We have a 2002 Jetta that developed a number of issues at 57K miles. I thought I'd review the history to see if it might help someone else with the same problems.
It started with poor idle and stalling, once it died on the interstate, in traffic.
I got a cable and started looking at the diags and found:
Mass Air Flow Sensor (G70): Signal too Low
Fuel Trim: Bank 1 (Add): System too Lean
and multiple misfires on all cyls.
I cleaned the MAF and it ran a little better. I let the daughter take the car.
Car still had poor idle. Checked coil packs and found broken wires. Tried to tape and seal wires but still had misfire and poor idle.
Changed temp sensor since it was a $25 parts. No joy there.
Ordered new coil packs, bought the Hitachi ones and installed them. Car still the same. Added new plugs as well, used NGRs.
Cleaned the throttle body. Idle stabliized when warm. ran pretty good at this point. CEL still came on. Getting Fuel Trim: Bank 1 (Add): System too Lean and multiple misfires.
Changed O2 sensor, and the`Bank 1 System too lean' error code is no longer.
Also, at this point, I pulled the wiring harness for the coil packs apart, slipped two layers of heat shrink over the broken leads and sealed the whole harness back up. Still have multiple misfires. I'm sure this isn't the problem. I used heatshrink the whole length of the wires because I was concerned with further cracking. Also used tape, of course.
So, I feel I should have cleaned the TB and MAF first, changed the plugs and gone from there. These were the cheapest things to do and resulted in some good results. Then I'd have done the temp sensor then O2 sensor. I would have finished with the coil packs.
I now just have multiple misfires on all cyls and a CEL. I thinking of looking at TSB 0106-26 that deals with misfire on 1.8t engines.
Since I no longer have the fuel trim: system too lean error, I'm thinking I do not have a vac leak.
An other ideas?
Modified by 2002JettaMike at 2:24 PM 4-20-2008
Modified by 2002JettaMike at 2:27 PM 4-20-2008