Tacoma - OVTUNE - VFTUNER - Update Info and Original Development

It's hit or miss for me and I haven't been able to figure out what causes it. Occassionally startup is rough, or requires extra cranking. It doesn't seem to matter if it's hot/cold though.

When hot, sometimes the engine will fire and then immediately stumble which feels like a knock. It's really strange and not caused by the tune. It was there stock.

 

same. I've had a few odd balls, but its not consistent.

 

It is definitely worth testing, because the ECU will use almost primarily port injection at very low rpm when cold.
Then after the engine has warmed and only after it hits warmed up temp, it will switch to using DI only (except in some few conditions, like idle is still port).

I wouldn't be surprised if this is part of the cause. When the ECU runs on PORT ONLY, the AFR is much less consistent. I've only discovered this after individually logging each banks wideband results using LSU WBs without cats. Pair that with the fact the fuel pressure demand variable, there is a lot of inconsistency with AFR on Bank 2 (passenger side, Cylinders 1, 3 ,5)

Luckily I can flip only 2 bits in the ECU and turn the port injectors off entirely.

While I cannot *confirm* yet I think this has to due with the start up stratification request. Start up is primarily or majority port injection on full blast, and does a momentary dumping of fuel into the cylinders, and does not get any correction until the 02 sensors have come online.

 

turd vote on this one - but we are not getting many <40 degree days around here.

 

Its currently 1 here and feels like -15 if you want to come visit.

 

I am and I wasn't thinking fuel, but maybe I should? It rumbles at a light (in D, foot on brake), but is goes away when in N. It hasn't been a huge priority for me to track it down just yet.

 

I'm trying to think of why they would want to do that. Faster startup time and reduced cranking, eliminate a lean condition on startup?

 

To heat the cats up with fuel as fast as possible.

 

I did that tsb update a while back, engine still lopes @ ~1Hz on cold start (50* F garage) from time to time. If that's what you are referring to. Saw it before the tune, saw it with the tune still see it sometimes after I did the TSB. I've learned to live with it, though it is slightly embarrassing when the wife and friends ask, "wtf is wrong with your truck?"

 

as time goes on, it seems we could ask that about nearly everything Toyota did in the 3rd gen lol

 

Yeah, but that's after the engine actually starts. Why blast a ton of fuel into the cylinder as it's cranking?

 

To help start the engine. It's not uncommon actually to have big pulse widths during cranking, because you need the fuel to fire.
However watching this on my widebands on each bank, the AFR is all over the place.

it will never truly be perfect because the calibration uses 1995 method of closed loop.

But I'd like to test out on trucks that have this issue how they respond to PI disable on cold engine

 

I can’t say I’m Having any startup issues. If needed for a test guinea pig then I’d be glad to help any way I can just don’t think my truck is having any major issues here in Alabama while we’re having 60-70 degree days mid January. In about 3-5 days it’s gonna drop to highs in 40’s but nothing like the cold climates up north.

 

Anyone in the San Diego area (preferably north county Vista area) have experience with the install and setup? Got mine for Christmas and am ready to install but computers are my nemesis.

 

It's been -40 C here all week. No rough start ups / unsmooth engine idling. 2.0 BETA 4.88, 91 performance.

 

My engine has idle fluctuation when cold, although no startup issues. I’d say 50 rpm in both directions, enough to feel and see the needle bounce around. Can’t remember if it was there with stock tune or not, I’m on 2.0 19800 04a61.

 

I'm on Beta 2.0 with no start up or idling issue.

 

^^ Same as this with OEM calibration (04B41).

Once in a while (and this is very infrequent), the truck sounds and feels like it's going to die for a split second and then immediately sorts itself out. My '16 did the same thing.

 

I'll look at my data logs and compare misfire rate on this bank to other. I do recall cylinders 1,3 were seen quite often.
Thanks for looking into this.

 

@OVTune What would this do on a decatted dump tube exhaust? I think there are only about 6-10 of us out there but just curious? I have this occur quite often.