Lumpy @ 2K

Hi, Lately the C2 is a little lumpy at around the 2K rev mark. She seems OK after this but just seems a little off colour. The car gats a good long distance work out at least twice a month, and a little round town stuff mid week, probably only 10miles a week. Any medical advice gratfully received :nurse:

MAF? Wont hurt to clean it periodically (unless you break it, then your wallet will be in acute pain for a few days) Carefully remove the MAF from air intake (wired in thing on air intake pipe after airbox/before throttle body). It is clip in, but don't bother - the clip is round the back and a pain to depress properly. Just unscrew two retaining bolts on holder (Torx heads - cant remember if it is T15/25 or similar). Wash MAF gently in IPA (Isopropyl Alcohol) - I have heard people use petrol, but I don't wash my PC's electrical components in petrol, so I don't see why I should wash my cars electrical bits in it either! I use an IPA aerosol spray so this tends to "blow off" debris aswell. If you use a jar of it you will need to agitate. Dry (shake gently to remove excess and any debris/oil in solution) and return to air intake air intake pipe. You may also like to reset ECU to re-learn characteristics at the same time:

Not quite. Switch the ignition on for 60 seconds, and then switch it off for at least 10 seconds. If you switch it on before 10 seconds have elapsed, it may not reset the adaption values. The MAF clip on the early C2s is much easier to get off than the C4, btw.

Thanks GT4 Do you know the reset procedure for a 02 Facelift C2? is it differant from the procedure you mentioned earlier. Also cleaning, is it a matter of spraying the whole MAF unit, or are there any areas you need to mask protect etc Thanks M :worship:

02 model will be fly by wire so what Richard said is spot on from the tech manual, 60 + 10. Cleaning the MAFS is a temporary measure, to do this you need a chemical that completely evaporates, circuit board cleaner is best (from a computer shop etc) the MAFS works by heating up an element, this is know as the hot wire / film. When cold air passes it lowers the temprature of the wire, this drop causes resistance, the DME uses this information to alter fuelling. When you clean the wire your chances of getting it back to factory setting is similar to winning the lotty. It does sound to me like the early stages of MAFS failure. Trying TB reset costs nothing so that would be the 1st obvious thing to do.

thanks guys, Its not too bad and am parking her up for a while so will attend to it in a week or so and will report back thanks as always! :thumbs:

Sorry to bother, So just before I pull stuff apart, on the fly by wire cars you do not need to disconnect the battery? is that correct? Just do the 60 +10? Thanks M :?:

Yes - just 60+10. C2 prefacelift = battery disconnect All C4 and all facelift = 60+10

Thats Brilliant, One last thing, it is OK to spray clean whilst still connected to the cable, as from the earlier thread cable removal a pain? Sorry to ask all this stuff but practical novice! : :dont know:

As long as it is not on - else you might have a flame thrower and a torched MAF! IPA is used all the time to clean electrical components in industry (and the home amateur and other things!). It evaporates quickly without residue (except dissolved dirt if you haven't flushed it completely) and therefore once evaporated may as well have never existed. The MAF is a hot-wire mass air flow sensor. It senses the speed of airflow by comparing temperature differences between a heated wire with and without airflow. More air means the hot wire is cooled more, less air means it is cooled less and hence hotter. The resistance, and hence voltage in/across the wires changes due to the temperature and it it this that is compared in the ECU (or other feedback circuit in older designs). So as long as the MAF is not operational during cleaning or whilst the MAF is not fully dried you will be OK. So shake well (but gently) and leave it 1/2 hour or more after cleaning if you are unsure.

As GT4 says, MAF is a good candidate for this fault. Be worth checking the DME fault memory aswell.

Can wayward coil packs bring about rpm dependent glitches? Another avenue if still no joy?

We normally find they don't work through the rev range when they play up but theoretically I suppose they could do.

Initial coil failure causes a lumpy tick over, when they get worse they then have an impact on the performance, revs, flat spots etc but by this time you'll have P030* codes stored where the EML will stay on. The MAFS does not bring the EML on which confuses me but this seems to suit the complaint better. As said earlier the DME will usually store some information, try and avoid disconnecting the battery and get PIWIS plugged in to get the data, it could be useful.

Llyod Six Being thick here, but do you think that coil packs, or MAFS most likely?I wasnt clear from your post. Thanks M :?: