1994 Volkswagen Corrado Irratic reving when cold

Hi Frankos76,

Thank you for the donation.

This phenomenon is commonly known as "surging" and is happening because of erratic idling.

If the CEL is not showing, then you either have a vacumn leaks between MAF and throttle body or the MAF sensor and/or throttle body is dirty and requires cleaning.

Is the replacement part brand new or used?

Thanks for reply, there is no check engine light on my car, i didn`t think? the amf air mass flow meter is new. also the car has lost some water, down to half inch below min water level, i always keep the levels up, is this to do with the same problem

Hi,

Yes, low coolant level would cause surging as some of the components requires coolant to run through to provide the correct operations and lack of coolant wuld cause incorrect signals thus the surging.

If coolant is depleting, get a pressure test done to see where the leakages is and rectify it. Failure to do so can have dire consequences if engine were to overheat.

Does the problem occurs immediately after topping up of coolant?

Hi, i found a radiator o ring broken which caused the leak and now have topped up the water, the car still reving whether the engine is warm or cold. I have got a diagnostic meter which says 00525 - o2 sensor low voltage, 00561 - mixture adjust control, 00537 - oxygen sensor control and 00513 - engine speed sensor idle low, high or malfunctioning. Does this info help? cheers

Hi Frank, Yes, the codes sure would be of use. I have the descriptions here but not all these might be the cause so to be more accurate, did you erase the codes? If not, try erasing them and recheck codes again to see if all are repeated. 00513 (2111) Engine Speed Sensor Open Circuit Or Loose Or Faulty Sensor. 00525 (2342) Oxygen Sensor Open/Short Circuit To Ground Or Battery Voltage 00537 (2341) Oxygen Sensor Regulation Control Limit Exceeded Or Not Reached All the codes retrieved, except 00525, does not seems to be the cause of the problem but rather the problem is causing the codes to appear. If after erasing the codes and they all do not appear while the engine is still surging, check for a stuck or faulty Intake Speed Control valve, item # 9 in diagram or a dirty Mass Air Flow sensor, item # 2. Using carb cleaner to clean both items might help.

00561 (2413) Fuel Mixture Adaptation Control Limit Exceeded Or Not Reached

Hi, i have erased the codes, the car seemed fine to drive for 5 miles but when i got home the codes had come back. i have removed the amf sensor and intake air control and pipes and cleaned with carb cleaner, also cleaned the throttle body. no change, could the prob be the egr valve? thanks

Does all the previous codes comes on and in the same order of occurrence?

EGR would not cause surging. It would cause hesitation or lack of power.

hi, all the codes appeared again except 00525, the order was 00561, 00537, 00513. Then after erasing them for a second time they all came up, 00525, 00561, 00537, 00513. Would it be worth getting a new lambda sensor? cheers

Seems the Lamda sensor is out and and I would agree with your suggestion of replacing it.

It would cause 00561 to appear.