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Truck breaking up in higher RPMs by LitebulbwithaFiero
Started on: 12-03-2016 01:40 PM
Replies: 24 (379 views)
Last post by: LitebulbwithaFiero on 01-07-2017 01:09 PM
LitebulbwithaFiero
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Report this Post12-03-2016 01:40 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have a 2004 Sierra 1500 4x4. 2 years ago, and 30,000 miles ago I swapped in an lq4- 6.0l from 3/4 ton truck. The motor was bought from ATK performance engines.The truck is having issues with breaking up/ missing. It is more noticable in higher RPMs and gets worse as engine heats up. Wondering if any one has some advice on how to begin diagnosing the problem

Thanks,
Josh
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LitebulbwithaFiero
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Report this Post12-03-2016 04:50 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
Vacuum guage shows good. But I'm going to pull the plugs, see how they look. Then the valve covers and have a look under them. Lastly pull the rockers and do leakdown on all cylinders.

See if see any anomaly.

Have head gaskets on the way and a new set of heads sitting on the bench going on it Monday if I don't get it running good this weekend.

[This message has been edited by LitebulbwithaFiero (edited 12-03-2016).]

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LitebulbwithaFiero
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Report this Post12-04-2016 09:22 AM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
Got the garage cleaned out a bit, the Fiero moved over, and the truck inside last night. Start tearing into it a bit today.

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LitebulbwithaFiero
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Report this Post12-04-2016 07:02 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post

LitebulbwithaFiero

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Sparkplugs are a nice light tan.
Leak down is around 10% on all 8 cylinders.
Everything looks copacetic.

I did put new plugs and wires on it. The miss was still there.

Any input anyone?

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Report this Post12-05-2016 09:25 AM Click Here to See the Profile for RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
Was the old engine a 6.0 or a 5.3? Has it done it ever since the swap? (Edit - After rereading the O/P, I'm guessing this is a "new" thing.)
Is it getting enough gas?
If it was a 5.3 and you didn't change the tune (or used the same injectors) I'm thinking it may be "starving". Is it setting a "misfire" code?
Perhaps a fuel pump or regulator?

Edit - Possibly a crank position sensor? Was a "CASE learn" performed when the engine was swapped?

[This message has been edited by Raydar (edited 12-05-2016).]

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LitebulbwithaFiero
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Report this Post12-05-2016 03:25 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
The truck had a 5.3 before the 6.0l. I got a tune from Black Bear Performance to run the bigger motor. Truck has ran good for the 30k miles I have on it. So I am sure it is not in the tune. Fuel pressure checks okay and there is no check engine code for misfire, just for rear o2 sensors.
I am unsure what a case learn is.

Thanks,
Josh

[This message has been edited by LitebulbwithaFiero (edited 12-05-2016).]

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Report this Post12-05-2016 05:07 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
02 sensor reading lean?
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LitebulbwithaFiero
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Report this Post12-05-2016 05:52 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 2.5:

02 sensor reading lean?



If that is in reply to my check engine light being on for rear o2 sensors- it is on for cats not working (blew them out the tailpipe)

As for the front o2s, my laptop is down so I am unable to read the sensor outputs.
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Report this Post12-06-2016 01:03 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by LitebulbwithaFiero:

If that is in reply to my check engine light being on for rear o2 sensors- it is on for cats not working (blew them out the tailpipe)

As for the front o2s, my laptop is down so I am unable to read the sensor outputs.


Thinking maybe the cats being blown out could cause the issue? Or the front 02 sensor's known-ness cause it?
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Report this Post12-06-2016 01:05 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post

2.5

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I had a bad sparkplug wire cause that in an older engine. It would arc to a manifold. But your setup isn't quite like that.
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LitebulbwithaFiero
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Report this Post12-06-2016 05:22 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
Blew the cats out almost exactly a year ago.
It feels like, when it currently misses, like when I broke the cats and they would plug off the exhasut. The main difference between then and now, is the sound. Busted cats are loud like a rod knock. I am sure what you mean bt o2 known-ness. I did have an msd plug wire arcing to the manifold. I was happy when I saw that thinking I had it licked. But new plugs and wires seem to of made no difference.

Thanks for replies, you are helping to make me think more on it

[This message has been edited by LitebulbwithaFiero (edited 12-06-2016).]

