Periodic rough idle, codes within thread. Plz help!

NT1078

Original poster
Member
Mar 24, 2014
76
Hi all,
I am experiencing a periodic rough idle however when given some gas it runs fine. It drives good, no loss of power however the curb idle performance varies- sometimes fine, other times quite rough. Earlier today I removed the MAF sensor to clean it and checked the air filter. I cleared the stored codes and this evening experienced rough curb idle again and threw the following codes:
Po171, Po134, Po300.

Suggestions appreciated
Adam
 

Reprise

Lifetime VIP Donor
Supporting Donor
Member
Jul 22, 2015
2,724
Check out my thread "guessing I need an O2 sensor" from a couple of days ago.

Odds are, you have an intake leak. If you have something that can read O2 sensor voltages & fuel trims, you can verify.

P0171 is 'lean bank 1' (driver side). P0300 is 'random misfire'
I know those two from memory.
And the 134 concerns the upstream O2 sensor (the one before the cat) on driver side.

If you have a 1/4" drive torque wrench, you can check to see if your manifold bolts are tight (10mm, to 89 INCH /lb). Work from inside out, alternating sides.
 
Last edited:
  • Like
Reactions: Mooseman

NT1078

Original poster
Member
Mar 24, 2014
76
Thanks so much for the advise, I will start with that and go from there. Today it seems to be behaving itself, so it is very random, but seems more so when the vehicle is properly warmed up. I have access to a 3/8" torque wrench, hopefully that will suffice. I assume you are referring to intake manifold bolts, so I will need to take apart the breather assembly to access?

Cheers,
Adam
 

Reprise

Lifetime VIP Donor
Supporting Donor
Member
Jul 22, 2015
2,724
No, a 3/8" will not suffice, unless it's calibrated in inch-lb (most are ft-lb), or you do the conversion - which is really too low a value for a ft-lb based wrench, anyway (a torque wrench has its greatest accuracy in the 'middle 80%' of its range, as it were.

The other part of your follow-up is my fault, b/c I thought you had the V8, the way I read your post. But you have the I6, so the intake is different on yours, and since I'm not familiar with the I6 intake, I don't want to tell you how to 'do this', as it may be incorrect.

I *do* think you should check on the intake, though. With the appropriate tool :smile:

PS: Make sure you validate the torque value for the I6 -- the one I gave was for the V8. If you need specs, the service manuals are on this site (a link can be found on the sig line of any of Mooseman's posts)
 
Last edited:

djthumper

Administrator
Nov 20, 2011
14,950
North Las Vegas
Don't forget to clean the throttle body while you are going through all of this.
 
  • Like
Reactions: Maverick6587

NT1078

Original poster
Member
Mar 24, 2014
76
To clarify mine is indeed the 5.3l V8 model
 

NT1078

Original poster
Member
Mar 24, 2014
76
So my latest development is I have noticed the smell when its idling poorly of unburnt fuel. It is pretty strong. We have a good Scan Tool at work I am hoping to hook on and see what it comes up with.
 

C-ya

Member
Aug 24, 2012
1,098
The smell of unburnt fuel is probably due to the misfire not burning that fuel. Since it is so random, it hasn't identified one (or more) cyllnders as the culprit. Check the misfires section and see if you can see which one(s) are causing the problem. Once you see what is happening, it might lead to the cause. Maybe a common item is affecting the cylinders and causing the misfires.

If you have Torque and an OBDII Bluetooth scanner, you can see all cylinder's misfire data, live and historic.
 
  • Like
Reactions: Mooseman

NT1078

Original poster
Member
Mar 24, 2014
76
I think I see something, a #1 misfire. Is the #1 driver's side, closest to front of motor?20190405_200908.jpg
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
For Identifying the Cylinder Positions and Firing Order on the GM 5.3L Engines with Coil Near Plugs:

GM53LFIRINGORDERCOP.jpg


For the Sake of your Sanity in avoiding Galling and Stripping the Wrench Hex Flats off of the O2 Sensor during the R&R:

O2SENSORSOCKET.png


https://www.amazon.com/s?k=o2+sensor+socket&crid=I14TNWHCXL83&sprefix=O2+SENSOR+SOCKET,aps,174&ref=nb_sb_ss_i_1_16&tag=elightbars-20

For the same reason… the NEXT time you need to perform the O2 Sensor R&R… and use this stuff parsimoniously on the Threads ...to avoid contaminating the sensitive Cubic Zirconium - Piezoelectric innards of the O2 Sensor:

51qq3U1tw4L.jpg


https://www.amazon.com/dp/B0002JN57E/?tag=gmtnation-20

...and for replacing a Failed CNP Coil Pack if necessary... (Stick with ACDelco or Delphi):

DELPHI53LCOILPACK.jpg

 
Last edited:
  • Like
Reactions: Redbeard

NT1078

Original poster
Member
Mar 24, 2014
76
Thanks for the info. Here is what I did today: Traded coil pack #1 and #3 and still saw a cylinder 1 misfire. Replaced #1 spark plug snd the #1 ignition wire and still suffering a #1 misfire. Whatever is going on is causing black smoke from the tail pipe and the smell of unburned fuel. The problem like karma chameleon comes and goes. Other times this thing runs fine, it's very odd.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Maybe a leaking injector? You should do a compression test.
 

