2000 6.0L runs rough and stumbles

[fxdxharley]

I have a 2000 silverado 6.0 with about 150k. just had the topend off to replace broken manifold bolts no where on cylinders!
It has been running rough for awhile now. under moderate load it stumbles and has a hesitation. I changed the plugs, fuel pump and filter about a yr ago. as well as the fuel pressure regulator and 2 o2 sen. No codes come up on the scanner so im at my wits end. anyone have simaliar probs? I dont want to have to pay a dealer threw the nose to figure it out.

[bwood]

I know you replaced the fuel pump and regulator, but how is your fuel pressure. You might need to find someone (a shop maybe, doesn't have to be the dealer) who has the ability to do some live sensor data logging/scanning to check the operation while running. This may help pinpoint the source of the poor operation. When did you problems start, before or after all of the parts? Did you use AC plugs?

[fxdxharley]

the problems were before all the parts. some problems went away with the new parts. like hard starting was due to the bad pressure regulator. pump was on its way out and sending unit didnt work so that was a no brainer. I have a local shop that can do a pressure check on the injectors to see if they are working. havent gottin to that yet. they also said try changing plug wires. those are original. the plugs are ac delco. it looks like it runs lean. all plugs are a very light tan almost like they were just put in with little miles and they have about 20k on them. But the shop said that these do usually run lean.

[mcbassin]

Harley,
You said the shop recommended wires? Did you change them yet? I have a buddy that changed a lot of the same parts you have turned out to be one of the wires was not putting enough juice to the plug.

[fxdxharley]

no I havent gotten a chance to go buy a set yet. plan to this w/e after payday. thanks for the info.

Originally Posted by mcbassin

Harley,
You said the shop recommended wires? Did you change them yet? I have a buddy that changed a lot of the same parts you have turned out to be one of the wires was not putting enough juice to the plug.

[truckdude239]

it really sounds like a vacuum leak to me

[basemodel67]

Fxdxharley- any updates? I have a 2000 Sierra with a 6.0 and the same problems. I am interested to see if new plug wires help. My motor seems to have a shudder to it and it idles under 500 according to the tach.

[fxdxharley]

Originally Posted by basemodel67

Fxdxharley- any updates? I have a 2000 Sierra with a 6.0 and the same problems. I am interested to see if new plug wires help. My motor seems to have a shudder to it and it idles under 500 according to the tach.

no updates yet sorry. i havent gotten a chance to work on it. it does sound like your trucks is acting just like mine. mine idles around 500 too.

[Cdshinne]

I have a 2000 5.3 with 140k on her! When i put it in gear it stumbles and when i hit the gas it hesitates. It doesn't do it as often on cooler days and runs great above 1,000 rpm I was originally thinking coils but i haven't replaced my plug wires yet!

[clinebarger]

have you tryed cleaning the throttle body bore of all the carbon?

[bigbadjohn84]

my buddy had a lot of the same issues with his HD. we ended up changing the plugs and wires, and the knock sensors. all better. turns out the plug wires were breaking down and not putting out enough juice. the engine has two knock sensors under the intake plenium. one of which was broke of (looked rusted in two) and while we were in there we changed the other as well for added insurance. not saying thats ur prob. but if you could analize live sensor data, you could see it maybe as stated before

[fxdxharley]

Originally Posted by clinebarger

have you tryed cleaning the throttle body bore of all the carbon?

yes i did clean it. it was pretty dirty thats for sure.

[Cdshinne]

Never heard of knock sensors what do they do?

[bigbadjohn84]

they pick up vibrations and detonation in the block and send that info to the computer to let it know whether to advance or retard the timing to adjust for best overall performance and such depending on set incrimites. thats a pretty basic description. otherwise... they are importand lol

[Shon]

It would be beneficial to find someone local that can log the truck while driving. I can probably help find a shop that has the equipment to do so that would be willing to help.

But the Knock sensors and the ignition is a good starting point.

Also, do you have a K&N style filter? lots of times those are over oiled and the residue gets on the MAF sensor and that messes up things big time.

[msgross]

Did you change the strainer on the new fuel pump?

[LEEVON]

coil packs will go out from time to time, a resistance check i believe will test them...

[bighaas79]

Originally Posted by LEEVON

coil packs will go out from time to time, a resistance check i believe will test them...

Not saying its not possible but I've worked on alot of these trucks and have yet to have a coil go bad. Wires and plugs are most comon issue. Fuel pressure regulators are very common as well. Hell i've done 4 of em this week alone.

[fxdxharley]

Originally Posted by msgross

Did you change the strainer on the new fuel pump?

yes all filters were changed when i put the new pump in. it came with a new strainer all ready attached.
I do need to get over to my local/friends shop and have them run it with the live scanner. money is tight so i just have to deal right now. the truck is like a woman always taken money.

[truckdude239]

i work on these thing everyday and i have never seena coil go out not say it isn't possible I'd change the plug wires if they haven't been changed. did u use platinum plugs when you changed them i know the newer vehicles use platinum plugs and don't really like anything else. plus plug wires should be changed with the plugs

[fxdxharley]

Originally Posted by truckdude239

i work on these thing everyday and i have never seena coil go out not say it isn't possible I'd change the plug wires if they haven't been changed. did u use platinum plugs when you changed them i know the newer vehicles use platinum plugs and don't really like anything else. plus plug wires should be changed with the plugs

Not sure what plugs i put in there. dont remember. might have been bosh platinums. that was two yrs ago. you'd think i would remember being i just had them all out when i had the top end off. plug wires this w/e for sure. Thanks for the imput guys!!!

[bighaas79]

Originally Posted by fxdxharley

Not sure what plugs i put in there. dont remember. might have been bosh platinums. that was two yrs ago. you'd think i would remember being i just had them all out when i had the top end off. plug wires this w/e for sure. Thanks for the imput guys!!!

Not saying that the plugs are your problem but I will not use bosch plugs. I have never had anything but problems with them. Just my experience tho.

[fxdxharley]

well finally got around to replacing the plug wires. she runs a little better but still has the hesitation and little stumble. im thinking its fuel related now. IDK! Going to pull the tb and clean it again and check the idle control valve to see if its sticking etc. any other ideas you guys can think of would be great.

[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.

[Shon]

I just figured out mine....I tested the injector harness and was getting the noid light to light up but it was obvisous the cylinder was not firing, header tubes were 'cold'.
ended up having 4 of the 8 injectors not firing, I replaced those not squirting with spare ones and it runs good now.

I pulled the fuel rail up and had my son turn the key and watch to see what injectors are firing. and replaced them and run test again. it can be a little mess so you might take a little more time and catch the fuel being squirted out....