Hi, I am new to the site but looks like people on here know what they taking about so wonder if anyone can help.

I have a 54 1.6 16v petrol 3 dr Stilo which I have had for about a year but I am having one major problem with it.

All of the time whilst driving the power is irregular and alternates from 100% to 60% every second or so. This is noticeable to me whilst driving but not really to passangers. The power loss is more noticeable when first turned on before heating up.

If I try and hold the revs at say 2000 then this goes up and down between 1800 and 2200 with my foot steady on the accelerator.

I took it to a garage last year and they said it would benefit from a service, which they carried out and this did improve the situation but it didn't solve it. Since then (about 6000 miles) it has worsened. Another garage suggested some Cat cleaner which again improved the situation for a number of weeks but didn't solve it.

Does anyone know what might be causing this and where to start? I am reluctant to take it back to a garage for them to do a diagnostic as the engine light has not come on and there are no recorded faults (they checked last time).

Thanks

Presume you're not getting any error messages on the dash? Ideally you need to get the car plugged into dignositc software.

The problem sounds like fuel starvation, but could also be one or more coil packs breaking down. Coils on the way out do produce some odd symptoms..