Slight hesitation on low rpms

[Thklinge]

Got an '02 Turbo with 67k miles on it, upgraded turbos, new motorsport DVs, chip, 100 cell Milltek exhaust, 5 bar FPR, and so on. Pulls strongly, no problems at WOT or spirited driving at higher rpms.

The problem is a slight hesitation when getting back on the throttle at low rpms that's been getting progressively worse. Most noticeable in 1st and 2nd gear. I apply a bit more throttle to accelerate but the car seems to cut for half a second before pulling its **** together and giving me some power. It happens at low rpms, so I guess its not boost related. As it happens with the clutch engaged I guess it isn't driveline-related. Happens both with engine hot and cold. Tried disconnecting the MAF without change. No CEL, no errors in Durametric. New plugs. The oil pressure dips at the same time as the car hesitates, which could suggest something variocam-related, but I tried the drivelinks activations for the variocam system and the rpms changed for all of them. Probably not a fail-safe way to test the system, but at least it responds. Can the dip in oil pressure be indicative of something else?

The serpentine belt squeals when wet. I replaced it and it still squeals. Not sure if that is related.

I sometimes get an PSM/ABS-error, usually just while coasting. They disappear the next time I start the car and drive away. Could indicate a bad MAF or bad connection, but the hesitation is still there even with the MAF disconnected so it probably isn't related to the hesitation?

Searching the issue yields a lot of answers like MAF, vacuum leak, boost leak, bad plugs, broken variocam solenoid brackets, loose plugs, bad coilpacks, dirty trottlebody, worn clutch, worn egas cogwheels, dirty egas potentiometer, and so on... So I'm looking for some hints before I start to throw money at the problem. Although I did buy six new coilpacks so I have started...

[Dus10R]

Who's chip? Or is it flash loaded? If flashed have you or can you flash it back to oem? Have you data logged it to see what the AFR's are doing? Mod'd turbos can be finicky to work out bugs. Does it still have the stock boost controller? I see you mentioned throttle body, did you take it out and clean it? ( it usually causes rough idle and stalls though, not hesitation). Are the waste gates synch'd to open at the same time? When you say modified turbos are you talking about a K24/18 upgrade or something else? Stock intake or after-market?

[Thklinge]

Flash from EPL. Tried stock, same hesitation. Haven't checked AFR, what should I be looking for / what parameters to log?

Not sure about boost control, car was tuned before I bought it. Trottle body was cleaned (although not very dirty) without removing it from the car. Removing it, cleaning it even more, and checking the egas electronics/mechanics is on the todo-list. Not sure about the wastegates either. Turbos have a larger compressor side as far as I know.

Car was running great when I got it about a year ago. It's gotten progressively worse unless my mind plays tricks on me. It most definitely wasn't hesitating it when I got it.

[Thklinge]

Did a thorough test with Durametric today and found code 4201 on the ABS system (front right sensor - signal implausible). Guess the sensor is dirty or bad, and that explains the ABS/PSM errors.

Still nowhere closer to an solution for the hesitation though. Any thoughts?

[Dus10R]

Reach out to Markski at 911tuning.com. That dude knows more about modified 996 Turbos than anyone I know of. He's super cool and very helpful, even if you don't have their products. info@911tuning.com ive been out of the 996 Turbo tuning world for. 2 years now and have forgotten most of the tips and tricks and things to check. Markski can tell you exactly what parameters to data log and how to do it.

A hesitation at that low of rpm almost sounds like its getting too much fuel, or not enough. But in reality it could be numerous items with a tuned car so data logging it is key, hopefully it does it during a data log so you can see what its doing.