We're still trying to sort out our new-to-us Felicia. Just had a major service and was running a lot better but one thing in particular was bothering me; the engine speed dipped after coming off the throttle then rose to the normal idle speed. Before the service it sometimes stalled, so there was a distinct improvement.

After exercising the search button last night I concluded that the two most likely causes would be a dirty throttle body and a vacuum leak, so this evening I had a stab at cleaning the throttle body. I won't say I did a great job but the cleaning cloths looked quite black afterwards. There was quite a lot of soot in the TB just below the butterfly valve and the plate of the valve was also fairly sooted. I'd guess this has been exacerbated by cool running, rectified by replacing the thermostat and the dual temperature sensor.

After refitting the throttle body cover and the top of the air filter housing I tried it out. The engine speed doesn't dip noticeably now, but instead the engine speed is sometimes very slow to drop, meaning that when I accelerate then change up gear, I have to wait a long time before bringing in the clutch after changing gear to avoid clutch drag!

Any ideas? I didn't notice these symptoms being described when I was searching last night, but I'm tending towards thinking that I need to do a better job of cleaning the throttle body, and I need to start searching for one or more vacuum leaks. Does this sound like the most useful direction to go?

hi,sounds the same as mine,i bought a can of carb cleaner,started the engine with the throttle cover off and held the revs at about 3,000 rpm then i sprayed most of the can into it,cleaned it up a treat and it runs better,also i took out and cleaned the MAF sensor as it gets all the gundge off the throttle body stuck to it when you spray the carb cleaner.

Thanks - that was enough of a clue to search using MAP. The next step will be to have another go at cleaning the throttle body, hopefully doing a more thorough job, then taking a look at the MAP and temperature sensor.

Still having problems with the way the engine revs drop too slowly ...

Have cleaned the throttle body a bit more thoroughly, and also very carefully cleaned the MAP sensor. To make sure the learned ECU parameters aren't causing a problem, I left the battery disconnected, (about 36 hours). I read somewhere that re-initialisation should include turning the ignition on but not starting the engine, (did this for 3 minutes), and/or going for a vigorous drive, (a solid 4 hours of italian tune-up on mostly minor roads).

Have also checked for vacuum air leaks but I can't detect any.

The symptoms are roughly the same, although I'd say the engine is running better than before; when I come off the throttle the engine revs drop smoothly but a little too slow, so I have to wait for the revs to drop before I can re-engage the clutch for the next gear. The rate at which the revs drop seem to be the same whether my foot is on the brakes or not, suggesting this isn't caused by a vacuum leak.

Any ideas?

To me it sounds like a vacuum leak :S .. What you can do to be sure, is spray WD40 around where u think there might be a leak, if you took the throttle bodies off then maybe the connection to the block/manifold is leaking? if it momentarily works ok with WD40 "plugging" the hole than you know where to fix, the other method to detect a leak is on idle spray carb cleaner or that "easy start" stuff where u think there is a leak, if the revs pick up slightly then the spray is getting in and causing a change in revs.

Hope this helps

Yes, I was thinking air must be getting in somewhere ... the first thing I'll check is whether there is any slack in the throttle cable - because if the butterfly valve is being held very slightly open when my foot is off the accelerator pedal that'd account for the symptoms, and it's easy to test.

Turned out the throttle cable had slightly too much slack, not too little. While I was there I noticed the hose to the fuel pressure regulator was in a poor condition, especially at the regulator end. Looking more closely I realised there was a small hole in the rubber so I cut off about half an inch and reattached. This made a noticeable difference. Since then I've replaced the hose.