Sounds like the Purge Solenoid, cheap and easy fix.

 

Im gonna say its perhaps the coolant sensor. Not the temperature sensor for the gauge, but the coolant sensor that sets how much fuel to add or NOT add when it's cold.
Is the money light on ?
Any codes stored ?

 

check engine light is on, has been on for over a year. took it to a couple different places and they kept telling him his gas cap was loose. We knew it wasn't. I did buy a new gas cap too but the light came back on repeatedly. Don't have a code reader. Need him to take it to auto store to get the code read. He's working long hours right now and hasn't had a chance to do this.

 

You may have more than one issue here. If you bought a Dorman gas cap I would not necessarily trust it. New from those guys means Never Ever Works. However. The vent purge valves at the tank are known to cause issues as is the one under the hood. However, neither will cause the issue your having....... I don't think.


Edit
Spelling. Dorman not Dormant

 

I did change the vent purge valve at the tank last year at recommendation of auto parts store after they read a code. Not sure if my “new gas cap” is a dormant? I ordered a basic code reader that should come tomorrow. Will update when we get a chance to look at it.

 

Got the code reader. Code is P0172 System to rich bank. Gas cap is not a dorman. The code reader has a "live" mode that reads a lot of other variables, most of which I don't understand. The care seems to run good after it starts. Even idles fine. I did clear the code just to see if it would come back right away and it took about 3 miles of driving and it was back on. found out it also pulls hard to the left. Have to turn the steering wheel quite a bit to the right just to drive straight! because of that the front left tire is worn uneven and very little tread left.

 

trying to figure out the other info on the reader. I think the long term fuel trim reading is not good at -25.0. short term fuel trim is -.8. Map is 29, MAF is 4.98..I'll try to upload some photos I took of the scanner readings at idle:

 

TP (%) at 21.2??? is that throttle position sensor? the car was idling?

 

At -25% fuel trim the computer thinks the engine is running extremely rich. But with the engine is running ok when warm I bet it's not running rich at all. Instead the PCM thinks it is due to it miss calculating the ethanol percentage in the fuel, and this is the one piece of information that the scan tool that your using isn't telling. Unfortunately a lot of non OEM scan tools do not tell you what the PCM thinks the percentage is, you will need a Tech2 or similar scan tool. Check the ethanol percentage and if it's greater than 10% (and it probably will be) you'll need to use the scan tool to reset that percentage. With a Tech2 the reset will be in the engine special functions menu.

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So something must cause this “miscalculation” of alcohol %. If I get it reset with the right scan tool, is it just going to happen again? Would a local auto parts store have the right scanner and be willing to reset it? Heading to autozone later to pick up oil and filter too as it is past due.

 

It's a software anomaly. It can happen again. In the 7 years and 150k miles of driving that I have owned my '08 Impala this miss calculation has only happened to me once and I do use E85 from time to time with no issues. The auto parts stores won't have a scan tool that is capable of doing a reset, disconnecting the battery won't reset this either. You'll have to take your vehicle to a Technician/mechanic that has a GM Tech2, Snap-on, OTC Genesis or other very expensive scan tool to do the reset.

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Here is a bit of an explanation. Eric from South Main Auto (an excellent YouTube channel) does a fix

Hope it helps. Its aGM issue.

 

^^^ great video and explanation

 

...ooops, posted too soon. I was going to ask if anyone knows for sure if these values can be reset by disconnecting the battery and touching the cables together for sure?

 

80% fuel composition

 

Apparently it has something to do with refueling habits. 10.00 20.00 at a time etc.

 

This is my sons car and this is exactly how he refuels. $10 or $20 at a time and runs it right down to Empty all the time.

 

I think Eric from South Main Auto addressed that in the video. Keith from New Level Auto has done a couple of vids on those recently as well. One an older Cadillac. It's apparently a GM thing especially in the older ones. There is evidently a "reflash" for some of them to solve this. Mine fortunately is a 2006 and did not have the Flex fuel or E85 feature. I don't miss it.

 

Never run anything other than 87 which has up to 10% ethanol in it here.