What can cause an 05' gmc sierra 5.3L to idle rough and almost cut out but when drivin ts good and full of power?

Answer 1

I have been studying this problem for weeks for my 2001 Tahoe. Idle issues seem to be a common problem for the 5.3L, but most of them are quick and inexpensive.

Here is what I would recommend checking:

1. Remove the intake cover and clean the throttle body with carb/choke cleaner.

2. Replace the spark plugs....(THEY NEED TO BE AC DELCO IRIDIUM) The 5.3L is VERY particular about this!! I have been searching forums etc. and many of us have been using the NGK Iridium and solved the prob by switching back to the AC Delco plugs and wires. Some have said the Delcos are made by NGK,which may or may not be true, but they are not the same plug. NGK is actually slightly lighter weight and slightly shorter. (Don't believe me?.... Check with your auto parts store and compare them side by side) DO NOT gap the plugs. You will ruin them and the pre gap of .40 is the new standard (not .60).

3. Remove and clean the EGR valve. There is only 2 bolts and a electrical connection. (Recommended every 60K miles)

4. Check the fuel pressure regulator. Remove the vacuum line while the engine is running and wait. If fuel starts leaking out it will need replaced. Be patient.. small leaks can take a couple mins to show up.

Still having probs? Check for an idle air control valve located in the throttle body. Remove and clean off the carbon. My Tahoe has one but I am not so sure about an 05.. I think they were removed from the newer models.

After that it gets more expensive... it could be a sign that the fuel pump is going or worse the intake gasket is failing. Best of luck to you.