Michaellb1

Hi,

(This is long, bear with me)

So I just bought a 2011 Silverado 1500 LT / Z71 Crew Cab with 155K on it. It was a good deal for $13,995 very well maintained, approx. 60%-70% highway miles (I did some investigating). Was not used for work or serious load bearing.

It runs like new when driving at road speeds. Shifts a little hard but doesn't slip, transmission seems fine for it's age. No leaks noticed for any fluids. Truck starts right up.

Came with a fresh tranny fluid change, oil, coolant, powersteering fluid.

BUT

It runs a little rough at idle and in low gear, and seems to drop RPM slightly and raise up slightly and when in drive moving at about 2-3MPH it kind of jutts forward slightly. Now this is very minor, and likely would not be noticed to your average driver.

I thought maybe it was spark plugs, so I changed all 8. Plugs did not show serious signs of running rich/lean on any. But they were very worn, and WAY out of gap. I thought for sure this was the issue. But it actually got slightly worse.

I tried the old motor mount diagnosis by idling, feeling the rumbles, and seeing if they disappear when it's put into drive. The rumble stays exactly the same.

So I plugged my OBD2 in and checked the fuel pressure. It was running approx 42PSI for pressure when idling in park.

I'm thinking it may be that the fuel pump is starting to show it's age and miles, and is on it's way out.

I decided that given the age and high miles, the pump is bound to go soon anyways so I might as well replace it now.

Is this likely the issue? Has anyone else had this issue but found other resolutions? Just wondering where I should go next if this fix doesn't work for me.

Does 42PSI seem too low? I hear they should idle at between 55 and 60.

PS. It does NOT have a check engine light at this time.

Michaellb1

Thanks for the help guys -_-

Gumby22

If you’re not patient enough to wait more than a few hours for a response then you’re probably not patient enough to figure out what the problem is. Clearly everyone who looked at your post knows exactly what the problem is and just decided they didn’t want to help you.

42 PSI is too low - spec is 50-60 key on, engine off, and shouldn’t lose more than 5 PSI after 1 minute. If it does, the fuel pump should be replaced.

First you’ll want to verify its the pump and not the wiring. Your truck uses a fuel supply control module instead of a direct fused circuit with relay control and the modules (as well as most of the wiring at the rear of the truck) are known for having problems. The fuel control module is mounted on the frame near the spare tire - inspect it and the wiring for damage due to chafing, broken clips allowing the wiring to hang down, and corrosion.

If that’s all good, check the wiring at the fuel pump for battery voltage (gray wire) and a good ground (pink wire) - both with key on as it’s completely controlled through the module. If the power and ground are good, you can try a current draw test on the pump if you want, but most likely the pump is due.

PNW NBS Z71

I would also be concerned about cleaning the throttle body, plenty of you tube videos about that, and go to the parts store and get the MAP/MAF cleaner(s) and follow directions for cleaning them. They usually need replaced anytime after 100k miles so cleaning the MAP/MAF may not help.

Michaellb1

Dang, if you didn't have such a helpful response I would probably say you're an a$$h0le.

Thanks though.

Thought maybe I stumbled upon a forum that isn't really used anymore. I just joined and haven't had a chance to look around.

Either way, I appreciate you guys taking the time.

And yes, I am impatient. Patience is a virtue not a requirement!

PNW NBS Z71

When you die, it is your virtues that people will remember, not what was a requirement and shined on by you. When asking for help, not requiring it, it is best to realize that others have families and problems of their own. I bet you get the hang of it or regret it if you don't. Being in Vietnam taught me a lot about patience. I used to have none till I realized I was with a bunch of guys on the same carrier I was and they wanted to be home as much as I did but a job had to be done first.

Michaellb1

Who am I to argue with a Vietnam Veteran? Thank you for your service and for the words of wisdom as well!

PNW NBS Z71

Thanks

Gumby22

I understand how my words could come across as harsh, but it puzzles me to no end that someone can get on these boards and assume that the people on the other side of the screen have nothing better to do than wait for a new question to answer.

By far, there are more people looking for help than offering it, so the majority of the people who read your post were probably just curious or they were looking to see if your problem is identical to theirs and whether or not it was resolved so they might have an answer as well.

That said, I lean towards sarcasm, which is often mistaken for being an a-hole.

Thank you for your service. My uncle served in the Navy during Vietnam as well, working the engines on an aircraft carrier. I keep meaning to get more details from him (I don’t even know the name of the carrier) because it’s one of those things I don’t really think about when I see him unless someone else brings it up.

I mostly remember my dad always giving him a hard time about it because when my uncle was drafted, he was practically a twig. By the time he came home, he had a gut.

PNW NBS Z71

The USS Kitty Hawk was the second to last diesel powered carrier. CV-64 was the USS Constellation and the nuclear carriers started with CV-65, the USS Enterprise.