Car will hiccup(rather abruptly) during cold acceleration and occasionally stall. No check engine lights. This is intermittent and the dealer has not been able to reproduce it on two separate occasions. I have also logged a complaint to GM. The answer is, it has to get more consistent for us to diagnose or I have to leave the car there for a long duration. They won't pay for a rental car unless they know the fix is going to be covered under the power train warranty. I have 60K on the car and its out of the bumper to bumper warranty. This morning I logged some ODB II data of the event. I am hoping someone in this forum is more familiar than I am at understanding this and can divine the magic bullet from this data.

https://docs.google.com/open?id=0B_1...UR2RW5BTVEyWE0

you have something that shows more values like temp sensor, maf, fuel trims? fuel pressure is weird i dont have the specs but normally doesnt swing that much. i dont think the car has a filter but i wonder if there isnt something in the pickup screen for the pump, i wouldnt think it should get that low. what engine is it?

Air fuel ratios look good, except I question the accuracy of the readings unless you have a wide band O2 sensor. The graphs superimposed on the data unfortunately hide the most valuable information; fuel pressure. I would suspect:

• fuel filter
• fuel pressure regulator
• contamination in tank blocking fuel pick up screen

Thanks to both of you for looking. I had intended to just post the sheet in this forum but it only lets you attache images so I had to use this google docs link. You can get the entire sheet if you are willing by selecting download under the file menu on the link. There is alot more data from the senor in the sheet that google is not displaying. Thanks for checking it out.

Sorry I missed your question before. Its the 4cyl direct injected engine.

does it have a access door for the fuel sending unit? if so i would take it out and inspect it.

not sure....I will look when I get home....is that something I would have to drain the gas tank before removal?

On thing I was not clear on. This has never happened on a warm engine. First thing in the morning usually in front of my house, clear itself after 500 feet or so and runs fine the rest of the day.

Justin is asking if there is a access panel that lets you get at the fuel pump without dropping the tank. If you have one it may be under the rear seat.

In that case the solution would be to never park your car closer than 500 feet from your house.

Forgive me, its Friday.