Running SUPER lean

[Tommio RS]

Ok so here is my sort of problem i have been having off and on.

So my car has a Rob tuned 550 ecu in it.
All supporting mods other than fuel pump. I tell ya why is a sec.

Now here is what she does.

IF it rains outside like the night before sometimes the car runs DAM lean for a while.

The AFR will just creep higher and higher then run like CRAP for about 10mins or so.

When she is GOOD and hot the AFR goes back to the normal like NOTHING happened?

Also it does NOT run lean instantly. Once the car starts to run in closed loop it will run like this?

Im thinking 4 things could be at fault:

IAC vavle issue?
02 sensor wiring getting wet?
Plugged fuel filter maybe/Dying fuel pump?
MAF issue?

I have NOT changed the stock pump for 2 reasons:

One the cars fuel tank it DONE! It leaks fast when it get about 3/4 full.
Im fear that tank damage is by where the fuel pump access hole is. So if i mess with it i will have to WAY to much work to fix it.

This car is really just a mule for my minty 93. I just want this issue fixed BEFORE swapping parts between cars!

Also i have a nice video i will show ya.

https://www.youtube.com/watch?v=UQJ88HPNqXk

Thoughts??

[lucas]

Just a shot in the dark and i have no knowledge of robtune, could it have something to do with your altitude and the limitations of mass air flow and such? Just an idea maybe you can spit ball off that.

[Legacy777]

I'm assuming your AFR gauge is utilizing a wide band O2 sensor?

Does the lean condition only occurr at start up? Does it occur while driving as well as idling?

Assuming the problem completely goes away when the engine has reached normal temperature, I would ask the question; when was the last time you replaced the coolant temp sensor?

[Tommio RS]

Lol i knew Legacy 777 you would ask the old coolant temp sensor question!

Probably about.....4-7 years ago. It could very well be going out the door.

I would of loved to hook up the old ssm and check out all the data. I know when the CTS failed on the other 2 leggy SS, the car would run like CRAP all the time until hot. Also the sensor on the ssm would read -40 ALL the time.

The AFR gauge is hooked up with a wide band yes. Nothing to do with the ecm at all.

Does the lean condition only occurr at start up? Does it occur while driving as well as idling?

The car runs perfect until it enter closed loop. The moment the cars temp gauge comes off the bottom it does that lean dance..... Then when "Warm" goes away.

The more i keep thinking about it, it sounds more and more like a CTS......

[Legacy777]

Unplug the O2 sensor to keep the car from going into closed loop and see how it runs.

If the CTS is bad, it will still likely run poorly since the CTS affects the fuel mapping and fuel enrichments.

[Tommio RS]

Good idea Legacy777! Will do if that happens again.

I have been driving it solid for about a week and it HAS NOT done that lean dance once!!!!

WTF!!!!

If it does i know what ill do!

[jefferson]

I think you have an issue with the moisture getting in something and messing things up. When the engine gets hot it dries the moisture out and it runs ok. I have seen it happen before on really humid mornings or after a rain.

[Tommio RS]

jefferson I think you are right. I know from exp. that many new subaru suffer from this. Mainly in the interior of the car.

So for know im just going to blame some moisture getting some where.

Although there is still a million other things that could be out!

[Tommio RS]

Well it did the lean dance AGAIN but i was not driving the car at the time....... Never got to unplugging the 02 sensor......

But yet again it cleared itself up and has not messed up since.....

Now here's the problem im having here.

IF its a faulty CTS why would it not throw a CEL? The past 2 leggy SS i have had came to me with bad CTS and the CEL on for just that. Car ran like crap ALL the time untill fully hot. Just like my problem right now.

So im have problems just understanding why its soo intermittent?

Also my other problem is.....I have no why of reading the engines data stream.....
I am a tech by trade so i know EXACTLY what im looking for when i see this sort of behaviors.

I have tried the following devices on it to try and read the data:
SSM
SSMII
SSMIII

So do i just need to get like EVO scan or something??

If thats my answer to scan a Rob tuned ECU let me know!
Give me a link or something!


I really what this fixed!

When the car enters this mod you have no choice but to pull over and sit there reving the car to keep it from dye or running extreme lean.


Thanks!


Tom

[nosyt]

my car ran lean with stock pump and 550 tune. switching to a walbro fixed that issue instantly

[Legacy777]

Tom,

Regarding the CTS not throwing a code....I've seen/read that it happens. My personal opinion is that this happens because the ECU logic is not smart and most of the time the temp sensor fails within the extremity bound limits. This wouldn't necessarily explain the intermittent nature. That could be related to a wiring issue.

As for reading the data streams, I believe you need the EVO scan program. I could have swore there was a blurb about it in the Robtuned thread or in the electrical forum.