Truckingeek

Okay I might be going off topic here but to my understanding a cold engine will be in an "Open Loop" and therefor not using the o2 sensor to help adjust the fuel ratio at that moment. Thus the reason I was concerned with a temp sensor telling the ECM that the engine is warm/hot when in reality it is cold, thus when I just add a little fuel via the pedal it fires up right away and runs fine (as long as my foot is on the throttle). Once my engine is actually warm it will restart with no issues.

Step one for me is seeing if my scanner can read fuel trims.
Step two. If scanner can I shall read fuel trim in the mornings/or when I know the engine is cold. Then read them when engine has warmed up to normal temperature.
Step three. Compare the two.

Am I on the right track?

donbrew

As soon as the O2 sensors warm up it goes closed loop, about 2 minutes. Not based on coolant temp alone.
Your scanner should be able to tell if it is open or closed loop, and trims. I know Torque free does.

This is the generic explanation.


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Truckingeek

That's my point right there, as soon as the engine warms up everything runs fine. It only takes a minute or two. Just like back in the day if you tried starting an engine cold without pulling the choke. I must not be seeing the tree's for the forest.

cturboaddict

Car had sat for about 2 hours. Temp outside is around 35 degrees or so. Jumped in and started (hard start as usual, had to add a little pedal to ge it fired).
Scanned data
Fuel Alchol Content 41.68%
Long Term FT -17.19
Short Term fluctuated into negative double digits but stayed negative.

I reset the fuel trim and Fuel Alcohol Contet data.
Has been running for 1 min.
Fuel Alcohol Content 0.5%
Long Term FT -7.03
Short Term between -3 and positive 3

Coolant Temp data matches display.

Cat Man HHR

Listen to the video again.
With the STFT being in the negative % when cold it means you are running rich and the ECM is cutting gas back to get it back into the green zone on the video.
The -3% to +3% when warm is perfect.
The Long Term Fuel Trim (LTFT) is negative showing that the ECM over time has been pulling back on fuel to make the engine run leaner.
What gets me is the alcohol content %.
When cold it's about 42, that would be E42 gas. When warm it's .5% that's E .5 which can't be.
Have you cleaned the Throttle body and Mass Air sensor ?
Can you reset fuel trim and alcohol percentage with your scanner ?

cturboaddict

You must of missed it.
First read when cold. I let that run for 10 minutes with no change.

I reset fuel alcohol content and fuel trims.

then had the final results with the good alcohol content and fuel trims.

I'm about to double check it now that it has sat all evening. This is when the trouble always arrives.

DrLoch

The correction is based on the commanded fuel of the ECM. If it's a flex fuel car it has different tables that are based on alcohol content or perceived alcohol content. That being said the ECM thought the alcohol content was 41%. On top of that if the car is cold it will be in open loop, which makes adjustments to the commanded stoich AFR value based on coolant temperature.



Here are a couple of tables from a 2011 flex fuel 2.4 to show what I'm saying.

So the perceived alcohol content was ~42, based on that info the Stoich command would be say ~12.5 AFR (I don't feel like doing the math this morning). Now you take the open loop EQ ratio alcohol table and adjust the commanded by 12.5/1.75 (I picked the 1.75 value from the Open Loop EQ Ratio chart assuming a ECT of 46.4 and an IVT (Intake Valve Temp) of 46.4. so 12.5/1.75 says that commanded stoich valve should be 7.14 AFR. So if any of that info is wrong, which the content is, the ECM would be making adjustment to try and make it correct, in this case it was pulling fuel hence the negative fuel trims.

So, if the perceived alcohol content in the ECM is incorrect the fueling calculations will all be incorrect, car will run like crap.

Cat Man HHR

Dennis
Being that he first listed his alcohol % cold and hot I guessing at what you just posted made his cold start up problem ?
I understand there is no alcohol % sensor and it is derived from input values that the ECM equates into the % value.
If resetting that value and is recalculated there should be no issue with the cold start problem along with maintenance to throttle body and possibly the mass air sensor.

donbrew

Alcohol content is calculated from O2 sensor data. If the O2 sensor has not warmed up the data will be skewed (and ignored), that when it is open loop.

cturboaddict

GREAT INFO!!!
After restting the fuel trim and alcohol content last night- i drove the car for approx 15 min. PARKED CAR for the evening.
Went out this morning and IT STARTED WITH NO ISSUE. Turned the key and fired right up with no pedal assistance or stumbling upon firing.

I drove the car a bit further and the STFT and LTFT are acting appropriately.

Haven't seen LTFT get into any double digits, and mostey stays close to zero when idling at a stop.
The alcohol content has settled in around 5.1% now. (I also refueled).
The STFT will fluctuate between -13 and positive 10 while driving, but evens to around +\- 3 the most of the time.

There are no codes present (besides the TPMS i need to replace in the left rear tire).

I think resetting the alcohol content and fuel trim may have rectified the issue for now.