So i was out retuning my car (92 EG hatch with B16A running S300 on a P28 ecu) after installing some new injector dynamics 1000cc injectors. The engine is fully built forged etc minus cams NA and running on E85 with a Walbro 255hp pump and stock rail with AEM AFPR set to 55psi base fuel pressure.

Anyway i had it in open loop and got my part throttle (cruising) and idle to almost perfect staying right around 14.7 AFR. I then proceeded to make a few tuning pulls in 3rd gear and got the WOT AFR's dialed in to 13.2 (where i want it) perfect to the point of only a few cells on the datalog showing +-1% rest being 0 (AEM UEGO input on ELD pin for logging). The pull was very strong and everything felt healthy and awesome.

So the problem is this, i got home and went inside to eat some food, got back outside and left home. Its cold out like 25* here typicle wisconsin so my idle was high like 1500 i just assumed it cooled off enough that it was still cold idling. Well once i reached operating temp the idle starting surging from 1200-1500 over and over... Its still in open loop. Then i noticed the AFR's... It was idling at 12.5 or so and cruising at 13.2 completely different from just 20 mins earlier when it was perfect. So i try going WOT and the AFR jumps to 10.9 for a sec then Leans out to 17.xx like WTF???? so i try WOT one more time and it stays steady at 11.9(way richer than was just hitting every single time) but i notice Vtec is not engaging like it should be (tried this 4 times to see it was not crossing over at all and felt like a dog).

This was all happening at normal operating temp. I just came back home and jumped on here to post this sense its totally pissing me off as to why it would do this.

Im sorry for not posting a log of this situation my laptop died after the tuning session was over. :roll:

 

Was your battery voltage fluctuating ?
Where do you have your wideband grounded to ?

It would be useful if you would keep logs of your tuning, then compare the logs with logs of the car acting up etc.

 

Thats a good possibility with the whole battery thing because i left my headlights on last night and had to be "jumped" to get home, plus my battery is literally at least 5 years old and somehow still alive lol. Although didnt think it would make that big of a change or make vtec not engage and screw it all up? Ive noticed it wont hit vtec until its operating temp too in mornings. Plus i have the dead times entered in correctly down to 8V so it should have stayed remotely close to what it was. Its like to me its kicking over into a retard mode and using some sort of limp maps or something. My map sensor wires were cut in the past so im thinking maybe one of those could have come loose as well or not making a full connection. Would sure help if i had a darn log of this crap.

If it does it when i start it in the morning ill have my laptop to take a log, i have a few from when it was normal saved.

 

So just an update to the thread, i figured out the issue after studying some datalogs. Happened to notice right when i would feel it "kick over" into this crappy running mode the coolant temp sensor would be going from around 180 to 107 which would go below the min temp i have set for vtec to engage and obviously be enriching the fuel as if it was still cold and trying to force a 1200-1500 idle on a hot engine using the cold idle parameters was causing it to surge for obvious reasons.

Long story short, bought a new sensor and solved all issues. I suppose for you cheapo's out there you could just zero out your coolant temp compensation tables and make all the idles 1000 and deal with a crappy running cold start lol.