Help Diagnose a 6k rpm stutter????

[darrel]

My dealer has my Tusc to find out why there is a misfire at 6000 - 7000 rpm. I first noticed this at 18 months old, but since have had a rebuild (followers / cams) (rebuild No'2) and new lambda's. After 1k service and 2 year service was free to try the high revs again and it still misfires at > 6000 rpm.
My dealer cannot find a problem as it is not readily apparant in 1st and 2nd and only just noticable in third (then you are going a tad too quick for testing on public roads) however in 4th its a definate stutter and in 5th the engine will misfire so badly that it will not pull past 6400rpm (showing 175mph on private land OBVIOUSLY). Does anyone know how this can be diagnosed as dealer does not recommend workshop revving (and I doubt it would be noticable without load anyway) and says nothing appears amiss at lesser speeds..
Any help / advice much appreciated???
Daz

[hut49]

Isn't there a plug-in diagnostics package that you can hook up to the ECU and take it for a run on private land. The data dump should reveal what's happening. I can't believe this isn't readily available technology to an engine specialist .

[claire_scot]

It is possible to log all the engine data when you have a problem like this.
I have had loads of Tuscans with this problem. To diagnose them I took the laptop with the engine data log out in the car with me. It records all the data in graph form, which I look at when I get back from the test drive. 9 times out of ten you can pick up from a reading, the problem.
Shame you don't live in Scotland, as I could guarantee that I could cure your problem.
If I can be of any other help, just ask.

Claire

[donaldhunter]

Claire,

I think we need to do this with my Tuscan sometime soon. It's still got hunting problems at low and high revs under load.

Cheers,
Donald.

[Dai Capp]

donaldhunter said:

Claire, I think we need to do this with my Tuscan sometime soon. It's still got hunting problems at low and high revs under load. Cheers, Donald.

I too am still seeing issues particularly around 2400 and 3500 rpm...

Went out for a 3 hr drive with the dealer last night and whilst it is early days (and the car behaved for the most part - typical) there seemed to be two possible issues. One is that the throttle pots couldn't cope with the under bonnet temperatures and were going off kilter but secondly we noticed a significant vacuum developing in the petrol tank (ie a big intake of air when the filler cap was released). So we are also thinking a fuelling problem.

As I said, early days, but needless to say I'll post again when there are any developments. Also be interested in your thoughts Claire...

All the best

DC

[nutcase]

Darrel,

I've got exactly (and I do mean exactly) the same problem with my 2001 car. As you say, it actually gets so bad at v.high speeds that it's effectively a speed limiter!

Takes the edge off driving doesn't it? I mean, whats the point in having a car that revs to 7300 or whatever when it sometimes struggles to get up there!?

Problem with this is, how the hell is a dealer going to experience the fault without travelling at some highly illegal speeds!?

Difficult one.

My engine is back in Blackpool as we speak for a rebuild (they guess piston let go!?) so i'm hoping this fault may not happen when it eventually comes back.

I'll keep you posted anyway mate.

James

[andyvdg]

claire_scot said:

It is possible to log all the engine data when you have a problem like this. I have had loads of Tuscans with this problem. To diagnose them I took the laptop with the engine data log out in the car with me. It records all the data in graph form, which I look at when I get back from the test drive. 9 times out of ten you can pick up from a reading, the problem. Shame you don't live in Scotland, as I could guarantee that I could cure your problem. If I can be of any other help, just ask. Claire

Is there a common cause then ? I get this about a 1000 miles after each time it's been "rebalanced".

[darrel]

Claire - If it were'nt for the 600 miles, i'd pop over!

James - Damn right and bloody annoying!!! If I'd wanted a car that was limited to 175 i'd have bought a ummmmmm....eeerrrr... limited thingy (no doubt of German origin??). Anyway hope you get yours back from B'pool working (however at the risk of dashing your hopes, mine has only been back a few weeks from rebuild #2 and the problem was not cured). My dealer did suggest a rolling road so that it could be run to 6-7 k rpm and data recorded on a lappie but I am not sure where I can do this reasonably locally.

Andy - What exactly are you having rebalanced?? (Sorry for my ignorance)?

Thanks to all for input - please publicise if a cure is found, as will I ????!!!!!

[lee02]

why dont you try going to a engine specialist with a rolling road you may be able to reproduce the problem in the in a workshop

[joospeed]

If anyone finds out what this mystery 6k misfire is I'd love to know for future reference, things is I've never seen a Tuscan with a 6k misfire so haven't had the chance to see it for myself, maybe it's something in the derbyshire petrol, but Chesterfield Tuscans don't seem to suffer from this at all ...
Joolz .. intrigued.

[dgreaves]

I had this problem - and had it fixed totally (after about 2 years!)

Most noticable at 80-100mph in 3rd gear.

It's the inlet manifold.
The factory (Paul Forrest) knows about it. I think there was a change to the bearings used for some element or other.

David

[joospeed]

dgreaves said:

I had this problem - and had it fixed totally (after about 2 years!) Most noticable at 80-100mph in 3rd gear. It's the inlet manifold. The factory (Paul Forrest) knows about it. I think there was a change to the bearings used for some element or other. David

yeah I'd heard about this .. dreadnought worked the fix out .. is that right Clare? I was wondering why there'd be a pot reading fluctuation when the butterfly is in line with the air flow, surely you'd think if there was going to be any variation due to throttle spindle wear it'd show mostly with the throttle closed and the induction pulses working on the back of the butterfly so generating a large vacuum every second revolution for each cylinder.. this is certainly the case for the 4.5 cerbie .. throttle variation probs at idle, none at wide throttle openings. Does anyone have the answer?

[cgb]

Claire -

where do I get the software ??

c.

[luca brazzi]

cgb said:

Claire - where do I get the software ?? c.

Try a search on Kazaa

Only kidding, I guess its not available to anyone except main dealers, and only runs on Win3.1 anyhow.

LB