2000 6.0L runs rough and stumbles

[fxdxharley]

Originally Posted by clinebarger

Im guessing no check engine light? Like posted before the MAF can go bad and not set a light. EGR valve stuck part way open, Vacuum leaks, TPS sensor with a dead spot. If you do have bosch plugs throw them away there junk. Ive always ran NGK V-power plugs there cheap and a good plug never had a problem.

have you checked fuel pressure? Key on engine off 55-62 PSI.

Nope no check light. I've unpluged both the maf and tps and ran it to see if there was a difference none noticed. i do have the bosh platums. How can i check to see if the egr valve is stuck? Never check feul pressure. I hope its good, the pump is only 2 yrs old.

[truckdude239]

bad fuel pressure regulator I've seen it many time on these

[fxdxharley]

Originally Posted by truckdude239

bad fuel pressure regulator I've seen it many time on these

Nope, changed that too when it had a hard starting issue.

[basemodel67]

Where is is the regulator on these things? Maybe I should change mine. BTW, when my truck broke a valvespring, the check engine light never came on when I thought for sure it should...

[Shon]

Originally Posted by basemodel67

Where is is the regulator on these things?

If you have a feed and return line on the fuel rail then the little round thing that has a vac line attached to it is the regulator, if you only have 1 line to the rails then it is in the tank, part of the fuel pump assembly.

[fxdxharley]

that is correct. it is on the drivers side fuel rail. check and see if it is good is by running the truck or cycle the fuel pump with the key, shut it off then up plug the vac line from it. If gas comes out of the port then it is no good. A nother sure way to tell is if your truck starts hard ie cranks over for a little bit before firing up. the pressure reg is a dealer only item and is just over a $100 bucks.
a broken valve sring wouldnt trip the check light.

[truckdude239]

i did not think of the valve spring but they are common on these style motors

[heavychevy77]

I've got the same issues with hesitation and stumbling on my 2000 6.0. The fuel pump took a dive so I've already replaced that. I've put in a throttle position sensor, crank sensor,mass air sensor, and still falls on its face when you try to accelerate. I took it to a shop and had it plugged into a scanner that uses live feeds. It told me that 4 out of the 8 coils were missing under a load. I just ordered a set of 8. This truck has literally broke me lol
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[heavychevy77]

I forgot to mention that I also did a fuel filter and regulator when I did the pump. Also, keep a good eye on the fuel filler neck. Apparently they're known for rotting out and the rust falls down in the tank along with the outside elements. It was a mess!
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[CAGRacing]

Don't pay someone for a live fuel pressure feed. I was a mechanic and all we do is take off the engine cover and connect our mechanical fuel pressure gauge to the shrader valve and drive the thing. save your money.
I'd check pressure first then grab a bottle of brake parts cleaner and a roll of shop rags.
Clean the throttle body, pull the egr valve and clean it out. then reach as far as possible into the intake
if you don't have cash for injectors pull them out, remove all rubber and soak them in acetone over night
You'll be amazed what it'll remove.
Oh and when I said a can of brake parts cleaner I mean a case.
A lot of problems with new gm motors are traced back to carbon build up and intake gaskets.

But I'm new here so don't take my advice as Gospel.

[bighaas79]

I'd put money that it's not coils, and if you just bought 8 of em you wasted your money. I have never seen one go bad, not that they can't, but extremely unlikely that 4 went at one time. If you did have 4 dead coils you should be looking at power supply issues before replacing coils. Personally if they told you that it needed coils from just data streams and not actually testing anything, i'd say they are just tryin to suck ya for money and don't really have any idea what they are talkin about. What are the fuel trim readings at? O2 sensors responding properly? Have cats been checked to see if they are coming apart and plugging exhaust? Maf sensor readings and map/baro reading would be helpful as well. Would also check iac as well.

[heavychevy77]

Come to find out.....I had a couple cooked plugs and a bad spark plug wire. I changed the plugs and got the one wire replaced and this truck runs better than it ever has! The wire was broken internally and it was arcing to the head. This thing is a beast!
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[fxdxharley]

Originally Posted by bighaas79

I'd put money that it's not coils, and if you just bought 8 of em you wasted your money. I have never seen one go bad, not that they can't, but extremely unlikely that 4 went at one time. If you did have 4 dead coils you should be looking at power supply issues before replacing coils. Personally if they told you that it needed coils from just data streams and not actually testing anything, i'd say they are just tryin to suck ya for money and don't really have any idea what they are talkin about. What are the fuel trim readings at? O2 sensors responding properly? Have cats been checked to see if they are coming apart and plugging exhaust? Maf sensor readings and map/baro reading would be helpful as well. Would also check iac as well.

