Flat spot at around 4k Rpm?

[iimushroomzii]

Basically my 1.6 16v Coupe seems to have developed a few flat spots about 3.5-4k.. wondering what it could be? Only seems to happen when its being ragged too, slow acceleration and its fine...

 

[iimushroomzii]

Any ideas ladies??

 

[Rossy197]

Wool in your airbox ?

 

[iimushroomzii]

^^^ haha wish it was that simple.
This is happening more and more often now, anything I should check???

 

[iimushroomzii]

Also the engine management light flashed the other day while this was happening, if thats any help

 

[mini-valver]

Still got the cat in?

 

[iimushroomzii]

Yep..

 

[jordan172]

spark plugs?

paul ly-182`s old 172 had a flat spot at 4000rpm it kind of misfired we changed them and it was fine

 

[mini-valver]

Was it the emissions light that flashed up?

 

[iimushroomzii]

No mate the engine management light, think plugs will be the first point of call though, I've been ignoring it hoping it would go away but it hasnt!

 

[mini-valver]

Under the immobilisor light?

 

[sideways danny]

lambda sounds likely. 4k is a common closed/open loop switch point

 

[iimushroomzii]

Under the immobilisor light?

Under the rev counter..

 

[mini-valver]

Thats what i was about to suggest. WIll only be the first llambda so I'd be tempted to swap the up bank and down bank llambda's and see if it helps. The second llambda only tells you if the CAT is working so wont have a detrimental effect on the running of the car.

 

[mini-valver]

Under the rev counter..

Sorry, I was going from a Clio, like a r****d,

 

[iimushroomzii]

So swap the first and second lambda sensor and see if that works?

 

[sideways danny]

So swap the first and second lambda sensor and see if that works?

yup. Unless you know anyone with diagnostics, in which case, just plug in

 

[mini-valver]

Aye, you dont even need to plug the second llambda in. Just make sure the wire is long enough on the sensor that was originally behind the cat.