Tvr tuscan misfire.

[richard exley]

So my TVR has a misfire, it's more prominent at idle and settles out more at higher rpm.

I've removed the cam cover and inspected the followers, cam lobes ext ext, and they're all fine.

I've recently balanced the throttle bodies, all drawing the same amount of air...

When putting your foot down, the car stumbles until you get into higher revs...

I did have issues with water getting down into my spark plug wells cylinders 1 to 3...

Would the symptoms I'm describing sound more like a simple HT lead issue, or do you think it sounds like something more sinister like worn throttle pots from the symptoms I'm describing...
The misfire is on the driver's side exhaust, so somewhere on cylinders one to three

Misfire appears to be worse when hot.

Also HT leads haven't been replaced in 4 years...

I'm also experiencing an issue with an erratic speedometer, I've re soldered all the dry solder joints, and recently replaced the speedo transducer which I've adjusted multiple times, the issue seems to come and go intermittently... I'm running out of ideas...
Thanks for anyone that has any input that can point me in the right direction to sort the fault.

Edited by richard exley on Thursday 9th July 17:46

Edited by richard exley on Thursday 9th July 17:47

Edited by richard exley on Thursday 9th July 18:06

Edited by richard exley on Thursday 9th July 18:14

Edited by richard exley on Thursday 9th July 20:07

[nawarne]

Are you absolutely happy with the lambda sensors?

The adaptives are quite well out of range....given that you've re-balanced throttle bodies...again, assuming you've got them set around the 6l/sec range across all six cylinders?
Have you tested for air leaks around the throttle bodies/cylinder head flange?

A few years ago I had an issue with the throttle return spring not properly closing the butterflys. Lifting the throttle cable crank pointed me in the right direction. Once I'd got some 'compression' on the spring, I was able to properly adjust the airflow through the TB's.

You mention HT leads. Might be worth changing, will give you a chance to re seal the spark plug cover and stop the water ingress on 1,2 & 3 plug wells.
And, have you any record of when the coil pack was last changed?

A bit rambling, but just my thoughts. Nick

[Basil Brush]

How long since your valve clearances were done? It sounds similar to symptoms mine had when an exhaust valve gap had closed up.

[Snaaakeey]

Close 123 a little. open 456 a little( think that's the right way around) . Zero your throttle. treat 123 as a single cylinder and closed loop lambda. treat 456 the same. You will probably get it into a good running order with 0.5 flow between the 3 cylinders in each bank. . If you cant it may be air leak or throttle body issue or clearance. Remember you only need to adjust the master idle to get 456 right. Then the grub screw between 3 and 4 will move 123 all together. This isn't a perfect sort of setup as each throttle body is slightly different in fit / tolerance so don't chase perfection of balance. just get those AFRs in the right ball park +- 15. Reset throttle and see what happens.

[richard exley]

Thanks everyone for your help, cars running perfectly now, checked valve clearances and they were all fine, checked compression that was all good, but when removing spark plugs I found corrosion on the end of the plugs, cleaned them up, replaced the HT leads and it's not running a treat!

However I have developed another issue... 😅😅😅

Any idea on where to start on this one would be great...

Speedometer behaves erratically... Sometimes you can start the car, go for a drive and the speedometer behaves smoothly... Other times it'll bounce around a bit... A few times it has dropped out completely... I replaced the transducer 12 months ago and everything was working fine when it was replaced.
If you're doing 40mph it'll fluctuate anywhere between 20mph and 50mph and occasionally it'll sweep all the way to 190mph and then drop out to 0...

If I really drive hard and hit over a ton, it'll often drop out completely...

I did have a load of dry solder joints on the dash PCB a few months ago, which were causing all sorts of issues, I re soldered them all, and everything is working... Just the bloody speedo causing me trouble 😅

Any ideas?