Truck question.

[polarisdragon800]

I have a question about my truck. It's an 2003 Chevrolet 2500 with the 6.0L. It had a misfire, since I bought it used in March 2013 it has shook a bit here and their. I had it in at the dealership not long after that to get it programmed so that it ignores that the cats are cut out, anyway the mechanic mentioned that it wasn't running at its best. He said that it had a misfire on cylinder 1 and 8. I replaced mass airflow sensor, as it was throwing a code. Replaced, plugs before that and wires after, replaced coils on cylinders 1 and 8. It still has the missfire, sometimes worse than others, mainly when it cold starts, then you notice it missing. I've ran fuel conditioner through it various times. Have true dual exhaust so I can defiantly tell that both banks arean't firing in sequence. I have searched and have found that it could just need a simple Crank Relearn? Is this possible that this would cause it? When I first bought it I thought maybe it just needed to be rode hard for a bit to clean some carbon out and some new plugs. That was in March, I now know that it defiantly has a missfire. Anyone have an idea on where to start now? Thanks.

 

[powder junkie]

I have a question about my truck. It's an 2003 Chevrolet 2500 with the 6.0L. It had a misfire, since I bought it used in March 2013 it has shook a bit here and their. I had it in at the dealership not long after that to get it programmed so that it ignores that the cats are cut out, anyway the mechanic mentioned that it wasn't running at its best. He said that it had a misfire on cylinder 1 and 8. I replaced mass airflow sensor, as it was throwing a code. Replaced, plugs before that and wires after, replaced coils on cylinders 1 and 8. It still has the missfire, sometimes worse than others, mainly when it cold starts, then you notice it missing. I've ran fuel conditioner through it various times. Have true dual exhaust so I can defiantly tell that both banks arean't firing in sequence. I have searched and have found that it could just need a simple Crank Relearn? Is this possible that this would cause it? When I first bought it I thought maybe it just needed to be rode hard for a bit to clean some carbon out and some new plugs. That was in March, I now know that it defiantly has a missfire. Anyone have an idea on where to start now? Thanks.

Injectors good? Or tested?

 

[growly]

X2

sent from the van across the street.

 

[polarisdragon800]

Injectors good? Or tested?

Nope, havn't been tested.

 

[ATV Rancher]

We have an 06 Chevy with that motor that my son used to drive, that had similar problems. It finally got real bad and he said the exhaust manifold was red hot when he parked it. Turned out it had a broken valve spring. You might consider a compression check.

 

[tex78]

Also betting if it runs for say 1 my name and gets better

Intake gaskets might be leaking when cold , then warm up and seal

sent while I should be drinking tea's

 

[tmo1620]

The old mans 05 6.0L was doing the same thing, chased the problem around for a couple months with no luck, replaced and fixed a few minor things, just slowly kept getting worse, he ended up just tossing a used 6.0L with 110,000km on it that he got from a guy he knows in Saskatoon, was apparently pretty reasonable for price and in the end was probably cheaper in the long run

 

[jjack]

Injectors get bad and leak by flooding those cyilinders cheap diagnose buy new injector and try it

 

[polarisdragon800]

Truck has 200,000km on it. Bought it in the spring last year with 180,000km on it, has had misfire since day one.

Here's what I have done over the course of the 20,000km I have owned it.
-K&N air filter
-New Spark Plugs
-New spark plug wires
-New Coils on cylinders 1 and 8. (Which are the ones the dealership say were missing)
-New Fuel Filter
-New Mass Airflow sensor (Dealership Said that it was throwing a code).
-Ran plenty of tanks with Fuel Conditioner in it.
-Had Cats taken out.
-Had Dealership program to ignore O2 sensor codes because of cats being taken out.
-Cleaned Throttle Body with Seafoam.
-Installed True Duel exhaust.

Here's what I have came up with.
-Code: PO171 (Lean left bank)
-Code: PO174 (Lean right bank)


I put a screwdriver to the injectors and listened, they all seem to be pulsing at the same rate. I checked the Throttle Body and intake to make sure it was fitted properly and it was. It does it mostly all of the time, but more noticeable with cold starts as the miss effects it when it high idles. But it will do it in the summer on a warm day, seems to stutter when I stop at a stop sign or drive through. You can feel it jerking when it lugs up a hill. I am going to do a compression check.

 

[Summitric]

Could be vacuum leak, poor injectors, bad plugs/coil or wire, valve spring or lifter problem, carboned up valve -- valve seals? Etc etc etc...... Best to get it diagnosed somewhere, then you could fix yourself if need be... Cylinder balance test and good scanner test and scope test should pinpoint the problem

 

[cancritter]

awnsers>>

 

[polarisdragon800]

Just got a PO300 code. Random missfire.

 

[growly]

Would check fuel pressure. SB 55ish psi. If fuel pressure is ok, pull the intake off and check/redo the seals. You said it has a k&n. Stock airbox and plumbing? If so, check for splits in the inlet hose between the throttle body and mass airflow sensor.

sent from the van across the street.

 

[cancritter]

hate K&N...if oiled check mass air flow sensor to enshure its not covered in oil

 

[Badass69]

Intake leak of some form. Possible fuel pressure issue too as it needs around 60 at the rail. Regulator is up on the rail as well... you have the last year of the return style fuel system with an external filter in the frame... which they changed. Surprised the dealer never checked fuel pressure honestly. Knock sensors throw all kinds of stupid codes when they start to go bad.... and if it is an intake leak do them at the same time. The intake is where I would go if fuel pressure checks out. The gaskets on the 03 and older have an orange o ring and are notoriously bad for leaks. 04 up has an updated set with the green o rings and they don't leak nearly as often. Smoke machine or even careful use of propane. 1 and 8 are where I would start.... they are on the end on either bank and that is usually where the leaks start.


Sent from the Great White North

 

[polarisdragon800]

Turns out it was plugs.. When I bought it I put NGK's in it 10 months ago, it helped it a bit but eventually for worse again. I guess Chevs don't like anything other than AC Delco's. Fuel pressure was checked and all of that was good, which I am happy about.

 

[Badass69]

Odd. Never had an issue with NGK. That said I finally swapped my 05s original plugs at 214k... still had near perfect gap and would have been fine. Plugged the stock delco iridiums back in... at least good for another 214k lol.

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