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[Andy A]

2003 manual 2.2 petrol.

When I'm travelling down the road at a constant speed of 30mph the engine would lose power for a moment and then gently come back in while keeping the throttle in the same position.
Then the other day it started to do it again, but this time for 2-3 seconds at a time. Some days it doesn't do it at all. There are no codes showing. What could cause this?

Not sure if this is to do with above. The car idles around 1300rpm then slowly drops to below 1000. Lately it has be doing that but as soon as the rpm's go above 2000 they hang there for far too long and it makes changing gear a pain. After less than a minute it hangs for a short time as normal for changing gear smoothly. 

Thanks

[omegod]

Could be camshaft sensor starting to break down ( if it's petrol) they don't always show codes and when they do it tends to be for random transmission ones, then again it could be something completely different 

[Doctor Gollum]

What was the fuel level?

[Bigron]

Omegod beat me, but my answer is probably silly: do you have cruise control, and could it be "having a moment"?

Ron.

[Andy A]

What was the fuel level?

It does it on a full tank as well.

[Andy A]

Omegod beat me, but my answer is probably silly: do you have cruise control, and could it be "having a moment"?

Ron.

Yes I fitted a cruise control after I got the car.

[Doctor Gollum]

When was the throttle body last cleaned? Worth doing if not done for a while, but it does sound electrical

Incidentally what were the radiator fans doing at the time?

[Andy A]

Could be camshaft sensor starting to break down ( if it's petrol) they don't always show codes and when they do it tends to be for random transmission ones, then again it could be something completely different 

Yes it is petrol. I was thinking similar but it is expensive just to try.

I have added some more info to my 1st post.

[Andy A]

When was the throttle body last cleaned? Worth doing if not done for a while, but it does sound electrical

Incidentally what were the radiator fans doing at the time?

Not sure Al. But the engine temp was good. Why?

Throttle body is still sucking well from the cam cover at idle. If I have this right, would suggest that it is fairly clean?

[Andy A]

When was the throttle body last cleaned? Worth doing if not done for a while, but it does sound electrical

Incidentally what were the radiator fans doing at the time?

Not sure Al. But the engine temp was good. Why?

Throttle body is still sucking well at idle after pulling hose off the cam cover and stick my thumb over the end. If I have this right, would suggest that it is fairly clear?

[Doctor Gollum]

Sticky throttle butterfly might throw the ecu as it constantly adjusts it even at a set speed on a rolling road... tweaking to compensate for varying load.

Fan question was because them switching on and off will create a current drop/surge, exaggerated by a weak battery or alternator... enough of a drop and the ecu voltages go to cock.

Run through Kevins Starting/Charging guide to rule it out, and make sure all the fans spin freely engine cold and off... don't want to lose a finger if they start automatically... if one is siezed that will have the same effect on the voltage

[Andy A]

Sticky throttle butterfly might throw the ecu as it constantly adjusts it even at a set speed on a rolling road... tweaking to compensate for varying load.

Fan question was because them switching on and off will create a current drop/surge, exaggerated by a weak battery or alternator... enough of a drop and the ecu voltages go to cock.

Run through Kevins Starting/Charging guide to rule it out, and make sure all the fans spin freely engine cold and off... don't want to lose a finger if they start automatically... if one is siezed that will have the same effect on the voltage

Thanks for the info Al, much appreciated. 

Will check the fans and go through Kevin's guide and check all is OK.

I will take off the throttle body and clean it again. Only done 2000 miles/a couple of years since last done with brake cleaner. I have just purchased some proper carb cleaner this time, because it has some lubricating properties in it so far as I can tell.

[mandula]

I've got similar symptoms (and similar car) with power lose, but only once a month or so. For me, driving with my own leg (not with cruise control I mean ) the car feels to shut down or something, drive just stops for a second and then comes back and drives normally. No codes after that showing. My bet is that there is something wrong with wiring's or connectors between throttle body and pedal.

For high idle, again, I had same symptoms. It was caused by cracked exhaust manifold and leaking pipe joint after 2nd lambda. Fixing those fixed hanging revs, especially when cold engine.

[omegod]

I'm breaking a 2.2 auto that drove fine if you want/need any bit's n bob's

[Andy A]

I'm breaking a 2.2 auto that drove fine if you want/need any bit's n bob's

Do you have an original cam sensor?