adam02gt

iTrader: (1)

I recently put headers on my 98 z28 a4. The car ran fine for a day or 2 then started running poorly. I logged the car with hptuners at a friends house and determined that the o2's were bad. Well on the way home that day one of the wires got cut on the passenger o2 and popped the eng. sensor fuse, I replaced the o2's and the fuse and logged it again same issue still there. Changed the maf out and it didn't really help at all. The problem I'm having is the o2's will read 800-900 mV at WOT but at idle the passenger side will stay around 450 mV and the driver side stays under 100 mV. They should be bouncing around. Now the car loads up with fuel and idles rough and until you go over about half throttle it stumbles and doesn't want to go. I've looked at wiring and don't see any problems. Any thoughts?

adam02gt

iTrader: (1)

No one has any ideas?

adam02gt

iTrader: (1)

bump...come on I can't be the only one thats ever had this problem

almostfast

you still have all 4 o2's? they are all broken?

almostfast

an HPt log would be helpful too if you could post one.

got-a-ls1

iTrader: (12)

I know when i just installed my headers the passenger side o2 would go full rich and the car would stumble, not accelerate and just plain sound like ****. Well i figured there was an issue with the o2 or the soldered extensions... The car would explode with power as soon as it would hit Power enrichment so i new it was the o2's before i even scanned it.. It would really only have the problem for the first half hour id drive it either from the o2 heating up fully or the fuel trims helping out.. Anyway i reset the fuel trims and drove around for a day or so, it did it a couple times and then seems to have learned itself out... hasnt done it since. When you move the o2's that much further downstream the exhaust gas, especially through headers, lose a lot of heat and may screw with the sensors... driver side o2 was fine so maybe the passenger side's heater is just wearing out. anyway something to try..

also make sure the car is entering into to closed loop when its stumbling... or you can also try to force open loop and see if the car runs better. Thats how i got my car home the first time... it would hardly run until i went into vcm controls and forced open loop. it ran beautifully in open loop....

john.s

iTrader: (6)

Ya the o2's are brand new so. I'm gonna try unplugging the front o2's and force it to stay in open loop and see what it does-Adam....,

adam02gt

iTrader: (1)

Just unplugged the front o2's and the car runs fine.....So it's definately a closed loop problem....I wonder if the o2's aren't getting heated up enough to read? How would you fix that?