NT1078

Original poster
Member
Mar 24, 2014
76
Thanks, are you suggesting it could be the broken valve seat I read about? Wouldn't that make it a constant misfire? This one comes and goes.
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
I like @Mooseman 's suggestion that a Clogged Electronic Fuel Injector is the MLC here (Most Likely Culprit) necessitating the R&R of the Intake manifold to perform the EFI(s) R&R. However, it might be worth widening your gaze and also consider the following things on the rungs further down on your solution ladder:

You mentioned cleaning the MAF Sensor and THEN detecting the three Codes afterwards. The MAF Sensor - Inlet Air Temperature actually WEIGHS the Air Stream as it passes through it so the PCM can add that detail into its F/A Calculations and Tables for a whole range of RPM and attempt achieve Stoichiometric precision of around 14.7 parts of Air to 1 part Fuel at Sea Level Air Pressure being 14.7 PSI. If the Upstream 02 Sensor eventually senses that Bank 1 is Too Lean... then it will prompt the PCM to dump more fuel to compensate for the imbalance in the F/A ratio.

All that said... the MAF Sensor is NOT very tolerant of being cleaned using anything other than CRC MAF Sensor Cleaner ...rather than just using Brake Cleaner or ANY other Cleaning Solvent. So if you tried anything else... there is the possibility of the MAF suffering internal damage to its delicate sensing mechanism.

The other possibility involved is that if you have an errant Hydraulic (Non-AFM Non-DOD Style) Camshaft Roller Lifter in Bank 1- Cylinder 1 that has gotten clogged with any small dirt and sludge particles and it is not "Plumping Up" with sufficient Internal Oil Pressure to actuate the Push-Rod(s) to Rocker Arms to Valve Stems properly ... it can result in Low Cylinder Compression with a consequential P0301 Mis-Fire Code occurring.

If this is happening now... then it (or ALL of the Bank 1 Lifters... if you like) might need some strong inducement to improve by being doused internally with some Berryman's Chem Tool Carburetor Cleaner Spray and get flushed clear and clean by using the easy and straightforward techniques and suggestions mentioned by Brian of Briansmobile1 in this Youtube Video:

 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Thanks, are you suggesting it could be the broken valve seat I read about? Wouldn't that make it a constant misfire? This one comes and goes.

Anything is possible. Have to check everything systematically and the mechanical health of the engine must be taken into account so a complete compression test is needed.

For the fuel injector, if you don't have access to a scanner that can do an injector balance test, you could swap the injector from the #1 cylinder with #3 and see if the misfire follows it.
 

NT1078

Original poster
Member
Mar 24, 2014
76
These are great suggestions, thank you all. I have in my posession right now a good Snap On scanner that I borrowed from work over the weekend, trouble is I don't know how to decipher the data. I will post some photos and videos of some scans, perhaps you fine folk could decipher it?
 

NT1078

Original poster
Member
Mar 24, 2014
76
Ok, here are some links to videos of data I have collected from the scanner. I am hoping someone can decipher it.

 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Your misfires are all over the place and in both banks. Odd that it seems to be worse on the front 4 cylinders than the rear.

I'd still do a compression test on all the cylinders. Then check the spark on each cylinder using spark testers to be sure they all fire regularly. It would be strange for multiple coils to be failing at the same time however could be a wiring issue that's common to all of them, like a ground that's intermittent.
 

NT1078

Original poster
Member
Mar 24, 2014
76
So, here is an update of sorts. Have now changed all plugs and wires, gave it a Seafoam treatment and it was at tge garage today. It was still misfiring and carrying on. He changed the MAF at a cost of $270. Took it for a drive, all was good. Then it started again, so he put in my old MAF so I wasn't on the hook for it. He has suggested changing the bank 1 sensor 1 o2 sensor. A relatively inexpensive part so it's worth a shot. This evening I sprayed the throttlebody liberally with carb cleaner. It now runs worse, yay me.
 

Reprise

Lifetime VIP Donor
Supporting Donor
Member
Jul 22, 2015
2,724
If you moved the butterfly on the TB while cleaning, you may have thrown off the throttle position sensor (TPS). Especially if you left the battery connected. I'd try disconnecting the battery for a few minutes so that the PCM does an idle relearn (do a thorough drive cycle afterward so that it learns properly).

