Intermittent rough idle

[Mp619]

2013 GMC Yukon SLT 5.3L 107,000 miles

at about 90,000 mi or so i changed the plugs and wires (all ACDelco) because it was about time and i had a misfire code show up after i noticed the engine having a slight rough idle for about 5 seconds every 45 secs to 1 minute. its not crazy rough but it is noticable.

i am noticing the rough idle more now and im wondering what it could be and not hoping i will need to replace the engine since these engines are known for the lifters going bad.

i have no issues accelerating at any other speed. the rough idle lasts for a few seconds whether i am in park or in drive.

i have done no mods to the engine except for adding a K&N Blackhawk intake. I did start using Mobil One full synthetic shortly after the tune up. maybe there is some other parts i can replace that you guys can recommend i go with. hopefully @swathdiver can chime in with his wisdom.

Thanks

 

[swathdiver]

Evening Mike,

Could be any number of things. What code(s) are you getting? I would double check all the vacuum and pcv lines and the Blackhawk intake, make sure there are no leaks and nothing is loose. If a particular cylinder is acting up, it might be a good idea to swap plugs and wires with another and see if the problem moves or stays. Same with the injectors.

If you can get your hands on a Tech2, you can do all that testing sitting in the driver's seat and not bother turning a wrench! Others will chime in.

 

[Mp619]

Evening Mike,

Could be any number of things. What code(s) are you getting? I would double check all the vacuum and pcv lines and the Blackhawk intake, make sure there are no leaks and nothing is loose. If a particular cylinder is acting up, it might be a good idea to swap plugs and wires with another and see if the problem moves or stays. Same with the injectors.

If you can get your hands on a Tech2, you can do all that testing sitting in the driver's seat and not bother turning a wrench! Others will chime in.

I haven’t checked for any codes because my Check Engine light is not on. I’ll try to get a scanner on it tomorrow and see if anything comes up. Thanks



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[Mp619]

got a scanner on it yesterday and it showed no codes like i expected. I'll try to take a look at the engine to see if i notice any vacuum leaks this weekend. a co-worker also noticed the slight rough idle/sputter. i could just be over doing it but i like my engine to run as smooth as possible.

 

[the_tool_man]

got a scanner on it yesterday and it showed no codes like i expected. I'll try to take a look at the engine to see if i notice any vacuum leaks this weekend. a co-worker also noticed the slight rough idle/sputter. i could just be over doing it but i like my engine to run as smooth as possible.

There are lots of potential causes that won't set a code, at least not at first.

• Dirty injectors can cause a rough idle. Try running Lucas fuel system cleaner or Berryman B-12 Chemtool for a few fill-ups and see if the problem gets better.
• I've been told the front O2 sensors get lazy with 100k miles on them. In steady-state driving, they work fine. But they don't respond well to throttle transients or idle conditions. The only way I know to check this is to replace them.
• I don't know for sure. But I assume GM uses some sort of IAC valve for idling. That can get dirty or stick and cause idle issues. I had that issue on a Mustang once.
• A vacuum leak can cause issues. Modern ECUs can adjust fuel trim to keep the AFR in spec. But depending on the size and location of the leak, it can make the engine run rough. And the fuel mileage will get noticeably worse. Over time, it will typically set a "Long Term Fuel Trim" code.
• If your coil packs are original, it could be one of those getting weak. Eventually it will misfire badly enough to set a code, so you can identify which one it is. It might be a good idea to buy one as a spare in case it happens on the road somewhere. You don't want to run in V7 mode for any length of time.

I've see where people recommend a Tech2 scanner. I presume it can look at other non-OBDII codes specific to GM vehicles. But they're expensive.

Let us know how it goes. My 100k mile Yukon has a very occasional sputter at idle. So I'm looking at all of the above, too.

 

[Mp619]

There are lots of potential causes that won't set a code, at least not at first.

• Dirty injectors can cause a rough idle. Try running Lucas fuel system cleaner or Berryman B-12 Chemtool for a few fill-ups and see if the problem gets better.
• I've been told the front O2 sensors get lazy with 100k miles on them. In steady-state driving, they work fine. But they don't respond well to throttle transients or idle conditions. The only way I know to check this is to replace them.
• I don't know for sure. But I assume GM uses some sort of IAC valve for idling. That can get dirty or stick and cause idle issues. I had that issue on a Mustang once.
• A vacuum leak can cause issues. Modern ECUs can adjust fuel trim to keep the AFR in spec. But depending on the size and location of the leak, it can make the engine run rough. And the fuel mileage will get noticeably worse. Over time, it will typically set a "Long Term Fuel Trim" code.
• If your coil packs are original, it could be one of those getting weak. Eventually it will misfire badly enough to set a code, so you can identify which one it is. It might be a good idea to buy one as a spare in case it happens on the road somewhere. You don't want to run in V7 mode for any length of time.

I've see where people recommend a Tech2 scanner. I presume it can look at other non-OBDII codes specific to GM vehicles. But they're expensive.

Let us know how it goes. My 100k mile Yukon has a very occasional sputter at idle. So I'm looking at all of the above, too.

Thanks sir,
Here’s a list of things i did recently to help root out a few possibilities.

Switched from synthetic blend to mobil one in the summertime

Changed all spark plugs and wires with acdelco products a couple months ago

Last week, Cleaned the throttle body and MAF sensor and made sure all the connections to the Blackhawk CAI were solid without leaks.

Check for any codes and came back code free.


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[Mp619]

Thanks sir,
Here’s a list of things i did recently to help root out a few possibilities.

Switched from synthetic blend to mobil one in the summertime

Changed all spark plugs and wires with acdelco products a couple months ago

Last week, Cleaned the throttle body and MAF sensor and made sure all the connections to the Blackhawk CAI were solid without leaks.

Check for any codes and came back code free.


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A couples months ago i had a missfire code that came up so thats when i did the plugs and wires then shortly after i had a code for the passenger pre-cat O2 sensor so i replaced both pre-cat sensors.


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[the_tool_man]

Good call on cleaning the MAF sensor. I meant to mention that, as well. I'm cleaning mine tomorrow before I get it tuned on Sunday.

 

[Dmascari1984]

Any luck fixing your idle??? 2014 PPV 57xxx. I have the exact same issue tried checking everything for leaks and cleaning the MAF and TB no codes and idle sucks bad. Ran injector cleaner etc. still bad. All I have right now is blue driver scan tool. A Buddy told me to get the new GM MDI scan tool from alibaba for like $100. Supposedly that’s the same as they use at the dealer ( new version of tech2) May do that and try to hone in on the prob instead of just throwing money at stuff like I allways do.

 

[Mp619]

Any luck fixing your idle??? 2014 PPV 57xxx. I have the exact same issue tried checking everything for leaks and cleaning the MAF and TB no codes and idle sucks bad. Ran injector cleaner etc. still bad. All I have right now is blue driver scan tool. A Buddy told me to get the new GM MDI scan tool from alibaba for like $100. Supposedly that’s the same as they use at the dealer ( new version of tech2) May do that and try to hone in on the prob instead of just throwing money at stuff like I allways do.

Havent had a chance to work on the truck because of the holidays combined with work but mine is still running fine with a rough idle from time to time. Any luck with yours?



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