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Raydar
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Report this Post12-06-2016 05:56 PM Click Here to See the Profile for RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by LitebulbwithaFiero:

The truck had a 5.3 before the 6.0l. I got a tune from Black Bear Performance to run the bigger motor. Truck has ran good for the 30k miles I have on it. So I am sure it is not in the tune. Fuel pressure checks okay and there is no check engine code for misfire, just for rear o2 sensors.
I am unsure what a case learn is.

Thanks,
Josh



CASE Learn is usually performed whenever a crank sensor is replaced. It also is frequently done when an ECM (or engine) is replaced. It's kind of like a "fine tune" thing. The 3800 guys do it a lot. It helps to optimize the timing of the Crank Position Sensor, engine, and PCM.
I poked around a bit, and some people say that it needs to be done in order for the misfire codes to even work, but I don't know how true that is.
In any event, if yours has worked fine for 30K miles, I'm pretty sure it's not the problem. Or at least not contributing to the poor running.

Is it possible that it's something as simple as bad gas?
How is it at low RPM, high throttle? (i.e., lugging - if it's even possible to do that.)
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LitebulbwithaFiero
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Report this Post12-06-2016 06:10 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
Gotchya. Case relearn= crank relearn

If a relearn is necessary, there is a dtc for that. I never got the dtc for needing it. But I have had misfire codes pop up.
I was low on gas so I filled it up yesterday. Drove around for a half hour. It starts out only at higher rpms, but once heat soaked it becomes more problematic. Lower rpm with load and it starts missing.

[This message has been edited by LitebulbwithaFiero (edited 12-06-2016).]

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Report this Post12-07-2016 10:15 AM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by LitebulbwithaFiero:
o2 known-ness.


I mean are the fronts throwing a code?
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Report this Post12-07-2016 10:17 AM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post

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So you have new wires, new plugs, I would suspect the next steps in the igniton system, coils?
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Report this Post12-07-2016 04:43 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
No other codes then the rear o2.

My understanding with coils is they either work or they don't. I look up testing for them, and all people say is to see if it sparks. Mine are definetly sparking
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Report this Post12-08-2016 06:38 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
Anyone have experience with EFI Live? I have a V2. I thought I couldn't use it as my laptop is broke, but from early searching, it seems to be capable of stand alone data logging. Biggest problem while searching on how to use it, most info out there is for diesels
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Report this Post12-10-2016 09:12 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
Bought a new laptop and got efilive all installed on it and working, I think. I will find out tomorrow. My tuner set me a pid list to use while doing a datalog to see if the miss can be isolated to a certain cylinder or condition.
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Report this Post12-13-2016 06:44 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
Computer shows all cylinders randomly misfiring. No obvious correlation.

So, I cleaned the throttle body and the MAF. Replaced the air filter and a cracked hose for the crank vent. Even poured a bottle of seafoam in the gas tank.
Cleaning the throttle body lowered the throttle position at idle from 14% to 6%.

But no difference in the missing and still no cel for it.

I am moving on to the power side of things. Going to put a new battery to block ground cable on and check all the harness grounds I can find.

[This message has been edited by LitebulbwithaFiero (edited 12-13-2016).]

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Report this Post12-14-2016 08:16 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
I think it is fixed. Computer connector had some corroded pins. Cleaned them and couldn't replicate the symptoms on a test drive. Will lnow tomorrow for sure with the commute home from work
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Report this Post12-15-2016 10:47 AM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
If it thinks they are all misfiring you may have found the problem, the electrical connections.
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Report this Post12-15-2016 04:54 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
All seems good. The power being back feels good.
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Report this Post12-16-2016 12:02 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
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Report this Post12-16-2016 09:48 PM Click Here to See the Profile for RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
Excellent! Good show!
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Report this Post01-07-2017 01:09 PM Click Here to See the Profile for LitebulbwithaFieroSend a Private Message to LitebulbwithaFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well, the truck has been acting up again the last couple weeks. I pulled the ecm connector and cleaned it spotless on both ends, made no difference. Ended swappimg in a clean ecm, again no difference. After the truck getting bad enough to not even start, it magically went away. Drove fine for a week, then yeaterday started acting up. Time to start grasping for straws again.

[This message has been edited by LitebulbwithaFiero (edited 01-07-2017).]

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