Golf mk4 1.6 AKL lacking power

[Eyjok76]

Hello everyone.

I have a problem with my 1.6 Golf year 2000. It lacks power and hesitates when cold but gets little better when hot. When running hot it drives better but it still hesitates and a occasional misfire bang. Idle is also erratic and bad.

OBD gives me codes 525 and 537.

The engine has new piston rings changed 2 years ago and it does not burn oil. I measured the fuel pressure and it was 2.5 bar + 0.5 when I removed the vaccum line. All injectors are working also and no vaccum leaks are present.

I have installed new: Spark plugs, fuel filter, Camshaft sensor, crankshaft sensor, o2 sensor, temperature sensor, HT pack and sparkplugwires and borrowed MAF sensor from a fully functioning car.

Now I am not sure what the next step is, any ideas?

[Crasher]

00525 - Oxygen (Lambda) Sensor (G39)
00537 - Lambda (Oxygen Sensor) Regulation

I would say you have a mixture control problem, knowing the AKL I would expect it to be an air leak in the plastic pipe after the air mass meter and before the throttle body.

[Eyjok76]

Thanks for your reply Crasher, but I forgot to mention in my post I replaced the plastic hose and also used gasket silicone so no air could slip in.
Are there any other known culprits you can think of?

[Crasher]

The sensor itself could be at fault as could the air mass meter, you need to do some diagnostics on a 4 gas exhaust analysis in Measuring Blocks 020 and 099 with the lambda control turned off and in Basic Setting 099 with the lambda control turned off (if that in in your cars ECU software version). Code 00537 has two variations, upper or lower limit exceeded; it would help to know which your car was producing.

[Eyjok76]

OK. Now I have replaced the the lambda sensor and get "no codes found". Still it behaves in the same manner, a little better tough.
The engine reponds sluggeshly to sudden acceleration and occasionally bangs when it´s cold.

I have replaced and inspected the intake manifold and probable false air leakage, but with no luck.

Any suggestions are welcomed

[Eyjok76]

Problem solved!!!

My "new" spark were the culprit, which I replaced 18months and 15.000 km ago. Replaced Brisk spark plugs with Champion spark plugs. Will never buy Brisk again.

[Crasher]

Been there, done that got the T shirt, video and the annual. Stick to NGK plugs as a rule or Beru in certain applications, even Bosch give me trouble. I would not touch Champion with yours.....