2008 Tahoe 5.3 Rough Idle

I have 2008 Chevy Tahoe with the 5.3 flex. It as about 175,000 miles on it.

The problem that i'm having is rough idle. It starts fine, doesn't stall, seems to run fine at higher RPM.

Some additional info:
- no codes
- new plugs and wires (I know... probably didn't need them)
- Checked the resistance of each fuel injector and they were good - also I could hear each injector pulse with a dr. type scope.
- Fuel trims look good:
-- STFT Bank 1 = 0,
-- LTFT Bank 1 = 0,
-- STFT Bank 2 = -2,
-- LTFT Bank 2 = -3.1

There are no missfires

Fuel pressure (according to scan data) is 43.5psi running (spec is 50-60)

Mass Airflow Sensor = 0.01 lb/s

Throttle Position = 19.2%

I am:
- considering cleaning the throttle body.
- concerned about the fuel pressure (but need to do more research)
- wondering if it could be a mechanical issue and that I should do a compression check.

Thoughts?

Umm that lbs/min is low on ur maf.... it should be reading .7 lb/min or approx 5grams/sec since u have a 5 liter engine... this .01 lb/min is way low.... clean the mass air flow sensor and check power and ground to the sensor... also this 19% on the tps is that idle foot of the pedal??? If it is thats too high in my opinion

My maf reading was in lb/s not lb/min so if converted to lb/min it equals = 0.6 or 4.5 g/s which still is lower than .7 but not as far off.

The tps reading was at idle, so I think i'm going to look at that some more.

Thanks

Ok your right im sorry i didnt catch the s... i thought i saw an m

That is still a little low on the maf ,and tps is way high clean the maf and the throttle body

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Was that Throttle Position reading Relative of Absolute?

I agree, the 4.5 g/s reading is too low for this engine at idle. I'd suspect a vacuum leak, but the trims are excellent. :blink: Whats the MAP reading during the rough idle and 4.5 g/s MAF reading?