95 LT-1 Idle Cell Comparison - Humidity?

[spfautsch]

I haven't checked hot lash yet, but I doubt I'm losing compression here. Primarily because it acted the same way with hyrdraulic lifters, but also because lash has probably not shrunk during break-in, rather increased.

Startup fueling is getting my complete attention now, as is injector flow constant. I'll report back tomorrow once it cools completely.

Trust me - I've read "the gospel" on modified injectors and couldn't agree more, but I ran these injectors enough when the engine was a 5.7L to know they aren't the problem. If anything increasing displacement should have made them less problematic for startup and idle scenarios.

Thanks for your thoughts nonetheless.

[steveo]

just for fun lets force your IAC into operating range. crack the throttle plates open until cold start yeilds iac counts <160 and see if things improve. the air will be less even than a properly sized idle passage but that shouldn't affect startup too much.

More fuel isn't generally the direction I felt it needed to go when it smells so obscenely rich as it is.

it takes a lot for it to 'smell' rich. often a 'fuel' smell is a misfire due... lean will hit a misfire state more easily than rich

[spfautsch]

I'll try that if things aren't improved today. I actually tapped my throttle body to take a 1/4 pipe plug that I'm drilling to make different sized bypass orifices. 1/4" is the largest orifice I can create with the hex socket drive plugs I currently have. Yesterday evening I had a fairly successful start from 38C. IAC was pegged at 160 for the first few minutes but it was at least able to make the target rpm. I was really hoping to hear from someone who's done a 383 LT-1 in a climate that sees swamp-a$$ type humidity like St Louis. Houston, TX and the Carolinas are the only other areas I've been to with comparable humidty.

I didn't want to hear the word "misfire". That points me back in the direction of the ignition controller.

I would completely drop the humidity idea if I didn't also have a problem with my daily driver - a 1.9L turbo diesel at this same time. The vane actuator pot was worn causing the ecu to lose control at higher rpm and go into limp mode where it would command minimum boost all the time. The difference between a 90hp engine trying to climb a moderate incline with little or no boost in May versus July humidity was immense. In 95F air I could very plainly feel the "boost" from drafting semis.

[steveo]

so the only difference between the two snapshots above was humidity? no other engine modifications?

[spfautsch]

no other engine modifications?

There were - solid lifters and larger IAC bypass holes. But this problem started as soon as it started to get hot & humid, well before any modifications. Nothing really changed with the addition of the lifters.

Cracking the throttle a bit made a huge difference. The MAF was actually registering slightly less airflow at the same engine speed. I'm working on checking hot valve lash so can't post too many details. Will try a cold start in the morning and post an update.

[Rocko350]

You're at the point where you need to enlarge the idle passages in the intake manifold.

[spfautsch]

You're at the point where you need to enlarge the idle passages in the intake manifold.

Anyone have a second on this opinion? I'm thinking the same but damned if I didn't just put the manifold back on 3 weeks ago.

What would baro tell me about? I thought $EE only uses SD if the MAF stops working.

[spfautsch]

Here's a short log of a drive this afternoon. In general it's not running very impressively, but as I've mentioned the transition to closed loop was unnoticeable if that means anything. I noticed some popping in the exhaust when decelerating from a few PE "events".

I suspect that the humidity is causing the MAF to register inflated airflow #s. I say this because I've always logged less spark knock in humid conditions, and I'm presuming that's caused by the water vapor increasing the cooling effect on hot / heated parts. I haven't tried swapping to SD mode yet but will if I can get it to start and stay running reliably.

Wideband is a LC-2 on D27 using default settings. I'm not sure how meaningful any of the data is except to use for cylinder balance testing. I pay it almost no attention unless I drive the car a few minutes to get the exhaust hot. Even then, Missouri's laws on ethanol are stupid - it's considered required in some concentration but they don't have to tell you how much or that it's even present. I'm guessing the 93 octane I'm running has a stoich about 14.5:1.

By the way, with the help of a definition file I found in kur4o's build folder I found I could display the wideband units in Lambda with this in the definition.csv:

54,WIDEBAND_D27,Wideband O2 @ Pin D27,^,EXTENDED,8,2,0.007874016,,0x01,0xFF,,,,,

[Rocko350]

Here's a short log of a drive this afternoon. In general it's not running very impressively, but as I've mentioned the transition to closed loop was unnoticeable if that means anything. I noticed some popping in the exhaust when decelerating from a few PE "events".

I suspect that the humidity is causing the MAF to register inflated airflow #s. I say this because I've always logged less spark knock in humid conditions, and I'm presuming that's caused by the water vapor increasing the cooling effect on hot / heated parts. I haven't tried swapping to SD mode yet but will if I can get it to start and stay running reliably.

Wideband is a LC-2 on D27 using default settings. I'm not sure how meaningful any of the data is except to use for cylinder balance testing. I pay it almost no attention unless I drive the car a few minutes to get the exhaust hot. Even then, Missouri's laws on ethanol are stupid - it's considered required in some concentration but they don't have to tell you how much or that it's even present. I'm guessing the 93 octane I'm running has a stoich about 14.5:1.

By the way, with the help of a definition file I found in kur4o's build folder I found I could display the wideband units in Lambda with this in the definition.csv:

54,WIDEBAND_D27,Wideband O2 @ Pin D27,^,EXTENDED,8,2,0.007874016,,0x01,0xFF,,,,,

Your phone have a baro sensor built in or have you checked local baro reading from weather bug or another trusted source and see if your within 3 kpa of reported. If it was humidity related, a smaller plug gap would yield a driveability improvement. Wide band would report a richer mix also if the MAF was over reporting due to increased air mass from the humidity. startup ve is usually about 60% of normal VE.

[Rocko350]

Here's a short log of a drive this afternoon. In general it's not running very impressively, but as I've mentioned the transition to closed loop was unnoticeable if that means anything. I noticed some popping in the exhaust when decelerating from a few PE "events".

I suspect that the humidity is causing the MAF to register inflated airflow #s. I say this because I've always logged less spark knock in humid conditions, and I'm presuming that's caused by the water vapor increasing the cooling effect on hot / heated parts. I haven't tried swapping to SD mode yet but will if I can get it to start and stay running reliably.

Wideband is a LC-2 on D27 using default settings. I'm not sure how meaningful any of the data is except to use for cylinder balance testing. I pay it almost no attention unless I drive the car a few minutes to get the exhaust hot. Even then, Missouri's laws on ethanol are stupid - it's considered required in some concentration but they don't have to tell you how much or that it's even present. I'm guessing the 93 octane I'm running has a stoich about 14.5:1.

By the way, with the help of a definition file I found in kur4o's build folder I found I could display the wideband units in Lambda with this in the definition.csv:

54,WIDEBAND_D27,Wideband O2 @ Pin D27,^,EXTENDED,8,2,0.007874016,,0x01,0xFF,,,,,

Your phone have a baro sensor built in or have you checked local baro reading from weather bug or another trusted source and see if your within 3 kpa of reported. If it was humidity related, a smaller plug gap would yield a driveability improvement. Wide band would report a richer mix also if the MAF was over reporting due to increased air mass from the humidity. startup ve is usually about 60% of normal VE.