2003 4.8 rough idle / misfire

[Languor]

Hi guys and gals.  Just recently got a 2003 Sierra 1500 4.8 4x4 z71 extended cab with 300,000km on the clock.   

 

Ive been noticing it hard on gas and idle isn’t really smooth, especially when it’s colder sometimes I can see the tac jump a little.  When it’s cold sometimes the engine light will flash for a few minutes.   

 

But when it’s cold sometimes the fuel gauge goes to empty and sets the gas light on and then comes back to normal after a minute or two.    Use to have issues with four way randomly coming on, but that stopped for now so far.  

 

So so far I have swapped two different fuel pumps (both came from tested and running parts trucks) , new ngk wires, new ac Delco plugs

 

sometimes you can hear what I think is a sparking noise from the passenger side. 

 

I dont have a lot of money and trying to fix this without a garage.  Any help be greatly appreciated.   I hooked up my phone and torque app and have attached the error codes and some data the app gave me.  

 

I just dont don’t want to be throwing parts at it trying to guess what’s wrong.   Thanks for your time! 

 

 

[sefiroxx]

Sounds like missing 1-2 cylinders or stuck iac, these would give the same symptoms , low idle to the point of engine shutting off

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[Languor]

4 minutes ago, sefiroxx said:

Sounds like missing 1-2 cylinders or stuck iac, these would give the same symptoms , low idle to the point of engine shutting off

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Hmm.  I do know too that it is a tad hesitant from a dead stop.   It’s never shut off on me though yet.  Some days it can have the tac fluctuations a bit at idle. 

 

I wonder what to try next.  I tried to include as much info from the pics as I could I’m still new to these apps.    My brother has the same motor and gets way better mileage then I do now. 

 

I was was hoping the data I included would be able to tell something? But it’s still somewhat French to me.  And I don’t want to go get coils or something if it isn’t that.  I do have a intake gasket in the box sitting here... but wasn’t sure if that was it.  

 

Thanks for for the reply btw! 

[sefiroxx]

Have you pulled codes?
-May need a reader that can give you afm ratios to see if you are running lean or not.
- Timing light to see if each coil is working
- fuel pressure gauge to see if things like filter and fpr are working
- EGR could be stuck open causing problems at idle or high acceleration
- etc, etc, etc

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[Languor]

On 2018-03-27 at 7:22 PM, sefiroxx said:

Have you pulled codes?
-May need a reader that can give you afm ratios to see if you are running lean or not.
- Timing light to see if each coil is working
- fuel pressure gauge to see if things like filter and fpr are working
- EGR could be stuck open causing problems at idle or high acceleration
- etc, etc, etc

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I have a obd Bluetooth reader with android phone, some screens can be found here with the codes:

 

 

[sefiroxx]

O2 sensor on bank one is not providing feedback on short term. Possibly faulty O2 sensor or pigtail

Misfire are likely increased when engine stumbles, so consider these as lower priority for now

Lean banks could be vacuum leaks or low fuel pressure or other:
- See above on fuel pressure.
- As for vacuum leaks, smoke test to see where smoke is being pulled in. Highly volatile cleaner could spayed around intakes to see as well. Clean the throttle and butterfly as these, if dirty, could be letting air leak by.
- failing IAC could also create problems at idle

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[Languor]

12 hours ago, sefiroxx said:

O2 sensor on bank one is not providing feedback on short term. Possibly faulty O2 sensor or pigtail

Misfire are likely increased when engine stumbles, so consider these as lower priority for now

Lean banks could be vacuum leaks or low fuel pressure or other:
- See above on fuel pressure.
- As for vacuum leaks, smoke test to see where smoke is being pulled in. Highly volatile cleaner could spayed around intakes to see as well. Clean the throttle and butterfly as these, if dirty, could be letting air leak by.
- failing IAC could also create problems at idle

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Thanks.  I will check into these.   Doesn’t the truck not use o2 sensors until it’s warmed up? So that wouldn’t explain the rough when it’s cold as well?

 

edit: I have a mahle ms16340 intake manifold gasket from rock auto here.  I may look into seeing how hard them are too change / see if I need any special tools.  And give that a go.  

[sefiroxx]

You had only started when it was cold outside - not when warming up.

Yes, system will run in open loop until certain warm conditions are met. On older vehicles, it was the water temps, on more modern, it was the 92 sensor heating up. On some vehicles, it will return to open loop under certain conditions (ie WOT)

Your pics did not indicate if the system was in open or closed.

Before throwing more parts (& labor), do the diagnostics first.

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[Languor]

14 hours ago, sefiroxx said:

You had only started when it was cold outside - not when warming up.

Yes, system will run in open loop until certain warm conditions are met. On older vehicles, it was the water temps, on more modern, it was the 92 sensor heating up. On some vehicles, it will return to open loop under certain conditions (ie WOT)

Your pics did not indicate if the system was in open or closed.

Before throwing more parts (& labor), do the diagnostics first.

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Them pics was when motor was just started.  Except the freeze frame data of course.  

 

Took engine cover over off and noticed the canister with the green valve on it in the front by throttle body, Was able to wiggle yet the bolt tightened.   Debating getting washers or something to tighten it more.  Wondering if this could be it or part of it.  

 

Edit:   I got a free day today so I’m taking the intake manifold off and going to throw these new gaskets I had sitting in my house.       I’ll keep you guys updated.  Thanks! 

[Languor]

Just got in from a full days work on the truck.  Man the intake gasket took way longer then I thought.   Old gaskets looked warped.  They were orange if that matters.  

 

Its almost back together.  But I’m done for the day.   All but one bolt tighten on the manifold.   The back one on the drivers side doesn’t seem like it wants to grab.   Hoping it doesn’t have to be pulled again.   / hoping it’s not the knock sensor wire in the way knowing my luck.  

I will keep the thread updated.   

[sefiroxx]

That 'canister' is the evap purge solenoid, for opening up the line to the charcoal canister absorbing fumes from the fuel tank. The gap would be sealed tight (with oring), the valve inside could be tight as well , if not, the system will throw an evap code (pollution control).

The valve allows for releasing pressure and for testing of the system will hold pressure.

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[Languor]

18 hours ago, sefiroxx said:

That 'canister' is the evap purge solenoid, for opening up the line to the charcoal canister absorbing fumes from the fuel tank. The gap would be sealed tight (with oring), the valve inside could be tight as well , if not, the system will throw an evap code (pollution control).

The valve allows for releasing pressure and for testing of the system will hold pressure.

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Finally got the intake gasket job done.  Had reseat the manifold for other bolt to line up. 

 

That canister where here talking about, that magnetic stick to the alternator by accident.   

 

Now it it seems it’s clicking when the trucks on.   Wonder if this is a biggie or ?  

 

Ill have ave more of a look tomorrow after work.  But seems to me the clicking is from that canister. And can only be heard at idle when outside truck.  

 

But it you were also right.  Still some idle problem.  But I think the truck runs better with the new gaskets.  

 

Thanks for for all your time and help btw !

[sefiroxx]

It has a solonoid driven piston with a spring. To force close. Sounds like the spring is broken.

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[Languor]

2 minutes ago, sefiroxx said:

It has a solonoid driven piston with a spring. To force close. Sounds like the spring is broken.

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I’ll be driving the truck like this till I get a new one.  Mean time , could it be some reason rough idle and is it going to really hurt to keep driving until I get one?  

 

I know one the codes odes was a evap code

[sefiroxx]

Same symptoms as an vacuum leak, runs lean and does idle search

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