In the past month, I've seen 3 Cruzes with the same problem. All had the LUW 1.8 engine and from 800 to 1200 miles. They come in with a complaint of MIL on, rough running, and black smoke out exhaust. They always set a P0101 and sometimes rich and/or misfire codes.

In each case, if you graph MAF on GDS2 between 1.0 and 4.0 gps, at idle with all accessories off, the MAF will usually run about 3.2 - 3.8 gps with a constant .5 gps change. The graph almost looks like a perfect sine wave. The MAF is over-reporting air flow to the ECM.

If you remove the top of the air filter box, there is a short piece of tubing with a screen on the end made out of plastic. This acts as an air flow straightener/diffuser for the MAF. This tubing falls out of the air box cover and lies on top of the air filter. This exposes the MAF to turbulant air flow. The retention on this tube is poor and I have been cementing them in place with hot melt adhesive. After the repair, the MAF idles at about 2.4 - 2.5 gps with almost a straight line graph.

If you're a G.M. tech, keep an eye out for this.

James from Florida