Paging Tim: T5 still misfiring

Hmmmmmmmmmmmmmmmmmmmmmmmm. *ponders*

Perhaps it did not idle long enough to start spluttering whilst the emissions test was being carried out?? I doubt it would pass if it as misfiring / spluttering...

Anyhow, very difficult to diagnose these sorts of problems at a distance, but check again for split intake hosery (hoisery?).

Specifically the carbon canister (under near side front bumper and the small bore tubes that run to it. You could temporarily blank it off at the manifold thereby eliminating the canister and purge valve and to-tank hoses and try the car. It may be pulling air or neat fuel when the purge valve opens, which it would do after roughly 3mins of idling (coolant over 60deg, a/c compressor disengaged).

Could you clarify if the ECU is reporting idle fuel-trim too lean or long-term fuel trim too lean please? They are not the same.

Otherwise you are at the stage where you need to be watching live data and seeing what sensor input suddenly changes, or if the ECU suddenly alters fuelling or timing etc, and working backwards from there to find the cause.

It should sit absolutely rock steady at 850rpm for as long as you ask it to, hot or cold.

Tim..

"Tim.." wrote in news: snipped-for-privacy@bt.com:

As I said, it's intermittent. It did it on the way to the test centre, but I don't know if it played up during the actual test. They make you wait in the reception these days :-(

I keep having a look in what precious little daylight I have spare at this time of year. Haven't found any ladders yet ;-)

Didn't realise the purge valve opened at idle, thought it opened while running. In that case, I can try unplugging it, cos I've already tested it and I know it opens and closes properly when 12v is applied. I've checked the one way valves too and they're OK (nasty job - the vapours from the canister taste horrible :-( ). Haven't investigated the canister itself yet because of it's location.

Interesting point you make about the valve opening after warm up.....it doesn't misbehave until it's almost up to temp. Food for thought, perhaps?

The code is P0171. Difficult to get an exact definition on the net, but Digimoto said it meant long term, IIRC. The ECU data shows short term trim at 0% and long term at -25%. I have tried pulling the fuse for half an hour but the -25 is still in there.

I you recall, this problem started after I spent a day hooning it around a track on V-power then returned to normal 95 afterwards. Maybe there's some value in getting that -25% reset to 0? From what I've gathered, long term trim is to do with the injection duration, so is it saying that it can't get enough fuel in with that duration setting?

The OBD software I have is limited because it doen't measure everything and the more you try and measure, the slower the values get updated. I have checked that the CTS is reading properly. The MAF readings mean little to me, but I can see that it's responding as it should so I presume it's working correctly. O2 sensor 1 is switching as it should and sensor 2 is more steady, as is normal. I can't get any TPS reading other than 0%, but I'm assuming that it's software related and nothing to do with my problem.

It fluctuates ever so slightly between 840 and 870, or at least that's what the OBD software says. When it misfires, the revs drop to almost nothing and this sometimes results in stalling. It seems to do it in bouts, rather than persistently.

Thanks for all your help so far.

Stu

oh no they dont you can ask to view the test as they should have a customer viewing area, they cannot refuse you to view it.

Reg.

snipped-for-privacy@hotmail.com wrote in news:1166565706.732074.23700 @n67g2000cwd.googlegroups.com:

Heh.....didn't realise that I had rights in that department. It's only since the new system came out that they've become more strict in that respect. They used to let you pull your own car onto the ramps and loiter around the test bay, but now they tell you to sit and wait while they do it all.

In any case, I'm not complaining cos I always get a fair test done there. They don't miss much and when something is found they will give an advisory rather than a fail if it's feasible to do so. If a bulb is out, they simply replace it for you.

The fee was only £20 until this time last year when the new system came into operation :-(

Stu

snipped-for-privacy@hotmail.com wrote in news:1166565706.732074.23700 @n67g2000cwd.googlegroups.com:

Heh.....didn't realise that I had rights in that department. It's only since the new system came out that they've become more strict in that respect. They used to let you pull your own car onto the ramps and loiter around the test bay, but now they tell you to sit and wait while they do it all.

In any case, I'm not complaining cos I always get a fair test done there. They don't miss much and when something is found they will give an advisory rather than a fail if it's feasible to do so. If a bulb is out, they simply replace it for you.

The fee was only £20 until this time last year when the new system came into operation :-(

Stu

i can understand not letting you drive onto the ramps or loiter for insurance purposes, but they must have a customer viewing area, there should be a notice saying "customer viewing area available" , i do mot's & as long as the customer isnt disturbing me during a test im quite happy for them to view the test & answer any questions afterwards, more people should view the test , most are surprised whats actually involved in a test !!!

snipped-for-privacy@hotmail.com wrote in news:1166566861.604569.217500@

The 'customer viewing area' would be outside the bay doors in this case. Nobody told me I couldn't stand there, but I've seen enough MOTs done to know roughly what goes on and I've certainly no reason to suspect foul play, so I'm quite content to sit inside and chat with the garage owner these days :-). Strangely enough, he *did* let me back the car out myself once the test had been done .

Stu

I'll only take it to places who let me hang around and take the opportunity to look under the car while it's on ramps. Fortunately there are still people who do this. Obviously I don't get in the way etc. And I can offer useful hints on jacking the car at the same time (they still have joys with the BX suspension...)

cheers, clive