Slight misfire at low load, worse at high revs

[Noisy]

I have just bought another Tuscan, the car was only serviced 2 weeks ago by a well respected indy, when driving, once its warm it seems a misfire develops, I'm thinking its probably be coil pack, seem to remember having similar with the Noisy one

Also there is a strong smell of petrol when driving, I have checked under the bonnet and can't see any leaks.

Any suggestions?

[mrcyeo]

Did you check the fuel pump?

[nrick]

Hi and glad you are back!

Coil pack is most likely, misfire should start around 2-3k under load. Best to swap the coil packs over for a known good one, I have a spare if you are near (Glos), could also be that there maybe something else :-

Leads/plugs
throttle body sync
worn throttle bodies if they don't stay in sync long
lambdas etc

Have you put it up on the diagnostics? What are the adaptives etc? Have you reset the throttle positions?

[Noisy]

I never left, just bought this one as well while the Noisy black one is being rebuilt and resprayed etc.

I haven't yet checked the throttles etc, but seeing it was service 2 weeks and less then 200 miles ago I would think they should all be ok.

I will get the laptop on it, I don't think I have a spare coil pack at the moment, but can get one from my local suppliers when they open tomorrow, annoyingly I left my other one on the engine which is still at Str8six being rebuilt.

I did think possible throttle pot problem but does feel more like breaking down under load, I have a couple of spares though so could try that.

[nrick]

Ahhh just being greedy then

Which one was it?

Forgot the throttle pots as well.

I had the same symptoms,changed the coil, leads, plugs, coil and then sync'd the tb's runs like a dream, well until I took it apart

[rm55]

When I got my Tuscan it used to have quite a strong smell of petrol. When I took to it STR8-6 after a few months they said that the fuel hoses had perished and were leaking. They replaced them but I still noticed the smell - usually just after starting it up.

It was only after a faulty throttle pot was replaced changed that the petrol smell went away.

[Basil Brush]

When were the valve clearances last done?

[Noisy]

Valves were done 2 weeks ago, I put on another coil pack and seems better, but needs a good run to see if its actually gone.

[Noisy]

Quick up date to this thread, changed Lambda, leads and coil pack, still had the misfire, then replaced the throttle pots, instantly smoother, misfire has gone form the top end and the lumpy bit at 3000 as well, the laptop wasn't showing any faults and the readings from the live data looked ok, but still seems it was the issue.

[Fad Sucker]

could you give me an idea of how much it is be to replace the TB's - i have a similar problem. thanks

[nrick]

Wear in the throttle bodies can knock the pots out, they'll be a bh to keep in balance if there is any wear?

Might be worth a look.

[Robertjp]

Think you can replace the Throttle pots for around £80, blue one is a bit more expensive than the white one. Try tvrcarparts.com

One word of caution with just replacing the throttle pots - they can mask the real problem!!

The throttle pots have their own internal body and spring mechanism, if your throttle bodies are worn (any 2000-2005 cars with 25k + miles on will have this issue to some extent) this has probebly lead to wear in the pots (from excessive movement in the throttle body spindles). Replacing the pots may solve the problem temporarily but they will quickly wear again if there is still movement in the throttle body spindles.

All i'm saying is check your throttle bodies carefully!!

[Noisy]

I replaced the throttle bodies on my other tuscan with rebushed ones, but the spindles on these don't seem to have much play so just opted for throttle pots to start with.