First, thanks for coming in here to help me with mycar problem. Did a bit of searching but nothing really related to what i have going on with my car. As for the car, it's a 1999 A4 2.8L V6 Quattro Auto. My car idle rough/shakes when it idle at 800 rpm but if i raise it up to 1k rpm it smooth out. My car has also lost some low end when driving. Now to the DTC.

My DTC is P1392 which is CPS sensor bank 2 Open circ/short to B+. I'm thinking that's what's causing the rough idle as well.

Here's what i did, I replace the cps sensor with a new one hoping that wouldsolve theproblem. Nope, thecode came back so i switch the two cps sensors and still the same code came back.

voltage between terminal 1 and 3 is 11.0v which is in spec
ohm test all three wires from the connector to the ecm and all of them are .4 ohms, so it's within spec as well
cross check wires for short and found none

So now i'm here seeing if anyone can point me on the right direction as what to do next to remove that DTC. Thanks for looking.

 

would anything mechanical cause the sensor to not read right?

thought about running new wires, butthe old wires testedfine. Only thing left to do is fine a used ecu somewhere and try that out.

 

had a similar problem with my 96 2.8 was rough idol as well.. i tried plugs, wires,coil packs, o2 sensors , mass air sensors, etc turned out the throttle body was dirty....like a 4 dollar job if you go buy the can of cleaner

 

was it easy to get at the throttle body?

 

new ecu and wiring and the problem is still there... there most be someone on here who knows...

 

yangtech, the throttle body is visible upon opening your engine. There's five screws that hold it in, which you can easily get to. Take it out, and be gently scrub away the dirt and grease with some throttle body cleaner. I used CNC on mine, and it cut through the grease as soon as I sprayed it in.

 

well on the 1.8 the throttle body is just sitting right there, but the 2.8 looks like a pain to get at.

 

If you have a vag-com, check your ignition angle at idle and your throttle angle at idle. If they're not within the specified range, clean your TB.

 

no vag-com for me but it idle great until i got the DTC, which i'm sure is causing the idle problem.