I finished installing my wideband and noticed something really funny... I'm super lean on startup (open loop) but once I hit closed loop it's back to normal. The AFR is good every startup after that unless I reset or reflash.

I thought in Open Loop it does not reference the short/long trims? It's learning something which corrects the AFR just not sure what.

Any ideas or suggestions?

ps. in closed loop my short term BLM's are at 130 and long term are at 160 & 144

 

my car idles real lean like 16+ but it it tuned that was so i dont shoot raw fuel from the tail pipe.

Jay

 

Do you still have a functional AIR pump?

Cold start or warm start? You can adjust the cold start A/F ratio enrichment.

In open loop, it uses the long term corrections (BLM's), just not the short terms (INT's), or the ability to learn. The fact you have such high long term corrections would indicate a flaw in the tuning, or a problem with low fuel pressure, faulty MAF readings, vacuum leak, exhaust leaks, etc.

 

No, no air pump. Also, this is on a single plane setup. Temp. doesn't really have an effect.

It has to be those long term BLM's. When reset to 128 that's when I have the lean issue.... no idea why?

It's a new fuel pressure regulator set at 43 psi (no vacuum). New o2's. Fixed the one collector leak and that fixed the short term BLM split. I'm sure there are no vacuum leaks but I will check again. I'll clean the MAF as well.
Maybe those SVO 30lb injectors are not flowing like they should.
As for the tune if anyone wants to take a look at an idle log let me know. The injector constant is at 31.73 and haven't touched the offsets.

I'll play around with it tomorrow.

 

From my experience the Lterms infact modify open loop fuel, so as you drive in open loop after a closed loop session, open loop fueling is modified by the old Ltemrs which were stored.

I think this because I have one of those cams that just make a mess out of driveability when in closed loop, the more I drive it the more surging I get, the less crispness in the lower RPM range, etc.

Because of this it was very easy to see a relationship between closed loop and open loop, and that relationship was every time I re-flashed or reset the PCM, the first few miles were the the best miles, every mile after closed loop was slightly worse and carried over into open loop as long as there wasnt a reset or a re-flash.

I did notice the open loop portions following startup were not as bad as the full closed loop portions, but still open loop was being degraded and I think it's due to the Lterms since nothing else stores learned fuel trims.

Nowadays since I completely disabled closed loop altogether the car is always completly responsive and always runs the same no matter how long I drive it and all on the same tune with no resets or reflashes.

I thought about runnign closed loop again however this time disabling Lterms but never tried it, and not even sure that's possible.

 

That one long term is maxed out at 160.
If everything else is good (fuel pressure, vacuum/ post MAF leaks, injectors, MAF sensor, etc...), I would adjust the fuel injector constant till your long terms are dialed in at cruising rpm, this should bring idle close too. If you have to change it much from what it should be, you might still have another problem.

 

Not sure what you mean when you say "Also, this is on a single plane setup. Temp. doesn't really have an effect." The PCM has tables that richen the A/F mixture and adjust the idle speed based on coolant temp - cold start vs warm start. The type of intake manifold wouldn't have any affect on this. But, given your additional info on the first start conditions, this does not appear to be the source of the problem.

There is no question that the PCM uses the learned/stored long term corrections in open loop. It does.

If resetting the BLM's to 128 causes the lean condition on the first start after the reset, you have to search for the cause of the extreme elevations on the BLM's. When the "160" resets to "128", the injector pulse width is shortened to supply 20% less fuel than it was at 160. The side with "144" is supplying 11% less fuel. You have to find out why the BLM's are screwed up. That will solve your "first start after reset" problems.

And just for reference purposes, what are you calling "super lean" on the wide-band readings?

 

Sorry Injuneer, I was typing fast and it was late. As you guessed the temp & single plane thing were meant to be two seperate pieces of info

"super lean" = about 18-19 for the AFR

I definitely have some investigating to do!

Thanks for the help so far