Truck vibrates at idle

kevin79 · April 19, 2017

I have a 2009 Sierra that will sometimes vibrate at idle (like the engine isn't getting gas) and the RPM's will fluctuate, not a lit though, maybe by 50-100 RPM. The RPM's don't seem to fluctuate during driving but I'm not positive. Any idea what to look at?

O_J_Simpson · April 19, 2017

Look at your odometer. How many miles are on it?

kevin79 · April 19, 2017

Just over 157,000. I just bought it used when it had 155,000 miles. I had the transmission fluid flushed, transmission filter changed, coolant flushed, power steering flush, brake fluid flush, front and rear differential flushed, the dealer also changed the oil before I purchased.

I don't have any history on the truck.

The u-joints and brakes were also check and are good. There is a K&N air filter too. I plan to clean that this week.

redneckgames · April 19, 2017

My dad's 08 Sierra does the same thing with 98k miles on it. At a stop light it feels like it has a miss to it. Drives fine though and averages 18 mpg which is great around there.

Recently I had to drive the truck on a 2 hour trip. At first I had forgot about the surging and it alarmed me, then I remembered it was normal. Towards the end of the trip I had a trouble code show up. I asked dad if he had noticed the light being on to which he replied "Ah it comes on at times, but still drives good and gets good gas mileage, Im not too worried" Well I pulled the code and it was a Cylinder #1 misfire. I cleared the code and it didn't come back on the 2 hour trip back. But Im beginning to wonder if plugs were ever replaced in that truck and if it was causing the stoplight hesitation/miss.

Not much help for you, but Im interested in the fix and maybe we can help each other figure it all out.

kevin79 · April 20, 2017

I'm not sure if the spark plugs were ever replaced. I'll try that and see if it helps any. I'll update this thread after.

Bad Bowtie2 · April 20, 2017

I would definitely replace the spark plugs and wires with that many miles. New AC Delco ones.

Spring for new AC Delco upper O2 sensors too, when you have the extra $.

O_J_Simpson · April 20, 2017

With that many miles plugs and wires are in order. Go OEM.

kevin79 · April 21, 2017

Ok, stupid question but what do you mean by wires?

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muddkatt · April 21, 2017

The wire that connects to the spark plug and connects to the coils. They are about the same diameter as a pencil.

kevin79 · April 24, 2017

How much should I expect to pay to have the spark plugs replaced?

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redneckgames · April 26, 2017

Go to rockauto, buy a set of AC Delco Platinum plugs and a set of wires. Spend about $40 (maybe 60, I don't remember). Replace them yourself in about 30 minutes. All you need is a spark plug socket, 3/8 ratchet, and a short extension.

kevin79 · April 27, 2017

Go to rockauto, buy a set of AC Delco Platinum plugs and a set of wires. Spend about $40 (maybe 60, I don't remember). Replace them yourself in about 30 minutes. All you need is a spark plug socket, 3/8 ratchet, and a short extension.

Would Iridium plugs work?