marktigerz

I took my car out for the first time for a long drive since November. I suddenly realized the engine is rough at idle. It hesitates and sputters when you push hard on the accelerator. There is no CEL though. the tank was almost empty with the low fuel indicator having just come on. I put a fresh tank of 93 octane gas. I poured a bottle of octane booster and a bottle of rislone gas fuel system cleaner

I have driven it now for about 10 miles and it is doing the same thing...What should I do? Is it the gas in the fuel tank gone bad? when I had my car garaged in the winter - about 5 months - I used to start it every 7-10 days and run the engine at idle for about 15 minutes (Just so the battery does not die).


Any help or suggestions are much appreciated

slief

I'd put some miles on it and see if it settles down. Could just be some bad gas or water in the tank. My guess is that the latter as your car has been sitting for in excess of 4 months. I've always stored my boats with the tanks full and use fuel stabilizer in them. Water accumulates in fuel tanks when they sit and the less fuel you have the more water accumulates. Water also settles to the bottom so it's likely you are burning some water which could cause the rough idle. I get on the highway and run some gas through it. I'm betting after a tank or so through it, it should smooth out. You could also run some fuel system cleaner through it too.

bigblock427

NSC5

And ethanol makes it worse, very hygroscopic and gums things up. I made the mistake of using ethanol cut gas the last time I used my chainsaw and even though I also had stabilizer in the fuel I still had to clean the carb to get it back to idling smoothly.

87 octane is the only ethanol free still available in this area and I normally use it for all my non-diesel outdoor equipment but I got lazy last fall. I learned my lesson.

I would run a couple of tanks through your C7 before taking it to the dealer, hopefully it will clear itself up.

mksz51

Agree with all of above. Finally - purchase a battery maintainer and discontinue letting your car idle for 15 minutes periodically. That is NOT good for it, never allows the engine to REALLY warm up, and just creates and promotes moisture everywhere (crankcase, exhaust system, etc.). If you can't drive it just let it sit and don't start it.

stvaughn

And keep the gas tank full.

marktigerz

Thank you all. I hope she is just having a viral cold and I hope she gets better real soon

Shodanusmc

Agree, Sta-Bil in the tank (full) and a battery tender. I used to just throw in a bottle of rubbing alcohol 90% Isopropyl alcohol in the tank.

ENCT

AZstingray

Does it make kind of a rattling sound at idle? It might br the torque tube/driva shaft bearing problem I had. Apparently it is common. I took it to the dealership and they diagnosed the problem.
They replaced the torque tube and now my car is quieter on idle and running really smooth.

marktigerz

Not sure if there is a rattling sound...how loud ? I ask because sometimes if I listen really carefully there is a very faint rattle I heat but it was like this from day one...It actually sounds more like a fluid movement. Was there a CEL with yours?

AZstingray

No I didnt have a check engine light.

ATX-C7

If I turn off radio and listen (inside with doors closed) I hear this 'fluid movement' sound as well. It's weird, but I assume normal?

marktigerz

UPDATE

Since my last message, car kept running rough at idle with frequent hiccups or what I can best describe them as mini "misfires". This was still the case after going through three tanks of high quality 93 octane gas. In addition, I also started noticing a peculiar engine "metalic ticking" sound most pronounced at 2500 RPM.

I dropped the car off at the dealer to get it checked out. Codes were clear with no misfires registered. Upon inspection, I am told the engine roughness is normal for that kind of engine (Normal? really? ...I said this was not how it ran when I first picked up the car). They said the engine tick however is definitely NOT normal.

The next day I received a call. They ran the engine next to a brand new car that was just delivered for a customer. They said both engines had that rough idling feel and insisted again that it is not abnormal.

Now the bigger issue. They still can not figure out the engine tick noise. GM instructed them to check the rocker arm which they did and it looked fine.

3 days now and final word is that GM is sending in an engineer to try to diagnose the problem

In the meantime, I am stuck with a 2014 loaner Impala....and it is actually growing on me .....(Kidding kidding kidding...I miss my corvette)

gthal

Very sorry to hear this. The rough idle is generally a characteristic of the engine and reportedly designed that way. A light ticking sound is also a characteristic of a DI engine. However, a loud or obtrusive ticking is a sign of a bigger problem... I would have thought the rocker arm (based on another member with a similar problem) but will be interested to know what they find.

Hopefully you are fixed and back on the road soon!!

KenHorse

Z51? Oil moving from the reservoir to the engine and back

-CM-

Normal.

runutzzzzz

My car ticks pretty loud, it's coming from the drivers side bottom, can't really hear it from the top. My dealer says it's normal.

HummelS

One member reported similar symptoms that were ultimately traced to a loose plug wire. My C7 does not hesitate when I mash the "go" pedal. It goes! It does not exhibit what I would consider to be a "rough" idle - maybe a little on the "cammy" side, but not rough.

shaan

Its normal, mine does the same, I recorded a video of it to show it to the dealer and they still said its normal