Thanks. Going to log it here soon.

 

Ok! After an entire hour of idling,the car finally stalled itself due to being too lean. And would not stay running upon a restart after this.

Started out at an average of 1.35 IPW. Then by the time it stalled IPW's were up to 1.6 average. I attribute the higher IPW to the higher fuel trims.

Fuel Trims started out at an average of -4 STFT. And -4 LTFT. By the end STFT was maxxed. For some reason LTFT's did not go active during the test. They usually do. But this is not my biggest concern at the moment.

To address some of the previous questions.

-Maf volts are steady between 1.4-1.5 pretty much the entire time. Not a MAF issue.
-Fuel pressure is stable at 38psi while running.

-I am going to look into Golden's theory of un-metered air getting in somewhere. Maybe this will show something. Not holding my breathe though.

 

If your MAF has consistant voltage.... is it possible for it to have un-metered air getting in post warming-up? I would think in order for it to be a vacuum leak that develops as the car warms up you would notice a drop in voltage at the MAF correct?

Just my thoughs at first glance. Anxious to see if you figured anything out from today.

 

For the benefit of others:



So the STFT is keeping the AFR's at stoich.

Given the load isn't increasing and boost/vacuum isnt changing I have to assume it's not a mechanical issue...

Although I would have expected to see a relationship between IAT/MAT/ECT and STFT/IPW - which there doesn't appear to be...

Any chance you can run a CAI to the intake to see if its a IAT thing (vs MAT/ECT)

edit - Also the fact that the AFR isn't going rich or lean would suggest that the ECU is doing the RIGHT thing.. ie if the STFT didn't start drifting then the AFR would go lean... its not.. so extra air (or more dense air) is getting in and the ECU is adjusting for it...

 

The Primo Intake makes it pretty damn tight to get a CAI on, I'm guessing. Not much curve space left.

 

it doesn't need to be fancy, or hold on..

ie aircon duct!

just something you can put over the filter and run OUT of the car.. so the MAF doesn't get 150F temps...

its just a test to see if you get the bad behaviour with COLD air HOTAIR

 

I think the opposite. Beings that load did not change (i.e. the ECU did not measure any increase in air) and boost/vacuum didn't change (i.e. ECU did not measure any new air) it HAS to be a mechanical issue. The fact that increasing fuel DOES keep AFR perfectly at stoich means that air is getting in there somewhere.


I just thought of this... Does RPM increase at all during this? If more and more fuel is needed, which is obvious by the increase in IPW, then RPM should increase due to an increase in power. So... if RPM does not increase, it could be the injectors. Maybe the injectors are letting in less and less fuel as they heat up. Because if the air intake is constant (assumed by no increase in RPM) then it would be an issue with the fuel delivery. You could test this theory by idling the car with stock injectors.

Edit: One last thing... The IPW increased by 18%. That should increase the idling RPM by a ton if air is getting in. I'm leaning on the idea that fuel is not being delivered as the ECU thinks it is.

 

RPM isn't changing at all much... its definitely not increasing in any meaningful way.

and yeh I agree with your hypothesis that air is getting in at that certain temp OR the fuel isn't being delivered properly..

 

Do you see what I'm saying about adding in 18% more air and how it would increase RPM?

We do know that the AFR is a constant during this issue. That is why I now think it is a fuel issue.

 

yeah I dont know about increasing RPM...

Unfortunately TPS wasn't logged so we cant see the ECU pulling out Throttle to bring back the idle rpm...

I cant see the injectors doing anything wrong, they are pretty simple devices...

I guess it could be something like the intake manifold not tq'd down properly...

 

It's happening on two cars, built by different shops. Possible, but sort of makes it less likely.

How about the thought of fuel vaporization? Could the area be getting hot enough, manifold, fuel rail, etc, that fuel is vaporizes before it gets injected, causing it to then run lean? More fuel injected, gets vaporized due to heat.... etc etc.

I know my car does not have any thermal insulation around the manifold (ie, a manifold spacer) or between the fuel rail and the manifold.

I guess a bag of ice could be laid on the manifold/rail to keep it cold, but not impact the MAF temperatures at all.

Edit: I'm basically just saying what Sean/TheBigJones had mentioned to me, in talking to the tuner about the issue. The logic makes sense to us, but we're not tuners/car builders, just sort of spitting out ideas.

Second edit: FWIW, a LONG time back, like 2 months ago or something, when my car was still in the "build/post initial tune" stage, I drove it down (or rather, attempted to) to Atlanta/Tail of the Dragon, for a tune/fun drive. When stopping for lunch in Tennessee, after driving in the heat all day, and then driving around town, it did basically the same thing; went insanely lean, couldn't drive, ended up dying and not running correctly again. Ended up towing it home.

That was with a COMPLETELY different map, COMPLETELY different tuner, and most likely a much "richer" tune to begin with. So it's been an issue since the beginning of this build.

To me that points to more of a mechanical/heat issue than a "tuning" issue, since the map was massively different.

 

your cam sensor isn't in backwards is it?

 

"fuel is vaporizes before it gets injected"

Where would the fuel go? It's a closed system. If the fuel was vaporized before it hit the injectors, it would still be injected as fuel vapor. The fuel system is a self cooling system. I doubt it gets that hot.

 

Would this cause it to act up in the severe heat but not otherwise?

 

Could it be a fuel flow problem? Wouldn't the injectors stay open longer if the correct amount of fuel wasn't being delivered in the 'normal' time frame?

I think this is a lower probability as you're saying that the fuel pressure is remaining constant though...

Interesting that the IPW's start climbing just as the engine load settles down. Could be coincidence but that looks odd to me.