2012 Sierra Idle

[Bad Bowtie2]

My 107K mile 2012 GMC Sierra 5.3L 4x2 is starting to have a MILDLY rough idle at times. Cold and/or hot motor.

 

In the last 2 weeks she is now starting to "surge" at times when stopped at a red light. Foot on the brake, in gear, like you reach over and tap the gas pedal for a second.

 

I have no "SES" light either.

 

Original fuel pump. Old AFM lifters & cam were replaced at 85K, GM Tech used GMPP performance roller lifters & slid a new GM 6.2L cam inside (non-AFM of course).

 

New GM spark plugs & wires at 85k, new GM O2 sensors (all 4) at 95K. Just for maintenance reasons. 

 

I do my own oil changes at every 6K, and add a bottle on Chevron with Techron fuel treatment at this time too.

 

I only run NAME BRAND fuels in my truck too- No off brand stuff.

 

Any known issues or clues my GM brethren??

Edited August 18, 2019 by Bad Bowtie2
Grammar

[dtnel78]

Have you had the fuel system cleaned by something other than the bottle treatment stuff you put in the fuel tank?

Also depending on where you live you'd be surprised where fuel comes from.

There's a fuel depot here in town and that's where all the local fuel companies get their fuel. Generally what happens after that is each company may put a 5gal bottle or less into the tankful they deliver to the station or stations they deliver to.

The big name brands have their own trucks that deliver their fuel from the same "rack" that the rest of them have a fuel delivery company deliver their fuel from.

I drove over the road for 13 1/2 yrs from 97 to 2010 and that's the way alot of their gas station / companies get their fuel / gas, from a local hauler or their own truck at the nearest fuel depot.

You'd be surprised how many other companies are in line getting their fuel from where yours comes from. When I say line, yes they get a lines generally as fuel rolls in cycles based on demand. More people buying then more trucks in line at the rack to load to your local near or far stations as one rack can serve stations up to a few hundred miles away.

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[Bad Bowtie2]

No, I have never had any other fuel induction service performed.

 

I just cleaned my Mass Airflow Sensor & I am cleaning the throttle body today too...

(cheep trys)

Edited August 17, 2019 by Bad Bowtie2

[dtnel78]

also I meant to say if you find somebody locally that can do a Fuel Injection Service cleaning that may help if you haven't did that since you've owned the vehicle. They cut the power to the fuel pump and if you have a return line they also make sure that's blocked off and then they hook a line in with a container that's pressurized and make sure that it's at the appropriate pressure an ad a fuel injection cleaning solution then start the vehicle and let it run on that liquid in the canister.

If you want to see what I'm talking if you want to see what I'm talking about search OTC fuel injection cleaner tool.

I don't know where you live but if you live near me we can always meet up then I can let you use mine if you need it clean? The solution that you use in those cleaners is actually usable in any of the vehicles you have. How many vehicles do you maintain? As it may be more feasible for you to just buy the tool if you have a air compressor. Then you just buy the solution and do it yourself. GM / ACDelco, BG and many others make fuel injection system cleaning fluids for these type of fuels.

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[dtnel78]

No, I have never had any other fuel induction service performed.
 
I just cleaned my Mass Airflow Sensor & I am cleaning the throttle body today too...
(cheep trys)

BE careful of what you use to clean the mass airflow sensor in regards to the TYPE of cleaner and in regards to the throttle body cleaning make sure you don't scratch the coating as the throttle body is coated and can be scratched very easily if using the wrong cleaner or TYPE of brush. Excuse the caps on some words as those pop up on their own as I use some words in some places where I have to use it for the search term.

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[Bad Bowtie2]

Thank you for the reply’s & suggestions. I can’t hardly believe nobody else has commented.

 

I only used CRC brand throttle body & electronics cleaner. Nothing harsh on the throttle body. I sprayed it down 1st, then sprayed some CRC onto a clean shop rag. I used that rag to clean up the housing & butterfly plate. I left the throttle-body on the intake & left the electrical harness plugged in too. 

 

The mass air-flow sensor didn’t look bad, but I sprayed it down anyways & let it air dry while I cleaned the throttle-body.

 

My my truck ran kind-of funny when I first started it up. Idle was off SLIGHTLY, not high RPM or crazy, but different. It seems to have improved after driving around town some.

