Rev wobble at lower engine speeds

Hi, I am starting to think that my car is developing a fault and was interested in other Tiptronic views on the below: When going up a slight gradient at about 2k rpm the engine feels as though it is pulling slightly. It is hard to explain, but I can see the rev needle move about 1/2 notches every second, almost in time. It feels as if the engine is about to stall and the engine management is giving the engine a little boost to prevent it happening. That's really the only way to describe it. It happens in all the gears, but it's most obvious in 4th and 5th, around 2000rpm, sometimes 1500rpm. If it was a manual, I'd put it down to being in too lower gear, but it's in D and is selecting the gears itself. If I manually drop down a gear when this is happening, it doesn't do it any more. I'm wondering what the matter is, because it doesn't do it all the time and it's going to be a sod for the OPC to try and recreate the problem. No OBC messages appear on the display and apart from that, it seems fine. I'm wondering if it's the coil pack or MAF that might be on the way out, but it pulls very cleanly through the rev range without a problem. I also noticed that when I'm driving on a flat, if I keep the accelerator in the same position, again, maybe it's my imagination, but I'm sure the needle sometimes moves, even though I'm being really, really careful to keep the engine revs steady on a very smooth road. Cheers.

Sounds to me like the initial stages of a MAFS fault. MAFS will have a trouble code but will not bring on the EML (engine management light)

Try calling your favorite Indy - they'll be more patient, and a lot cheaper, than OPC Ray

Cheers Lloyd, I'll miss your input when you sell your car. I'm getting the rear brakes and discs replaced shortly, so I'll get them to look at the MAF then. Ray, my car is under OPC warranty, so it should be done FoC (hopefully). My local independent has become a OPSC and moved location to make it more awkward to get to (and they also cannot issue me with a warranty), so although I get preferential rates, the journey and cost isn't worth the saving. Cheers.

My pleasure, may have the car a while yet.. won't be giving it away! Was think about your issue today, try resetting your throttle body, simple to do. Turn on ignition until all lights come on but don't start the engine or touch any pedals. Leave like this for minimum 60 secs, go to rear of car and you should hear what sounds like a multichanger swapping discs, it is the thottle body re-adapting. After over 1 minute is up turn ign completely off for 10 seconds then fire her up and go for a drive. If still no better try driving car with mafs disconnected, don't worry, it won't put the EML on. If you feel improvement you can be pretty sure it is a mafs fault but to be 100% it needs the values read on PIWIS or Durametric code reader.

The procedure also resets the DME adaption values. As you run the car, the DME adapts the fuelling to compensate for fuel quality. Restoring the settings to the factory default (just after a fill-up with V-Power!) will usually give a perceptible improvement in performance. It only works on cars with eGas - for early 3.4s you need to disconnect the battery.

Hi Richard, just to confirm 'early' is this identified by early cars have cable throttle body and the later have fly-by-wire? I am guessing the change point to be somewhere around T - V reg?

Model Year 98 and 99 Carrera 2's (those built up to August 99), and Mk1 GT3's have mechanical throttle, everything else has 'eGas' electronic throttle. An easy way to check is to look at the options sticker - M620 is eGas.

It could be just the cars learned you're style of driving ? Mines an early tip like yours, and it only has a few driving programmes in the tip ECU, the later ones have a couple of hundred I beleive. I think they adopt the one to your style of driving, so if you're 'bimbling' it's slower to change gear. Give it a spirited run for a few miles, and it should adopt the sportier shift until you start driving slower again.

I take the number of driving programmes back, just seen your's is a 2003 The fact that it will adopt a slower change still stands though.

I have the exact same problem in my MY2000 C4 Tip, and have had for a couple of years. Replacing the MAF sensor as suggested earlier did help a little - do this if you're having trouble starting from cold, or the engine runs very rich at start up. I've had the "learning codes" reset a couple of times to no avail too. A while ago Jim (Vice Chairman of TIPEC) was telling me that these ZF boxes when installed on other cars (Jags I think) used to experience an intermittent failure of a solenoid that was used to control the internal oil pressure (which in turn is a factor in causing a gear change). The solenoid (which is serviceable) would be "sticky" and would cause the box not to shift down when it wanted to. That sounded a lot like the problem I have. However even a gearbox specialist I took the car to didn't corroborate that (I didn't feed him the story - wanted to see if the guy would suggest it). On the positive side, it can't be a major problem or the box would have lunched itself long ago. I've done 12000 miles over two years and the problem has never got worse. Would be interested to hear if you learn any more information.

Hi, Thanks, I tried to resetting the throttle (always have used super unleaded, although not always V-Power) and I think this has helped the problem (but I won't know until I drive home from work, because it seems to happen on a particular stretch of the A3, uphill at 50mph). Thanks for suggesting about the the gearbox adapting to your driving, I was aware of that, but that isn't the problem. It's more like what the previous poster was suggesting about it not switching down when perhaps it should, although my one has the more modern Tip gearbox (Mercedes, I think. I thought the ZF was on the earlier models?). It seems to happen around 2,000rpm and you definitely see the needle jump about within one space (500rpm, I think). Odd.

I wonder if it might be the Variocam. The switching point is about 1500rpm (hot). Perhaps it is changing the cam timing, the revs drop (maybe because of the slope), and the timing is changing back again. I get a similar slight fluctuation at a constant 15-1600 rpm in a high gear (30mph-ish) on the flat. The revs don't move up and down as much as yours, but you can just about hear the engine note changing and see the rev counter moving if you really concentrate. It's one of those things that once you notice you can't ignore. Never got it with the 3.4 C2 (ZF). Just a thought - might be b*ll*cks - and probably is. :dont know:

Hi all, Mine does exactly the same thing at 2000rpm. I am almost convinced it is the MAFS but want to disconnect it and see if there is any change before I book it in to be replaced. Alternatively, if this is an easy job I would be happy to do it myself. Can anyone advise. I have had the car serviced at Byfleet since the problem has been evident and no diagnostic codes were displayed when it was plugged in. My car is an early 2002 model and despite the fact this definitely isn't a major problem it is still driving me mad.