Coils are known to go bad on these. i had to replace one do to a mis fire under load. had the dealer scan it during a test drive. all though never heard of 4 going at once. I still have minor issues with rough idle and some hesitation. Ive changed and checked everything i could. i just deal with it now. its got 180 k

[heavychevy77]

I would seriously consider looking into the fuel filler neck and the fuel pump. The filler neck was completely rusted out so the rust, water, mud and every other outside element went down inside the gas tank. It was messy and a pain to fix and clean, but what a huge difference! My gas mileage even improved
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[fxdxharley]

good suggestions to look at but not an issue on mine. i changed the pump and filter a few yrs back and just had the bed off to do some body rust repair, filler neck is fine. im thinking a nother bad coil pack. have to bring it back to dealer to be scaned.

[bighaas79]

Originally Posted by fxdxharley

Coils are known to go bad on these. i had to replace one do to a mis fire under load. had the dealer scan it during a test drive. all though never heard of 4 going at once. I still have minor issues with rough idle and some hesitation. Ive changed and checked everything i could. i just deal with it now. its got 180 k

Like I said. Not saying that it's not possible but I have literally worked on hundreds of these trucks and have yet to run into a bad coil. Can one go bad... heck ya. I'm just saying personally from what I've experienced highly unlikely. And really as far as the dealer determining it was a bad coil using a scan tool while on a test drive, unless they were current ramping it with a low amps probe and checkin primary ignition voltage waveform with a good labscope, I find hard to believe. Unless it produced primary ignition circuit codes? Even then I would be testing wiring going to the coils before replacing, because I HAVE run into wiring issues to the coils being an issue. Usually due to rubbing the harness or critters chewing the wiring up. Now if you were talking fords, it would be one of the first things I would check. I couldn't even begin to tell you how many ford coils I have replaced, and spark plugs that were blown out, or stuck in. And if you haven't changed the filter since you put the pump in a few years ago I would be checking that as well. The biggest killer of fuel pumps is the fact that the filters don't get changed often enough. Depending on how much you drive, I usually recommend yearly or 15,000 miles or so. If they are still really clear I won't change em out but if there is even the slightest restriction vs. a new one it gets changed. Why take the chance of hurtin the pump for a measly 5 bucks or so.

[clinebarger]

Originally Posted by bighaas79

Like I said. Not saying that it's not possible but I have literally worked on hundreds of these trucks and have yet to run into a bad coil. Can one go bad... heck ya. I'm just saying personally from what I've experienced highly unlikely. And really as far as the dealer determining it was a bad coil using a scan tool while on a test drive, unless they were current ramping it with a low amps probe and checkin primary ignition voltage waveform with a good labscope, I find hard to believe. Unless it produced primary ignition circuit codes? Even then I would be testing wiring going to the coils before replacing, because I HAVE run into wiring issues to the coils being an issue. Usually due to rubbing the harness or critters chewing the wiring up. Now if you were talking fords, it would be one of the first things I would check. I couldn't even begin to tell you how many ford coils I have replaced, and spark plugs that were blown out, or stuck in. And if you haven't changed the filter since you put the pump in a few years ago I would be checking that as well. The biggest killer of fuel pumps is the fact that the filters don't get changed often enough. Depending on how much you drive, I usually recommend yearly or 15,000 miles or so. If they are still really clear I won't change em out but if there is even the slightest restriction vs. a new one it gets changed. Why take the chance of hurtin the pump for a measly 5 bucks or so.

X2!!!! It is very rare for a coil on any GenIII engine to fail. I havent replaced one either.

[fxdxharley]

Originally Posted by bighaas79

Like I said. Not saying that it's not possible but I have literally worked on hundreds of these trucks and have yet to run into a bad coil. Can one go bad... heck ya. I'm just saying personally from what I've experienced highly unlikely. And really as far as the dealer determining it was a bad coil using a scan tool while on a test drive, unless they were current ramping it with a low amps probe and checkin primary ignition voltage waveform with a good labscope, I find hard to believe. Unless it produced primary ignition circuit codes? Even then I would be testing wiring going to the coils before replacing, because I HAVE run into wiring issues to the coils being an issue. Usually due to rubbing the harness or critters chewing the wiring up. Now if you were talking fords, it would be one of the first things I would check. I couldn't even begin to tell you how many ford coils I have replaced, and spark plugs that were blown out, or stuck in. And if you haven't changed the filter since you put the pump in a few years ago I would be checking that as well. The biggest killer of fuel pumps is the fact that the filters don't get changed often enough. Depending on how much you drive, I usually recommend yearly or 15,000 miles or so. If they are still really clear I won't change em out but if there is even the slightest restriction vs. a new one it gets changed. Why take the chance of hurtin the pump for a measly 5 bucks or so.

The tech at the dealer pluged in there obd scan tool and we went for a drive. code for mis fire on cyl 2 came up under load. he then swapped that coil with a different cyl and the same code came up for that cyl. put a new coil on and code was gone. So i tend to believe the tech and my own eyes seeing the codes. all the wiring is fine, plugs are new, wires are new. maybe a new filter wont hurt but i dought that is my problem.