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Old 2nd November 2019, 12:01   #51
pletevl
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I have replaced (again) the spark plugs, both coil packs and HT leads, all brand spanking new (again)
And no change.
I'm leaning towards a sticky valve now.

Pete.
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Old 2nd November 2019, 21:29   #52
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I don't see how it could be - why would it start fine and then develop? Surely a sticking valve would either be more constant or intermittent...


I would say it has to be sensor or wiring related but I've no idea what it could possibly be!
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Old 2nd November 2019, 22:36   #53
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Because they heat up quicker than the valve guide. So I've been told.
All sensors have been changed except the second lambda.
T4 is saying everything's good so it's not a wiring problem.
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Old 3rd November 2019, 17:14   #54
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Quote:
Originally Posted by pletevl View Post
Because they heat up quicker than the valve guide. So I've been told.
All sensors have been changed except the second lambda.
T4 is saying everything's good so it's not a wiring problem.
I think that is highly unlikely. The parts are manufactured within very tight tolerances and I simply do not believe it would be possible to get outliers where heating up would cause this.
And why should that suddenly have become an issue?. I take it the car has done many miles before this problem occurred.?
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Old 4th November 2019, 22:41   #55
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Before you go to the (relatively) large expense of taking the head off chasing a sticking valve - which I still think is unlikely - I'd still say it's worth trying the relatively cheaper option of a new TPS and maybe wiring loom?
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Old 5th November 2019, 11:58   #56
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I'm all ears to everyone's views on this. More heads are better than one, that's why I put up this question.

The car has done 75000 miles, it's been playing up for about 5 years now, it's OK in the summer, doesn't stall, but stalls in the winter.....

I can't see it being the TPS because even starting the car and not touching the throttle, it starts chugging after 30 odd seconds.

I can't see it being the wiring loom because T4 is giving me perfect stable readings from all sensors. This is why I now believe it to be a mechanical problem.

Pete.
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Old 5th November 2019, 13:17   #57
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I'd also have a look at the T4 live data, see if 1. the chugging is caused by ridiculously long injector times, and 2. if there's any obvious cause to make the ECU start increasing the time.
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Old 5th November 2019, 13:40   #58
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Live data doesn't show me anything strange compared to my other TF that runs fine. around 4.500ms on startup going down to around 2.800ms when hot.
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Old 5th November 2019, 18:02   #59
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There is a spigot on the back of the top part the engine which has a rubber hose attached and the other end goes to a canister on the bulkhead(1999-1600 bubble). I believe its something to do with emmisions?? It was broken but held in place by the tension of the hose. It took a long time to find it was the source of the intermittent roughness and hesitation under load. Just a thought, hard to see things made of black plastic. Chris.S.
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Old 10th November 2019, 22:41   #60
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At a bit of a loss what to suggest Pete, your cause is obviously different to mine though the symptoms are the same.


I see high manifold pressure (i.e. low vacuum) with mine - 80kPa plus when it's cold and misbehaving, and even when hot its only 50kPa (should be 30kPa or so I believe).
No sign of any leaks, and heaven knows I've sprayed enough brake cleaner at it.
That said, it seems to have plenty vacuum if I unplug the unused takeoff...


Side effect of the pressure being haywire is massive overfuelling - injection times of 14ms were noted, which would more than explain the misfire as it drowns in fuel.


I suppose my next step is to replace the inlet manifold gaskets and see if that helps.
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