Intermittent CEL when weather warms-up

[TB_n00b]

Hey all.

I've been getting a CEL that from what I can tell, typically occurs on the first day of weather where temperatures break into the 40's or higher. I haven't been able to get the code read yet because the CEL tends to disappear in 2 or 3 start cycles or when the temperatures drop back into the 30s or below. Being in the northeast it's been plenty cold with only a few warmer days this winter. I've been making sure I wait for the ridiculous secondary air injector to run its cycle on each start and have been ensuring the gas cap is on tight after each fill. Beyond that I am grasping at straws. Would a Cat issue show itself with warmer weather? Or O2 sensor issues? The only correlation I can account for is the weather. I suppose it could be a gas cap issue as I do refill towards the end of every week but I always make sure it's tight.

Other info: Truck is not lacking for power, there are no misfires and I am not seeing any issues with gas mileage on my daily 45 mile RT commute. I did clean and re-oil my air filter towards the end of last year. Also had the fuel gauge sensor replaced through the non-recall. First time this issue happened was last Christmas with a temp drop from 60, 50, 40 the days prior to low 20s on the 25th and back into the 40s immediately following. The CEL hung around, so I disconnected the battery and reset the CEL. All other instances it has self-cleared after a few cold starts. The latest incident, it appeared this past Saturday (started car in low 40s, drove later in low 50s) and carried through Sunday (ran car twice when it was in the 50s), stayed on through yesterday morning (low 40s drive to work), was on during lunch drive to run errands (mid 30s) and was off on my drive home (still mid 30s). Remains off today with temps in the 20s.

4.2L '07 with 86k.

Anyone have any ideas? Hoping I can get a few days of warmer weather to see if it sticks around.

TIA.

 

[The_Roadie]

Recommend you get your own code reader so you can catch it in the act. Or read the stored historical codes. And throw in new plugs.

 

[TB_n00b]

Recommend you get your own code reader so you can catch it in the act. Or read the stored historical codes. And throw in new plugs.

I was considering checking the plugs again. They were changed out in April 2010 with 28k miles when I encountered suspected misfires and confirmed it with a code read. Issue was water running off the cowl and finding it's way into the spark plug chamber (was half full of water when I was checking things out).

This was the worst of the plugs at 28k.

 

[Robbabob]

On the same line as The Roadie, just don't buy the corded one for $100+ unless you don't have an Android smart phone.

You can get a dongle that plugs into your OBDII port and connects via wi-fi to an Android smart phone with the Torque app. Dongle as low as $13, but I had to buy the $24 one to work on both my Dodge and wife's TB, and the Torque app runs about $5 I think. Works well enough you can be inside your house diagnosing codes, rather than outside in a cold and frigged environment. The iPhone hardware and software version costs upwards of $50, I think.

Water freezing in your plug area under 30°, then dripping into the cylinder above 40° causing the CEL? Odd...

Good luck!

 

[IllogicTC]

Another big bonus with Torque is you can be in the engine bay area and monitoring, too. Again, you're not limited to your cord's reach.

I'd think the ice would thaw with any appreciable runtime, even if the temperature is under freezing, because of the proximity to the engine (as in, right on top of it).

Maybe there's ice somewhere else? Emission system somewhere, or maybe in the vacuum line running up to the resonator? Knowing which code specifically would help immensely.

 

[TB_n00b]

Thanks for the suggestions. I'll probably order a BT OBD2 reader while we're in the latest polar vortex so I can have it when we thaw out in a few weeks.

 

[TB_n00b]

Itttt''ssssssssss baccccccckkkkkkkkkkkkkk.....came on about 5 seconds after turning the engine over this morning. Was fine all weekend and all Monday. I'm really curious if it's the gas cap. Haven't paid attention to fuel level, but am starting to wonder if there's any correlation. Just under half tank this morning.

To AutoZone I go! (at lunch time...assuming it's still there...it should still be there.)

 

[dmanns67]

Anytime you get a CEL I would have the code read whether at Autozone or using the ODBII ELM327 with the TorquePro app ($20 from Amazon.com).

If you at least have a code we will be able to provide more information and experiences rather than guessing/assuming.

Sorry if I missed it, but does your TB have a DIC? If I do not tighten my gas cap, it will show up on my DIC saying tighten gas cap. I replaced my gas cap and my CEL finally came on after getting the tighten gas cap message two days in a row.

I think the CEL was p0440, Evaporative (EVAP) emission control system malfunction.

 

[TB_n00b]

I'll be getting the code(s) read today so I'll post again when I get back to the office so we can figure this out. Also buying my own OBDII reader.

 

[TB_n00b]

Ok so for the CEL we have:

P1400
P0506

So looks like it's time to clean my throttle body again!

And likely related to my faulty steering position sensor and/or a bad ground:
C0196
C0244
U1026

 

[IllogicTC]

So looks like it's time to clean my throttle body again!

Good choice. http://gmtnation.com/f25/p1400-code-1743/#post34376

 

[TB_n00b]

Good choice. http://gmtnation.com/f25/p1400-code-1743/#post34376

Heh, I actually googled the code combo before posting and guess which thread came up near the top of the list?

Oh and...now the CEL is gone. Guess the car had a good start for my commute home and this morning.

Hopefully will be able to tackle this this weekend between other commitments before my trip to VA next wednesday. Will be doing the the plugs and cleaning the MAF as well. I suspect the K&N re-oil I did late last year could be partly to blame for this.

 

[TB_n00b]

Ahhhh...glorious, glorious clean throttle body and new spark plugs. Goddamnit, I forgot how annoying removing #5 and #6 are.

 

[IllogicTC]

I suspect the K&N re-oil I did late last year could be partly to blame for this.

Someone around here mentioned how when you re-oil you're supposed to pay close attention to the instructions, and let it dry before reinstalling or something like that. I wanna say Hardtrailz or Playsinsnow mentioned that somewhere.

Ahhhh...glorious, glorious clean throttle body and new spark plugs. Goddamnit, I forgot how annoying removing #5 and #6 are.

3/8 ratchet, spark plug socket, 2 3" extensions, u-joint, and 10" extension. It wasn't all too bad for me

 

[TB_n00b]

Ha, well I don't own a u-joint, so that's part of the problem.

I just drop the plug socket with an internal rubber fitting down onto the plug, then insert the 6" ext. and then attached the wrench to break the plug loose. Then pull the 6" (socket is stuck on the plug), attach a 3 inch and remove by hand the rest of the way. Works well enough. Just forgot how I did it last time 4 years ago.

The K&N, I washed it on Friday afternoon, let it dry through Saturday evening, lightly re-oiled and reinstalled on Sunday evening. I withdraw my K&N re-oil as a possible culprit. Checked the MAF and it was pristine. Throttle body was really nasty though. Might need to do a TB clean more often than 50k.

 

[IllogicTC]

Might need to do a TB clean more often than 50k.

Yes. If you go by the OLM for oil changes, about every other oil change it'd be worth at least giving the throttle body a good eye. Or if you just want to make sure since you're already about to the point of having it off, just do a clean. I'd say every 20-25k max requires a cleaning, this is just the method I'm going with. I had cleaned mine for the first time at 105k miles, and let me tell you it was something. No real problems with idle and running, but it was still nasty.

While K&N could have something to do with it if you do the oiling wrong, it's usually just the stupid PCV valve blowing crap back up into the intake manifold.