So I went to the track for the first time with my new to me 99 Z28 A4. It did not turn the results it should have. My fastest time of the day was a 14.69 at 97.5 mph with a 2.19 60'. The car is completely stock except for a lid and Corsa catback. The car IMO should have gone in the 13.40 - 13.60 range from what I have seen and should have trapped probably 103 - 106 somewhere. The car does not run badly at all and the only codes I get from time to time is PO137 and PO157 which are the 2 after cat 02 sensors. Help me diagnose why the car is running poorly performance wise.

Here are some things I have done so far and how they have helped. I have already pulled the MAF and cleaned it using some electronics cleaner. I did this because I was reading about the PO137 and PO157 codes and I read that sometimes the MAF can cause these codes to be thrown. Since I have cleaned the MAF I have not gotten any codes at all and it should have thrown the code by now, because I have been getting on the car pretty good. I also have replaced the fuel filter and checked the plugs and plug wires. The Plugs did not look horrible but could stand to be changed, they were the NGK iridium plugs. I also pulled a plug wire and the measured ohms through the wire was 1367 Ohms. From what I have seen on the boards here that is pretty high. I have some new plugs and plug wires that are going on the car tomorrow morning first thing.

Now just from doing the fuel filter and 1 plug(the one I pulled to have a look at) the car already feels stronger. Now from a dead stop if I stab the throttle it will spin the tires pretty much through entire first gear, it would never spin the tires at all before. I am going to do the rest of the plugs and wires but is there anything else you guys can think of that I should change out or check that might affect the car performance wise? Like I said the car runs fine, no sputtering or missing or anything but the power is just low.

Also the car does have 120k miles on it and its the stock 4L60E. It seems to shift fine and feel fine but I don't really know if the tranny is slipping or not. Is there anyway to test the tranny to see if it is slipping?

Any help is appreciated. Thanks

 

Sounds like you already have the first few things set to be done or have done already. I'd get the rest of your plugs/wires replaced then go from there.

 

you might wanna do a compression test on the engine to to test the mechianil integrity of the engine its self.