RJ11

I have a 2001 A4 1.8t (B5). I'm at a little over 120k miles on it. In the past few months I've replaced both O2 sensors, the smog pump, MAF sensor, vacuum lines, DV, EGR valve, spark plugs, ignition coils, valve cover gasket, and last year I had a new catback exhaust put in.

The other day I noticed that when starting cold, the car would idle all over the place and misfire on all cylinders (sometimes going as low as 400 rpm before stalling out). I took it to my mechanic, and he replaced the fuel pump and two breather hoses. When I picked it up, it worked fine. Today, the CEL came on again while driving to work, and the codes are P1128 and P1136. I clear them, restart the car, and the idle is very rough (misfires are detected on all cylinders, but the CEL did not immediately come back on).

What could the problem possibly be at this point?

RJ11

I just removed the throttle body and gave it a thorough cleaning. It wasn't very dirty. When I cleared the codes and started the car, same problem: misfiring on all cylinders (P0300-P0304), P1128, and P1136, just as before.

5v/cyl

Have you replaced the CTS and fuel filter?

Both codes are lean run and generally a MAF or vac leak issue. Double check both. Has your mechanic used a VAG-COM on it? If not get one and start looking at what the sensors are telling the engine.

RJ11

I replaced the CTS last year when the code came up (yes, I've got a VAG-COM). Haven't replaced the fuel filter (was surprised the mechanic didn't do it when he did the pump), but would that explain the engine running fine at idle when in limp mode?

It's definitely running lean, the codes are P0300-0304, P1128, and P1136.

Gustafdgm

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Gustafdgm

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