Hesitation after new muffler

SILVERADOSC540 · November 19, 2012

That could sure be part of it. That deal in the owner's manual that I think recall was related to some sort of anti-lock brake check I think. Did you look in your manual to see if I'm remembering this correctly?

scottmoyer · February 21, 2013

Just an update on this as I'm sure others will be looking for similar answers. I still have the issue and I've thrown more parts at the truck. I was reading on another site where many Silverados have had the fuel pump fail at around 120k+ miles. Since I now have 121k miles, I decided to replace the fuel pump and hoped that the filter was part of my problem. It wasn't! I still have the hesitation.

I did find one thing that I need to test further. I needed a special tool to release the fuel pump connectors, so my local Advance Auto set me up. I saw a sale on Lucas Fuel Treatment and decided to give that a try. Would you believe that the day after I used this, the hesitation was almost completely gone? The truck seemed to respond to throttle changes immediately, ran better and allowed me to actually spin the tires on takeoff. Having the 3.42 gears and the oversized tires, the truck has not been able to do this before now. I thought the issue was solved.

Not! I filled up the gas tank with Sunoco 87 octane and immediately noticed the hesitation was back. I bought some more of the Lucas stuff and the hesitation is almost gone again. Anybody have any suggestions on why this stuff seems to temorarily fix the problem? Next fill up will be with 93 octane to see what I get from that. If that fixes the issue, any suggestions for next on my purchase list?

Jennabear · February 21, 2013

Run a better quality higher octane, 89 would be fine. Gas a also currently in winter blend, so it is poor quality to begin with.

Sent from an ice cream sammich.

scottmoyer · March 25, 2013

Ok, I'm back with more updates. The truck still has hesitation and gas brands or octanes do not seem to help. I threw another part at the truck, which again I see a lot, and that was the throttle body. I put in a new GM throttle body, not an aftermarket one. The hesitation is about 1/2 what it used to be, but it's still there. I have no idea where to go with this but to continue throwing parts at it and replace all of the old junk. The dealer is worthless and wants to charge another diagnostic charge to find absolutely nothing, like they did before.

Anybody replace their gas pedal assembly sensor? I've read that some people have experienced issues where this was the problem, but in every case, their truck was in limp home mode, not just a temporary thing. The other thought I had was O2 sensors. Nothing is registering on tech tools so service departments and dealerships will only charge me to diagnose an issue that can't be duplicated. I may go back and redo the front and rear diff and transfer case fluids with the GM recommended stuff instead of the Lucas products I used. The issue started after this and it hasn't been found to be an electrical issue anywhere.

BigBlueLB756 · March 27, 2013

Here's an off the wall stab in the dark suggestion: Disconnect the battery negative cable for 15 minutes and then reattach it. Maybe computer gremlins are bumping into each other.

Remember, I said it was a stab in the dark.

scottmoyer · March 31, 2013

That stab in the dark was already done. Thanks. I disconnected the battery when I replced the throttle body in a hope that it would resync itself afterwards.

BigBlueLB756 · March 31, 2013

Since you said you replaced the throttle body, here's something TOTALLY off the wall, but since you're really miffed....

http://www.silveradosierra.com/vortec-5-3l-v8/grounding-wire-to-throttle-body-for-better-throttle-response-t15920-20.html

Who knows?

scottmoyer · April 9, 2013

Another update....I replaced the MAF this weekend and checked all the spark plugs. They are all good, and gapped at .040. The two injector fuses were also checked and verified to be good. The problem still exists. This is getting frustrating. The throttle response appears to be getting worse. Downshifting while attempting to pass has become very unpredictable. Sometimes the truck lags two to three seconds before it finally downshifts for passing. Until then, it just sounds mean, but goes nowhere. I wonder if my catalytic converter is clogged!!!

Jennabear · April 9, 2013

Do you have an AutoCal?

scottmoyer · April 9, 2013

No I don't. Will you guys be anywhere near Orlando in the near future? Come July, I may travel up to Minnesota, so if you are anywhere in-between then, I may look you up if this continues.

Jennabear · April 9, 2013

Nothing in FL. What year is your truck? We could possibly get a cable out to you to see if we see anything glaring.

I still think it is gas octane and quality, especially since you had positive results with additives.

Sent from an ice cream sammich.

scottmoyer · April 9, 2013

The truck is a 2006. I'm not really sure I had results with the additives. Have you heard of "hopeful thinking"? I need to get gas again today and I will fill it up with premium to see what happens. I'm thinking that my brain was telling me something similar to, "Hey, my truck runs smoother now that it's been waxed" rather than seeing the actual issues remain.

I will try to check the vacuum lines and the intake bolts tonight. I know there are a number of things that can cause this scenario that I still haven't touched, i.e. catalytic converter, O2 sensors, gas pedal sensor, ignition coil packs, computer.......

As with all the problems I've had with this truck, I know it will be something simple that I am just overlooking. I have 123k miles on this thing and haven't had any real issues with anything.

Jennabear · April 9, 2013

Try the higher octane again, I would also try from a different gas station. Quality might have been poor.

But if you are willing to put down a deposit, we can send a cable out your way.

scottmoyer · April 9, 2013

I verified that the intake is bolted down tight and I checked whatever vacuum lines I could find. The problem still exists.

Jenna, does Justin keep all tunes? If so, he should be able to compare the current settings to what he programmed before, right. I will let you know after the gas fillup. Thanks

Jennabear · April 9, 2013

Yep, he has all tunes. But he would want to see a datalog to see if anything stands out with how it is running now. He might be able to diagnose for you.