 

All this cleaning definitely helped the throttle response & my truck does run smoother now. But my at idle still doesn’t seem 100% quit right, like it used too. We are getting close though. 

 

I wonder if if I should get a tech at work to do the throttle relearn procedure?

I do not own any kind of scan tool. I’m not a programming or electrical genius by any means either. LoL

 

I’m just a shade tree guy. I have no air compressor or air tools- I’m an old school bloody knuckles wrencher. I live in Wichita Falls, North central Texas.

 

I bought this truck new. I maintain it, my wife’s older Ford SUV, and I have an old Thunderbird I work on too. I learned car stuff from my dad (passed away now), & I’m a parts-man at a multi line dealership. So I get parts cheep. LoL

 

I wonder at 108,000 miles if my fuel pump could already be weakening? The only thing that makes me think it is not a fuel pressure issue, is that the truck runs very well at both low & high end speeds. There is no delay or hesitation. Also, don’t most fuel pumps start “go out” around 140-200k??

 

 

[dtnel78]

Plugs, wires @ 100k? Changed air filter lately?

You can post on scannerdanner.com. great people over. All very well versed in advanced diagnostics it seems plus the regular stuff.

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[dtnel78]

Also you're not in the salt belt as I am. Replaced my fuel pump at 70k miles as the bend in the line on the outside of the pump leading to the vehicle front was rusted thru.

You could check your fuel pressure.

IF you need those specs and such P.M. me thru the messaging system and we can chat off the forums.

I can put those specs and such on paper and email them to you.

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[Bad Bowtie2]

Yes, I do know about maintenance. 

 

Instead of replacing my air filter earlier this year (January), I installed one of those new Air Raid Jr intake kits.

 

It gets rid of that restrictive, noise cancelling air tube “maze” & replaces it with the smooth, straight shot to the throttle body, air tube. I went with the dry type filter & had just cleaned it out a few weekends back- during my last oil change.

 

My fuel pressure, key on, should be at 60psi, correct?

 

I’m happy to down here in Texas- away from that rust belt. Sucks to have to replace a fuel pump for that reason!!

[dtnel78]

Key on Engine off fuel pressure should be at 50-60psi. It may take a couple times of cycling the key to get it there initially. When you turn the key off the fuel pressure shouldn't drop more than 5psi over a 1min period.

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[dtnel78]

You mentioned that filter cleaning a few weekends back and in your original post you mentioned it's been going on approximately 2 weeks or so.

Sometime aftermarket filters have been know to cause issues which is one reason I got rid of the K&N filter I had in my 06 Impala. There was known issues so I tossed it.

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[sefiroxx]

I have a burb and a Sierra, fuel pumps replaced around 100-125 on each.

Attach a free rental fuel pressure gauge to verify good pressure. If low, change fuel filter and retest.

You'll want to get a scanner to monitor sensors especially the o2 sensors. You might find the engine is running rich or lean that will help focus your diagnostic effort.

[Bad Bowtie2]

39 minutes ago, sefiroxx said:

I have a burb and a Sierra, fuel pumps replaced around 100-125 on each.

Attach a free rental fuel pressure gauge to verify good pressure. If low, change fuel filter and retest.

You'll want to get a scanner to monitor sensors especially the o2 sensors. You might find the engine is running rich or lean that will help focus your diagnostic effort.
 

Gosh, that seems early on an OEM fuel pump. But I understand IT CAN HAPPEN.

 

That said, I would figure a delay or dead spot at least at highway speeds, or full throttle.

 

This generation of GM trucks has no serviceable fuel filter.

 

I installed GM O2 sensors at 95K. All four, just for maintenance reasons.

 

Edited August 20, 2019 by Bad Bowtie2

[riverbanks]

Is the new air intake tight,no leaks? and I had a fram ultraguard air filter give me trouble once,too restrictive right out of the box,and you could disconnect electric connection to MAF,test drive,let it rely on other sensors, sometimes,just cause a MAF is clean doesn't mean it's good,and hopefully it's a delphi

[Bad Bowtie2]

All connections are tight.

 

I bought this truck new. It is all Genuine GM. Mass air flow is the original 

 

Edited August 21, 2019 by Bad Bowtie2