Felix

Trying to get my mind away from tb993tt's "new" car and all those fab pictures...

My car has a slight surge at steady throttle, most noticeable between perhaps 2000 and 4000 rpm at most road speeds. It feels like someone is making very small throttle adjustments in a fairly rythmic manner. The MAF is about 3 years old and plugs about a year. No codes in the ECU. Any suggestions on where to look for issues?

Spartan

hmmm small boost leak maybe? If that was the case you notice something under WOT. Also give the Maf a quick clean and see if the problem persisits. Bosch Mafs should be considered a long term consumable in any car and it may be time for a new one. Does your boost do anything funny? I've had N75's got bad before

Being that there are no codes thats where I would start. Good luck!

geolab

ISV mate ISV, Idle Speed Valve
Need to spray a spray of WD40 inside, and you're good to go,
read on normal aspirated forum, classic issue

Felix

OK, I spoke too soon. There's no CEL but there are codes as follows:

Fault Number:16 - P0133
Description:Sensor ageing ahead of cat.
Repair Infomation:conv. conv. cylinder (1-3)

Fault Number:17 - P0139
Description:Sensor ageing behind cat.
Repair Infomation:conv. cylinder (1-3)

Fault Number:22 - P0153
Description:Sensor ageing ahead of cat.
Repair Infomation:conv. cylinder (4-6)

Fault Number:23 - P0159
Description:Sensor ageing behind cat.
Repair Infomation:conv. cylinder (4-6)

Fault Number:12 - P0136
Description:O2 sensor behind cat. conv.
Repair Infomation:Cylinder (1-3)

Fault Number:20 - P0156
Description:O2 sensor behind cat. conv.
Repair Infomation:Cylinder (1-3)

So the ECU and my O2 sensors aren't getting along very well! The post-cat O2 sensors are hanging out in the breeze as I still have two wideband lambda sensors installed as part of my datalogging fun and games. And the pre-cat O2 sensors are only about 2 years old. I have cleared the codes and will take the car for a run.

Felix

OK, codes cleared and not reappeared in 50 miles and no difference in the car's running.

Hwyranger

My car did that, slight surge at steady throttle while driving on the freeway. Spark plugs were the culprit for me.