Engine characteristics

[Skinful]

Can anyone help me with the following.
I have a 99 V6 Manual Cougar.
When I am cruising down the motorway the engine "coughs". No reduction in speed; the "cough" doesn't last long enough, only a fraction of a second but enough to feel it.
Also, is it normal for the engine management to cut in when decelerating at around 2 - 2500 rpm, ie that is when you first feel engine braking and the engine "free wheels" before that?
If not then any ideas?
Car is still under warranty and chaps at Ford are continuing to investigate but any information you could give me would be helpful.
Strangely no error codes from ECU.

Cheers,

Mike.

[NARD]

:)Does the coughing occur when the A/C is on? This could be responsible for slight power fluctuations!!

[Skinful]

Yes it does but the coughs are sometimes too close together for the A/C to be cutting in and out, I think!
:confused

[Relaxitscool]

Also, is it normal for the engine management to cut in when decelerating at around 2 - 2500 rpm, ie that is when you first feel engine braking and the engine "free wheels" before that?


My car suffered this problem after I installed a Green Cotton filter. Now I've got a lot more air being forced rather than sucked into the airbox the engine slows smoothly when I take my foot of the accelerator. It could be just coincidence. Have you checked the obvious? Don't trust garages to do this, it could be a simple as a naff spark plug or a blocked air filter..