Rough idle, check engine light
 

My check engine light came on and the truck started idling rough. On my way to lunch today it actually died at a stop light.

I had the codes read and it came back with a 171 & 174 indicating a lean condition.

Any ideas what could be wrong?

Unmetered air leak, dirty MAF sensor, clogged injectors, clogged fuel filter, low fuel pressure? Since the lean indication is on both banks 1 & 2, I would suspect that it is probably not a failed O2 sensor, although it is still possible that they both failed.

Hey Bob,

I have a CEL reading the same codes. I've changed sparkplugs and put a new MAF on and still the same codes. Can an iol change place check my fuel pressure? or any other ideas on what I can do?

With a lean A/F mixture problem, there are so many possibilities. Of course, I would do the cheap or free stuff first. Make sure all vacuum lines are plugged in and not leaking. Check the security of the clamps on the intake tube and be sure the PCV closure tube is plugged in correctly. Then make sure the throttle body bolts and the intake manifold bolts are snugged up (but don't overtighten them). Add a can of fuel injector cleaner to a full tank of fuel and run it through it. I would suggest cleaning the MAF if you hadn't already said that you swapped it out.

Have the fuel pressure checked - you could have a weak fuel pump, plugged fuel filter or a bad pressure regulator. I would guess that an oil change place would not have the special fuel pressure gauge for that. A dealer, or possibly an independent, would have it, though.

Tired or contaminated O2 sensors can cause this by misreading the mixture. There's no easy home test on these except to swap them out.

I have this exact same problem and was ab00t to ask the same thing. WOW! I have also noticed that I have been getting really shizz, worse than normal, gas mileage also.

I figured out the problem. There is a vent on the back of the drivers side valve cover that I believe is the PCV valve. Two tubes come off of it and route around the back of the engine and connects to the throttle body on the passenger side. The larger of the two tubes has a rubber 90 degree bend in it right before it enters the throttle body. This rubber piece had a hole in it. It looks like it was eaten through from the inside. I replaced it with a cut down piece of heater hose with a 90 degree bend that was the same diameter at the original piece. I started it up and it idled beautifully. After resetting the computer, the check engine light went away and hasn't returned.

I have the same problem, but no CEL. I've replaced the IAC and the same piece of tubing as Snowgoak, but no difference. My symptoms seem to only arise after driving for an extended period (20 minutes or more), usually when I enter the parking garage at work. I stop, shift into reverse, and when I back into my parking space it feels as if the truck is going to die. The tach will drop below 500 RPM, then bounce up to about 1200. When I am driving it is fine, although the idle is high (around 1200 RPM) until the engine is up to temp. Any suggestions before a costly trip to the dealer?