimpOnGas]

ianwayne said:

I changed the battery for him, being the more practical one (?); the terminals weren't loose

I wasn't suggesting your terminals were loose, just recommending that others periodically check the security of theirs.

Loose terminals are very common and can give all sorts of running issues, given they're free, super simple & quick to tighten they should always be your first port of call.

In my opinion everyone should be checking their battery terminal tightness as part of their regular service schedule.

[Sardonicus]

ChimpOnGas said:

I wasn't suggesting your terminals were loose, just recommending that others periodically check the security of theirs.

Loose terminals are very common and can give all sorts of running issues, given they're free, super simple & quick to tighten they should always be your first port of call.

In my opinion everyone should be checking their battery terminal tightness as part of their regular service schedule.

See this a lot on Halfords fitted batteries (non TVR) no seriously

[selym]

I'm not a TVR owner, but this makes for interesting reading. My VX220 sometimes struggles to turn over, idle is poor on occasions(the cams don't help!)and I can't see in the paperwork when the battery was last changed. The problems are more apparent during the winter months.

I'll get on it, thanks.