Engine 850: B5234TR/2.3/20v/T5R: Sooty Plugs, judder at low revs

[Jod T5]

Originally Posted by Engineer

George the O2 sensors only work on closed loop on our old cars mate so full WOT probs should not be an issue.

This is exactly the reason why so many of these cars have problems...At WOT the lambda stops operating, therefore removing the lambda's ability to adjust the fueling, which is why so many T5's suffer from juddering, usually due to a intake leak.....
I know these are old cars we have but the lambda is crutial, this is why often the cars run crap after they a warm, when closed loop takes over......
cheers
jod

[Georgey dee]

I'm leaning towards the lambda or Maf as it is definitely worse when it's cold or when it has been running at constant speed for a while (IE cooling down) . It's a pitty really as the problem is only up to 4000Rpm then the fault seems to just 'turn off' Wierd!!

Is this when the lambda goes closed loop? If so that would make sense.

Luckily for me I have a top bloke localish to me, (Dooby) who has offered to swap some bits over.

Is this fault an Exhaust gas temp issue? is it because when it's hot it's less efficient therefore not as noticeable? Is it because in winter the temp differences are massive therefore more noticeable????



George

[AndysR]

You don't think it could be the camshaft timing is out by a tooth do you?

[Jod T5]

Originally Posted by Engineer

As a side note your not related to irf are you?

lol, imagine a bendy bus round marham.....
cheers
jod

[Jod T5]

Originally Posted by Georgey dee

I'm leaning towards the lambda or Maf as it is definitely worse when it's cold or when it has been running at constant speed for a while (IE cooling down) . It's a pitty really as the problem is only up to 4000Rpm then the fault seems to just 'turn off' Wierd!!

Is this when the lambda goes closed loop? If so that would make sense.

Luckily for me I have a top bloke localish to me, (Dooby) who has offered to swap some bits over.

Is this fault an Exhaust gas temp issue? is it because when it's hot it's less efficient therefore not as noticeable? Is it because in winter the temp differences are massive therefore more noticeable????



George

"In closed loop operation the ECU uses one or more oxygen sensors as a feedback loop in order to adjust the fuel mixture. This gives the name ‘closed loop’ from the closed feedback loop. The ECU won’t run in a closed feedback loop all the time, so ‘open loop’ is used to describe the operation of the ECU when the mixture is not being adjusted in this way (usually when the engine is cold or when running under high load)., ie WOT

In closed loop operation the ECU uses the oxygen sensor to tell if the fuel mixture is rich or lean. However, due to the characteristics of the oxygen sensor it can’t tell exactly how rich or lean, it only knows that the mixture is richer or leaner than optimum. The ECU will enrich the mixture if the oxygen sensor shows that the mixture is lean, and lean the mixture if it looks rich. The result of this is that the mixture will swing back and forward around the stoichiometric point."
i quote because i could not put it better myself......

Originally Posted by andyrs

You don't think it could be the camshaft timing is out by a tooth do you?

a possibility.......

Originally Posted by Georgey dee

Luckily for me I have a top bloke localish to me, (Dooby) who has offered to swap some bits over.

Pete knows his stuff.....
cheers
jod

[Georgey dee]

I had the timing belt changed about 2 years ago but could it have jumped a tooth?

Or could it be the cam position sensor missing a pulse or two?

I'm guessing it's lambda or MAF because it so temp related.

George

[AndysR]

Originally Posted by Georgey dee

I had the timing belt changed about 2 years ago but could it have jumped a tooth?

Or could it be the cam position sensor missing a pulse or two?

I'm guessing it's lambda or MAF because it so temp related.

George

I suppose it's possible it has jumped a tooth but unlikely, I was thinking more on the lines that the belt might have been changed fairly recently and fitted incorrectly at the time. However if the fault only occurs at/above a certain temperature then I wouldn't suspect the cam timing so much. It could be the cam position sensor but I doubt it.

So just to check the fault you have is juddering when accelerating? and a sudden surge of power at 4,000 rpm? I assume the later is under wot but the juddering at low revs is this under light throttle when warm and not when cold? It might be that your mixture is wrong when the car is warm? I am assuming you don't know whether the 4,000 rpm fault occurs when its cold because you would wait for the car to warm up before flooring it? Just another thought but have you checked the idle control valve? This could be sticking which will affect and produce faults you describe

[Georgey dee]

Very true, that' one of my pet hates, I never drive hard or at high revs when the car is cold, It's an engine KILLER.

When I mean temp I mean outside temp or engine bay/exhaust temp because if it has been driven at motorway cruise speeds the engine bay/ehaust can get very cold on mine.

It happens under medium to hard acceleration when the boost spools up. Then if you keep accelerating at the same rate it magically disappears at 4000rpm.

[Jod T5]

Originally Posted by Georgey dee

It happens under medium to hard acceleration when the boost spools up. Then if you keep accelerating at the same rate it magically disappears at 4000rpm.

Sorry george, its not helpful, but im sure its down to an inlet leak, the symptoms are sure fire......
Too much juice, not enough air..., compensated during closed loop, noticable in open loop...
cheers
jod

[Georgey dee]

The only thing left in the IC system is the intercooler,, I really hope it's not that. Or could it be a turbo problem? Maybe an internal leak.

George