Have and 03 Deville 110+ k miles. Getting codes P0171 and P0174. Checked hoses and sprayed carb cleaner all around and didn't get a change in idle. Cleaned MAF sensor as well and still no change. Hooked up a scanner and is running lean at idle but good at acceleration. Anyone deal with this before?
Running Lean. Where to look?
- Thread starter Dehaka
- Start date
Could it be the oxygen sensor providing poor information?
Have you tried a good fuel system cleaner to clean any injectors that may be performing poorly and maybe the oxygen sensors too?
Have you tried a good fuel system cleaner to clean any injectors that may be performing poorly and maybe the oxygen sensors too?
GM had intake manifold gasket issues and changed to a new gasket type around that time frame. I would focus around there for vacuum leaks. Are any intake manifold bolts loose? PCV connections and hoses?
I only run chevron gas which has techron and I use lucas fuel system treatment every 3 k oil change.....
Everything seems snug.
The scantool only shows lean codes but i just checked the onboard diagnositc and also got a p 1617 code as well.
Yeah a buddy of mine thinks it could be an intake gasket leak. Would that show up if I smoke tested the engine?
Agreed w/ previous comments about a vacuum leak somewhere. At idle vacuum is typically the highest unless you're coasting/braking. If the engine is acting funky at idle but alright on accel, vacuum leak is a great first assumption.
I'll second fuel injectors dirty or bad O2 sensors
I'd check for vacuum leaks and consider smoke testing it if I can't find any.
would s smoke test reveal an intake leak?
Yes.
yes, it is the best way, you can also try propane instead of carb cleaner, it is safer
If fuel trims get better at higher rpms, that usually indicates a vacuum leak. I would smoke the intake and see if you see any smoke coming out anywhere.
You have to smoke test to diagnose this one. Smoke will find vac leaks that spraying carb cleaner will not find. I have seen this happen on a Northstar where the evap purge solenoid was the culprit allowing too much in but not enough to set a code. Another thing- cleaning the MAF was a good idea but really that is a 50/50 shot that only helps if it was dirty. I would still have the MAF on my suspect list. Go head and unplug the MAF and drive the car and see if the lean codes go away. Sure you will get MAF codes and that is ok - we are letting the car run off the backup MAP sensor. If the codes don't come back - plug the MAF back in and see if the codes do come back - if so - MAF is bad.
Good job!
Over time this happens to a lot of vehicles...