How did those plugs look when you took them out? Was one or more of them (esp. #1) fouled? Or were they all nice & tan like cafe au lait ?

At least you didn't get reamed for the MAF!
 

NT1078

Original poster
Member
Mar 24, 2014
76
If you moved the butterfly on the TB while cleaning, you may have thrown off the throttle position sensor (TPS). Especially if you left the battery connected. I'd try disconnecting the battery for a few minutes so that the PCM does an idle relearn (do a thorough drive cycle afterward so that it learns properly).

How did those plugs look when you took them out? Was one or more of them (esp. #1) fouled? Or were they all nice & tan like cafe au lait ?

At least you didn't get reamed for the MAF!

No kidding. It was nice that I didn't get charged for that part, holy. The base of the plugs were all very black and sooty, they certainly needed to be changed regardless. Interesting you suggested the battery, as I just came in from doing that. I disconnected it for at least 20mins and drove it around the block a few times, it still runs like crap, off and on. Very strange the problem(s) come and go.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
I recently saw a video from our alumni member @MAY03LT where he strongly suggests to not clean the throttle body on V8's otherwise you need a throttle relearn. You need a high end scan tool or Tech 2 to.do this. And to.clean it properly, it has to be removed, not just sprayed in place.
 

NT1078

Original poster
Member
Mar 24, 2014
76
Yesterday afternoon I got as far as putting it on ramps and sliding my big butt under for a look. I am thinking of changing the bank 1 sensor 1 o2 as I threw P1133 a few times. I got as far as getting a wrench on which slipped off, then I noticed the wire disappears beyond the bell housing. I have reached a point in my life where I know when to hold 'em and know when to fold 'em. So I scooted it off the ramp and will bring it to the garage. I have a new sensor ready to go, let's see if it helps. The garage did confirm earlirr my waterpump is leaking, so that's something to look forward to.
 

NT1078

Original poster
Member
Mar 24, 2014
76
So here is an update: Bank 1 sensor 1 has been replaced and I am no longer getting the P1133. What I am getting now us PO300 and a PO174. It still occasionally acts up, but it comes and goes, strange. I gave it a Seafoam can in the tank and have been running higher octane gas. I also changed the air filter for good measure. If anyone has suggestions for the PO174, please let me know.

Cheers
Adam
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
These Threads address Multiple Codes (P0171 and P0174) that "lean" towards you having Undetected Vacuum Leaks in and around the Intake manifold OR the Throttle Body and Hosing that may come and go as the Engine Warms up and any such 'leak' points manage to seal themselves up temporarily, Such 'leaks' will allow un-metered or un-measured air to play havoc with the O2 Sensors detecting Too Much Oxygen in the Exhaust Stream. The O2s will alert the PCM to the 'Lean' condition and that will prompt the PCM to Dump in More Fuel to balance out the errant F/A Ratios. and elevating your Idle RPM as a result.


"Scanner Danner" will address the Diagnostic issues on a similar GM 5.3L Engine:

 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
After symptomatic confirmation, if you are considering performing this Intake Manifold Gasket Repair and/or including the R&R of any Fuel Injectors yourself... Brian from Briansmobile1 Youtube Channel shows how this procedure gets done in his nearly one hour long video:


...and another from 1Road... WITH The Knock Sensor R&R, too:


...and while you are at it... Take advantage of the opportunity to R&R The Oil Pressure Sensor with an ACDelco OEM Unit AND the Small Engine Block Oil Gallery Filter (if present) while the access to that Sensor is so easy and readily available. If you have to do this later on... this Video will show you why it will be something to consider doing with the IM Off ...before it turns into THIS kind of a serious PITA Job:

Would you rather be able to R&R this OPS while having THIS much EZ access...?

GM53LOILPRESSURESENSOR.jpg

...or have to Wrangle the Damned Thing In and Out under THESE Conditions?

 
Last edited:

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
It helps to speed it up to 1.5x. I do that to a lot of videos.
 
  • Like
Reactions: mrrsm

NT1078

Original poster
Member
Mar 24, 2014
76
These are great videos, thanks very much. I am leaning towards intake gaskets as my problems do seem more prevalent when the engine is cold. My drive to work is very short so it doesn't get much chance during the week to heat up properly, unless there is a long lineup at the Drive Thru, lol. And I indeed need to replace my oil pressure switch as it flip flops like a politician. I will do some spraying around the gasket and see what happens.

Adam
 
  • Like
Reactions: Mooseman and mrrsm

NT1078

Original poster
Member
Mar 24, 2014
76
Might have it solved! Replaced the other o2 sensor and put in a new fuel filter, and had the oil pressure switch replaced (unrelated but nice to have the gauge working) Over the past few days it has been running well, fingers crossed!
 

Forum Statistics

Threads
23,273
Posts
637,488
Members
18,472
Latest member
MissCrutcher