Stumbling at 4500rpm

[Imran999]

It’s taken me 3 years to get it running right, but it didn’t last long, it’s now stumbling around 4500rpm - feels a bit like a rev limiter does, although not as clean. If I ease off the throttle it will go past 4500, but if I dig in again with more throttle it will hesitate.

I can’t say for sure, but I don’t think it’s doing this until it’s really very hot. I try hard not to rev an engine when it’s not fully up to temp, so I can’t be completely sure.

New fuel pump, filter, coils (NGK), leads, plugs, t-pot’s and lambda’s.

Any help/idea’s would be greatly appreciated - thanks

[FarmyardPants]

Sounds to me like either lack of fuel or ignition breaking down.

Possibly if the adaptives are doing a lot of enrichment (due to poor setup) then once you go open loop and rely on the map only, you might be running too lean. But then again you’d get the same problem at 3k rpm with a wide throttle..

Something to ponder while we wait for the experts

Edited by FarmyardPants on Sunday 26th September 21:21

[Imran999]

I have really struggled with setup in the past, but this time it went as it should.
I had vacuum gauges on both banks, got them both reading about the same at 1500rpm and then confirmed with a syncrometer on each inlet. Adaptives were slightly positive but close to zero.

I know I should get a PC on it and capture various values while driving, but the only PC I have with XP on it, is like a Soviet era clunker with an 8 minute battery life.

[mrniceguy351]

I had a similar problem till I relocated the coils. Fixed it straight away. They cook being in the valley like that.

[Imran999]

mrniceguy351 said:

I had a similar problem till I relocated the coils. Fixed it straight away. They cook being in the valley like that.

I fear you may be right.
But when I discussed here on the forum a couple of months ago, the general consensus was that they should be just fine in the V, that the temperature doesn’t really exceed 100degC and that longevity is actually quite good.

I’ve had a set of Bosch ones that failed in about 1200 miles, so I replaced them with NGK ones, which are now perhaps falling over at high temperature.

[Byker28i]

Only time I had those sort of symptoms early in my ownership was when the coils failed. Rough running over 4K revs.

[Imran999]

Just in case anyone else has a similar issue, I felt I should report back with the solution.

Switched the (new) NGK coil packs for Bosch ones and the issue has gone away.
Best to steer clear of the NGK coils, str8six also confirmed to me that the Bosch ones were the “only” ones to get.

Of course, being a TVR, I now have a new problem to deal with, but that’s par for the course.

[DuncanM]

Imran999 said:

Just in case anyone else has a similar issue, I felt I should report back with the solution.

Switched the (new) NGK coil packs for Bosch ones and the issue has gone away.
Best to steer clear of the NGK coils, str8six also confirmed to me that the Bosch ones were the “only” ones to get.

Of course, being a TVR, I now have a new problem to deal with, but that’s par for the course.

Oh that's quite annoying but also great to hear you've fixed this

Annoying because I have bought NGK coils as spares, car is currently running beautifully, on Bosch coils that are very old (18+ years).

Did you find a good supplier for the Bosch ones?

[Imran999]

Sorry Duncan :-(

I got my Bosch ones from an Amazon supplier (at quite a decent price), but my NGK ones were bought from autopartspro.co.uk where the Bosch ones go for about £25 each.

The Bosch ones are tiny (by comparison) and make snake-pit installation (and removal) very easy :-)

[Phil.]

I’ve been without a Cerbera for many years. At the time Joolz in Chesterfield was the Cerb guru and I visited several times. He was just excellent. I don’t know what he’s up to now but have found the website below which looks very much like his work. You might save a lot of time and money by asking him to sort yours.

http://www.kitsandclassics.co.uk/TVR-Cerbera-V8-Tu...

[DuncanM]

Imran999 said:

Sorry Duncan :-(

I got my Bosch ones from an Amazon supplier (at quite a decent price), but my NGK ones were bought from autopartspro.co.uk where the Bosch ones go for about £25 each.

The Bosch ones are tiny (by comparison) and make snake-pit installation (and removal) very easy :-)

Thanks Imran, that's a decent price for sure

[Imran999]

Phil. said:

I’ve been without a Cerbera for many years. At the time Joolz in Chesterfield was the Cerb guru and I visited several times. He was just excellent. I don’t know what he’s up to now but have found the website below which looks very much like his work. You might save a lot of time and money by asking him to sort yours.

http://www.kitsandclassics.co.uk/TVR-Cerbera-V8-Tu...

Thank Phil - Jules is certainly around and is still very much the man for getting Cerbera engines running optimally.
Alas, my single biggest regret is that I didn’t send my car to him, before exporting it to Canada :-(

He has been extremely helpful though, a very very decent chap.

[Imran999]

Imran999 said:

Phil. said:

I’ve been without a Cerbera for many years. At the time Joolz in Chesterfield was the Cerb guru and I visited several times. He was just excellent. I don’t know what he’s up to now but have found the website below which looks very much like his work. You might save a lot of time and money by asking him to sort yours.

http://www.kitsandclassics.co.uk/TVR-Cerbera-V8-Tu...

Thank Phil - Jules is certainly around and is still very much the man for getting Cerbera engines running optimally.
Alas, my single biggest regret is that I didn’t send my car to him, before importing it into Canada :-(

He has been extremely helpful though, a very very decent chap.