SR20 Lean Condition

[wozrally]

Recently got a sr20. Drove 8 hours home and was a strong motor. Did a compression test at time of sale and 150 across the board.
Stock Motor, Stock Turbo, Stock pressure and vacuum.

Recently I have been leaning out at idle and at cruise according to aem wideband. I can definitely feel it too. Bogs, pops.

Under WOT my ratio is 11.3-12, decent,and builds the 7 psi.
I have good vacuum at idle. 18-20 inHg.
I have checked for any leaks and cannot find anything.
All my vacuum lines are good, my exhaust is good.
Fuel pressure is 40 psi. Grabbed my old walbro 255 and put it in too.
Only thing is a 1400 rpm idle that is wrong.
Injectors seem to fire as I removed them and they were all wet. And must be good if under WOT everything is okay? although there is pressure increase in the system under wot...

Have checked maf and its good. I switched with a buddys maf and still.
Have checkd tps and it seemed that was the problem at first as we moved it and saw it would richen up, idle would move too. We switched to his and was good for a ride back to his house. Was at 13.2 f/r at 1300 rpm. It then started leaning out again. Only thing is, it was set to .56 ohms and wot was 10.1ohms! This was the case for both tps. And his car has been running strong. My original set was .8 ohms....

We unplugged the maf and it riched out. Plugged back and leans out.
we unplugged the iacv and it really made no difference. It should have?
The screw it turned all the way down and still very lean.

I was very scared to run all the way home at this lean condition, so therefore I would rapidly gas a tad and let out in order to throw gas into it. I would run rich 12-13 like this but I would buck it all way home.

At times, it really bogs out to 600-800 rpm, vacumm to about 12in hg and is lean. Then kicks back up to 1400 rpm at 13-14 f/r.

Right now I can only leans towards the tps and iacv as they were the only parts to make any difference when altered and a leak I possibly cannot find but doesnt explain the good build up of pressure and vacuum.

Removing iacv today.

Ive searched the forums. No thread really gives a final answer that I could fall under.

ah yes I pulled the E5 ecu but no light to read codes off. No bulb no nothing.

[Hijacker]

use the check engine light to read the e5.

As for the lean condition, you've done a good job running the easy to check stuff. Try swapping for a known good ECU and see if the issue persists. I just get a feeling it could be a faulty ECU with a corrupted fuel map.

[wozrally]

OK, Will use CEL light. Although right now no CEL.

If it is ecu, I guess I just dont understand how it could trip. Then be okay for a little and give out again. This gives a reason to believe it would be something wiggling or a sensor giving out...

I forgot to mention..This something happened 3 days before. I changed fuel filter and coincidentally , it was fine after.

All this happened, coincidentally, after going over a gnarly speed bump. At this time I feared a pinched a line but that wasnt the case....

[PyR0NiAk]

jumpy idle/leaning out is typically a preturbo/post maf vacuum leak.

I'd almost bet the bump jarred where your intake connects to the turbo. My IACV is deleted, so I can't help you there... The TPS is OFTEN blamed when it isn't at fault.

[wozrally]

No leaks...that I can find. Im going to blow smoke into on the of the lines and see.

But everything is tighten down.

Yes I do believe tps is good but funny how it "fixed itself" after I readjusted it.
and then 30 min later..its starts again.

Since it is lean, vacuum can only be part of the answer but all my lines are good.

Pyroniak, can you point me to how to delete the iacv ?

I know for my GSX I had a plate that covered it up, Also a few others would put the putty that solidifies at its port.

[PyR0NiAk]

I had a local shop when I was still stationed in NC make a plate that fit where the IACV bolted to my intake, used some gasket maker and bolted it down. You'll have to adjust the stop screw on your throttle body to adjust your idle, and it will do the opposite of normal with temperature. As the motor gets warmer, the idle will rise. (I set mine to 1k so it'll idle at 800 when cold)

And how would vacuum only be part of the answer? When my intake separated from my turbo, my idle jumped to 14.5 and would drop to 400, and that's without an IACV making dumb corrections. Post maf - pre turbo leak means the turbo sucks in unmetered air.

(I would never use a putty to clog a port. Picture a piece of it breaking off and going into the intake.)

[wozrally]

Yes I understand a vacuum leak. Right, unmetered air into to the cylinders would cause lean condition.

But I say only part because a leak creating this big of a problem, I feel definitely would have found it. Furthermore, I am still gettin 18-20inHG in vac.

It all points to IACV to me right now...just need to get home from work!

[Hijacker]

If you had a leak somewhere in the intake system, you should be running rich under boost though. Any leak that allows air in at idle is going to let it out under pressure once it's been metered.

If the IACV has never been cleaned out, consider doing that before deleting it.

[wozrally]

Right. I would lean with a vac leak at idle, richen under boost.

Only thing is under Wot im getting good f/r. 11.5-12.3 and 7psi

Im finally pulling the iacv today... rain -__________-

[PyR0NiAk]

Your theory about rich under boost is false. If it's post maf and pre turbo, it'll always be lean, and actually become so lean under boost you'll likely hit a fuel cut if you stay at wot too long. The fact you're not doing that, though, does dismiss that possibility. Your problem, does, in fact seem more IACV related. On a side note, deleting the IACV does also, as a side effect, delete the "bog" you get on dethrottle when you run an atmospheric BOV.

[wozrally]

I believe your incorrect. No theory, I know this from my previous car.

At idle a leak hole would pull in air due to high vacuum values and having more air than gas to compensate you run lean.
Under pressure the same "hole" would leak out air as it is under pressure. Therefore, since air is escaping, you will have more gas into the cylinder..running rich. This is for a hole in the intake.

[PyR0NiAk]

That air wouldn't be under pressure if it's before the turbo inlet... The turbo inlet will use that hole as another place to pull air instead of just from the intake.. I've been through it multiple times where I'm using a stock intake on my GT3071R with a step coupler (2.5" to 3")...



Excuse my paint skills, but they should further explain my point to help you understand where the leak is I'm talking about.

[wozrally]

ah yes before before turbo is right. Missed that. Make sure you get a good clamp!
But Im all good there.
After turbo, what I was thinking, what i said falls into place.

[PyR0NiAk]

Of course... Post turbo, you'll lose previously metered air.

[wozrally]

yep yep!
I do hope its this iacv.
I was messing with the tps yesterday after the rain and at one position, Idle nicely with 13.5 f/r but I cant rev it up as it leans barely touching the gas. This was closer to the spec'd resistance of .45kohm
At another position (.6kohm) Im leaning at idle (most of the time, it will be nice and rich all of a sudden) but able to rev it up as it richens up

[PyR0NiAk]

I chased IACV issues for 2 months before finally deleting mine. (Even resorted to ordering another used one...) I'm not saying delete it because some people swear by them, but I like keeping things simple, and removing the IACV simplifies things by a lot. I also run an atmospheric BOV, and deleting the IACV and having my throttle plate stuck partially open using the stop screw, causes there to never be that moment of your engine starving for air and bogging.