teaspoon

I am having a weird issue that I am not sure what is causing it or even if its normal. Any time there is any sharp throttle input the car goes into Open Loop, even on idle. If you slowly push the gas (super slowly) it stays in closed loop but anything else the STFT goes to 0. On HPT it shows 0 stft and on Torque it shows that the car is in Open Loop. So on a Wot Pull 75 percent of the pull the STFT is stuck at 0 (Open Loop) and then it goes to +-4 and holds there. Then shift and it does it all over again, even on cruise. Could be holding steady at 35mph +2 STFT and just stab the throttle and 0 SFTF and stays there for a few seconds. I have seen this kind of Fuel error before but on extreme Fuel trims. A friend of mine has a sky and his is at +-10 STFT at the moment and it does not have this open loop, closed loop behavior.
It has no codes and I have no clue what is causing this. I tried the stock tune and various tunes I found on HPTuners and nothing it does it on all of them. Also disconnected the Maf and drove it around to see if the maf was causing the issue. However it still had the same behavior. Now this car is tuned so when the trims get stuck at 0 the fuel does not go super lean or rich. However we found this issue before installing Opel injectors and running e85 (LT4 pump). We held off until we can figure this out because without trims and no ve tables we cant really tune it.

Any Ideas?

T-Man

iTrader: (3)

When is the last time you replaced the primary 02?

teaspoon

few months

teaspoon

I loaded the stock tune this morning with full write this time and checked all of the sensors. On the stock tune the issue happens less frequently but it still gets stuck on open loop on some sharp throttle inputs so not change. On any of the other files, it does it every time there is anything but the softest of inputs. I am not sure what is causing this but I ordered a new O2 sensor.

Henry3959

It's normal....

As far back as I can remember and that's to ECM feedback carburetors in 1980, the system ignores the O2 at 85% and higher. The computer is not necessarily going into open loop and will continue to say CL but the O2 is ignored in fuel enrichment mode.

1. Manufacturers do not have to meet emission standards above 85% throttle opening
2. you would not have any performance if the engine had to keep the A/F stoichiometric throughout the entire RPM range

Slowbalt2000

iTrader: (1)

source?

Henry3959

General Motors.... the 85% varies a little but not much.

Slowbalt2000

iTrader: (1)

Online source?

Henry3959

I have known this since I started training for GM as well as ATTP. Find an online source proving otherwise. This does not include diesels since the question was for a Cobalt I presume. If we had to meet the same government emission standards at WOT we currently have to meet we wouldn't have any muscle cars like we do now.

T-Man

iTrader: (3)

Do you have a relocated MAF? I know you mentioned you tried unplugging it and the issue still persisted but just curious...

Are you running 3 bar TMAPs? Have you had the throttle body off of the car and manually moved the blade?

Henry3959

Unplugging the MAF puts it in Speed Density which also operates the same at WOT. The O2 is ignored.
Think about it.... How could you get to your desired Power enrichment A/F if the PCM was allowed to trim what it was seeing?

ECaulk

iTrader: (6)

The LNF has a wideband and adjusts fuel trims at WOT. It's a torque based ecu so maf based at WOT not speed density.

Henry3959

Where does it get it's fuel trims from with the MAF unplugged?

T-Man

iTrader: (3)

The E69 ECU is always in closed loop (typically) under PE conditions or stoich/steady state. It's a closed loop, torque based system. We don't have loop control either. So if it's not staying in closed loop, there's an issue in the chain of feedback, which is why I asked about the MAP sensors and TB.

The question on the MAF relocation was out of shear curiosity.


The E69 enters into PE based on RPM, an average of requested pedal input versus actual ETC position and load. The car stays in closed loop, using primary 02 feedback.

T-Man

iTrader: (3)

ECU references the MAF frequency table, regardless of it being unplugged and will also reference the base correction table as well as others we don't have access to, with feedback from the primary o2.

Again, this is why I asked about the OPs primary o2 and MAP sensors.

Henry3959

Thanks... Don't have access to as not available in HP Tuner?
How well do they run with a failed MAF?

teaspoon

I tried failing the maf and using the maf correction table a a faux ve table on my old motor. The trims worked exactly the same without the maf, Yea it Worked as SD but i went back to the maf.

Now on my Trim issue, The maf is relocated to the cold pipe with a 3 inch section.
This is a brand new motor so the TB has been off the car and it does have 3 bar maps and using the old motors tune, so when the trims zero out it does not get dangerously lean or rich. I tried various tunes (scaling the maf) but no go on the trim issue.

ECaulk

iTrader: (6)

Have you taken a look at the maf data to verify that the signal isn't bouncing all over the place?

teaspoon

Attached is a screen shot of a stockish tune i was testing with this morning.

teaspoon

Loaded the stock tune again with the only changes this time is the Boost frequency table.
On the factory tune, the issue does not happen as frequently as you can see but its still there.

Thinking of replacing every sensor including the throttle body.

ECaulk

iTrader: (6)

It's hard to tell from a picture of the log session. But it looks like you're not keeping up with the desired fuel pressure, also I don't recall seeing you log the injector pulse width. It's also hard to tell without having access to the tune files you're using with a given log.

teaspoon

To add to this, Out of the blue it started missing and idling at max positive fuel trim and gave a code related to the brake booster and vacuum went to -24inhg. AFR went to 20+ at idle even with max fuel trim but I didn't have my laptop connected to see what the pump pressure was. Shut it off and just checked all the sensors, made no changes and it started up and drove it home no issues. So something is failing in there.

Hmm, it does have a Corvette pump in there.

ECaulk

iTrader: (6)

If you don't want your file and logs out there for anyone to just download PM me and I'll give you my email