£200 and still misfiring

[SlowRider]

The 400 Chim has been running badly at low revs for the past week so took it to Offords today. They've replaced the spark plugs extensions and leads, but seems they were fine all along. Also changed something on the distributor for the vacuum advance.

All this has helped only in that it has made the misfiring intermittent rather than constant. Still not good. I've changed the distributor cap and rotar arm (just cos i had old ones).

Is this practice of diagnosis by replacement the usual way of finding a fault? I would have thought things were a little more scientific by now.

As things are a bit better with new leads etc, is there logic in my replacing the plugs as well? Have a feeling the coil might be at fault. Whats is clear is that as you accelerate its horrible and lumpy until you reach 3,200 rpm and then its takes off.

I would go back to Offord but they are 70 miles away. Or I would go to TMS but I have already wasted £200 on this.

thanks for any suggestions
Jeremy

ps Yes i have cleaned the stepper motor!

[S4CJO]

Was it TMS who charged £200?

Dealt with Offord, value you money excellent.

[tvrinbfg]

Try TVR Power Coventry or Central TVR Stourbridge

[HarryW]

I see you have cleaned the stepper then . Don't know how significant it is but if it clears above 3K2 rpm that is when (or it might be 3K) it comes out of close loop control i.e. lambda control for emmissions .

Definately worth getting someone to diagnose it properly, rather than changing all the bits piece meal, anyone can do that, including me .

Personally I'd be a tad disapointed if that is the level of diagnostic skill of a main dealer technician. I often wonder why you have to pay while they learn on your car , best of luck.

Worth trying Power though if they are local to you, talk it through with Dom he knows these lumps inside out and back to front.

Harry

[Dunc B]

Only had one experience of the garage you mentioned first and IMHO they were C**P,voted with my feet and never used them since

[joospeed]

it's quite common to use the "change component see if it's better" route, I do it .. however if you change something and it doesn't improve it, how can you charge for it? .. put the good item back on and change something else.

agree with Harry tho .. if it's only part throttle misfire under 3500 revs look at the lambda controlled fuelling, if it's there on full throttle under 3500 revs it's summink else ..

demand your money back!

[BraemarBlue]

Agree with Dunc B.

After them, I took it spluttering to Steve Howard who put it right straight away. The inlet manifold was loose! Been brill ever since including 5000 mile around europe this summer.