If the plugs are the correct ACDelco they are good for 100,000 miles.
I suggested checking the coolant level because grey smoke could be coolant burning/fouling the plugs.

 

I'm going to ask what might seem like irrelevant questions, but please try to answer all of them them anyway. I have first-hand experience with a problem that sounds very much like yours and it was solved in an unexpected way.

This sounds suspiciously like the rare ethanol sensing problem, except that there is no P0172.

Just to be sure, how are you checking for codes? Are you sure there is no pending code? You had the battery checked, so that would have cleared any pending or set codes.

You have a FlexFuel car allowing the use of E85, which is great stuff. Have you ever used it? Any chance someone put some in the tank?

Is it possible that the car is sometimes left running when fueling? Is a little extra fuel ever added after the pump stops automatically?

Have you ever noticed a fuel smell outside the car?

Does the car make a lot of short trips?

To confirm, does holding the pedal to the floor help with the hard starting? Does the gray smoke smell like fuel?

 

I have not checked for pending codes. There are none on the DIC. I will go to a parts store and have them check for pending codes.

I have never used E85 fuel but I can't be sure the previous owner didn't. I have owned the car 5 years without this issue.

The engine is always off when fueling and I do not add more fuel when the pump stops.

I have only noticed a fuel smell once outside the car but the windows are always closed so there may be other times that an odor was there.

Yes; the car is used for mostly short trips.

I have not had to hold the pedal to the floor to start the car. I only had to hold it down about 1/3 of the way to get it to start but the last few days I haven't had to touch the pedal to start the car. It still starts rough but smooths out quickly and runs great afterwards. It kind of seems slightly easier to start the first time in the morning and will start right up when the engine is warm. I put in a bottle of HEET with injector cleaner so maybe it's helping.

The gray smoke did smell like fuel. Not really a gasoline odor but more like what I would think ethanol might smell like.

The smoke is only present when I first start the car. When I start it several hours later there is no smoke but still the rough start.

I did check the coolant level and oil, The coolant level is a little low and the oil looks normal.

Thanks.

 

Did you clean the throttle body and replace the air filter, check the fuel pressure? I don't feel like scrolling back 4 pages.

 

Codes don’t show up on the DIC. You have to have a reader or scanner to pull codes.

 

I'm mystified as to why this isn't setting the check engine light. Most chain parts stores will scan for codes for free. WRITE DOWN THE CODES. THE NUMBERS, NOT THE DESCRIPTIONS. Ask them to also look for the stored ethanol %. They may not know what you're talking about, prolly no one asked before, but it's likely buried in the menus. DO NOT CLEAR ANY CODES.

 

I have not done these yet. I need to purchase a fuel pressure tester first. As I understand it the fuel rail must be relieved of pressure to do the test. What is the safest way to do that? I believe I must also disconnect the coils for the test too. How is that done?

As far as cleaning the throttle body it was mentioned not to operate the plate manually. So it must be opened with the accelerator pedal to clean, right?

I will get a new air filter too. Thanks.

 

Right, I meant the CEL was not illuminated.

 

As far as cleaning the throttle body it was mentioned not to operate the plate manually. So it must be opened with the accelerator pedal to clean, right? Right, do not try to open the throttle plate, the plastic gears strip very easily

 

I had the codes scanned today but didn't know I should ask about the ethanol%. There were no pending codes though.

Today on the first start it started up fine. No smoke or odor. Three hours later it was hard to start. I had to depress the accelerator a little to get it going then it ran just fine without any smoke or odor. I made a few stops after that and it started right up and ran great.

I will go back and have the ethanol% checked.