Black powder from exhaust.

[jamesuk28]

Hi, I have a TVR chim 93 4.0l. Its just had the head gaskets replaced. When i got the car back I NOTICED IT RAN 20c hotter at 90, as oppose to the 70 it always had, I assume that the new thermostat was to blame. Anyway after i got it back it would not start when hot unless you gave it throttle, I assume that the fuel is getting to hot and vapourising, it always starts when cold. Now the car tries to stall when you slow down for junctions ie goes down to virtually 0 revs and then shoots up to around 1800. But the most alarming thing is the exhaust stinks produces black smoke, and now I have a black powder (assume carbon) gently dropping from the exhaust. Any ideas before I throw the towel in and sell the c@@t. Thanks v much

[greenv8s]

Sounds like it may be running very rich, perhaps because of an exhaust leak throwing the lambda readings out or perhaps because of another fault. I suggest you start by giving the stepper motor a good clean and then have a listen for any exhaust leaks, failing that take it to a good TVR specialist to diagnose the problem.

[2 sheds]

90 is OK and better than 70 for normal running temp, wouldn't cause starting problems, the rich running could be faulty water temp sender for the ECU but it could also be many other things so just a guess, base idle/ mixture might just need setting up.
Tim

[jamesuk28]

I cleaned stepper motor a few weeks ago, it wasn't that dirty and I followed the manual, ie was very carefull not to damage the plastic surround near the nut. I altered (I think ) the air mix on top of the plenum as per manual ie screwed down nut and then opened it 2 1/2 turns have altered it again to 3 which is were it was originally and before the problems started. Car has been looked after by Offord TVR. Thanks guys for all your comments I really appreciate them. How would I reduce the mix ie make it run less rich?

[hut49]

Why not take it to someone who knows how to set it up? Frankly speaking, fiddling with this and that on a high performance engine is only going to cause you to throw in the towel, as you indicated your were about to, earlier. The number of variables involved, plus the ECU trying to manage these and get engine performance back on the map after each time you change anything, is always going to defeat you. If cost is the issue isn't there an indie in the area who might be able to use a diagnostics module to sort out the problem.

[jamesuk28]

Cost is not an issue, I have spent over £3000 on the car since October last year!!!. I love the car and today spent 1 hour on autotrader looking for something else. lotus esprit, Bmw 8, mazda rxz etc etc. Even if I had £25,000 to spend the only car I really want is a V8 powered TVR. My efforts at fiddling are only a last ditch attempt so I can hopefully use the car for my holiday starting Friday, otherwise I have to use the Mrs's Clio which does not fill me with glee. That said at least I will get there and back. I suppose iam really just pissed that every time I look foward to using the car for a long jaunt something always happens which means I have to comprimise. Maybe I should just get something a bit more trouble free.