narrow-band A/F gauge is reading VERY lean after a series of mods/engine-bay cleaning
 

Anyways, the car in question is an 87.5 Turbo II. The important mods are:

~RA apex-seal rebuild w. 15k miles
~9:4:1 N/A rotors
~street-porting
~stock turbo w. ported WG
~full exhaust
~R-tek 1.7 chip
~Greddy Profec-B EBC
~Marren 750cc secondaries
~Walbro 255LPH fuel-pump
~etc.

Anyways, I just went through an extensive tear-down/engine bay cleanup that included the removal of the:

~A/C
~OMP setup
~FULL emissions removal/TB stripping
~installment of 2751 Engineering block-off plates
~redoing the engine-bay grounds
~redoing the fuel-lines
~replacing the fuel-injector O-rings
~replacing two broken wiring harness fuel-injector 'clips' (one primary, one secondary)
~replacing all of the leftover vac. lines
~replacing the stock turbo (with another stocker)
~installing a Thunderfab 80mm DP/MP in place of a 2.5" Bonez setup

Anyways, before I began the project the car drove and idled perfectly and my narrow-band Autometer A/F gauge would read a consistent 'STOICH' at idle and as the accelerator was pushed toward WOT, the reading would move into the 'RICH' area and stay their until redline at 7k RPM's.

Now, there's no need to debate the poor tuning ability of the narrow-band A/F gauges, but as a basic indicator, it did a wonderful job.

Since completing the project today and getting everything buttoned down completely, my idle has remained solid, my vac. pressure at idle has gotten better and overall the car is running wonderfully.

EXCEPT, I noticed that the A/F gauge is reading so lean that the red glowing "indicator dashes" are nearly invisible in daylight and *barely* visible at night. This is at idle, low throttle, WOT, past the secondary injectors kicking in--EVERYTHING. It just reads a faint and 'wavering' LEAN...

I'm worried, but I frankly don't understand. There are no vac. leaks, hence the wonderful vac. pressure at idle, no hesitations, it starts wonderfully with a solid idle etc... It's like, nothing is wrong AT ALL except for this worrisome gauge reading.

Now, I did have the O2 sesonor out for a couple days (wrapped gently in a plastic baggie) while the new DP/MP setup was waiting to be installed AND the wiring for the A/F gauge's "splice point" into the 'O2 sensor wire' is pretty hokey, but it's always worked unfailingly before these modifications...

Anyone have any suggestions where to start? BTW, earlier today I assumed it just wasn't working (because I couldn't see the faint LEAN indicator dashes) so I just ignored it and proceeded to tune my Profec-B to 11psi max. boost.

I've gone through the full 1st to 2nd gear powerband and most of 3rd with no hesitations, no strange noises and a solid pull to redline... Hmmm... Why would it be running lean (if at all)?

BTW, I've also posted this in the Rotary Performance section as well. :)

you could start by buying a wideband... you're probably wasting a lot of time. maybe the cheapo guage just crapped out?

Sounds like it came disconnected to me.

Hmm... I dunno. Just considering the fact that it worked just fine a week ago and the only variable I can think of as far as it 'crapping out' or getting a bad signal is the removal and reinstallment of the O2 sensor and the "wiggling" of the crappy wiring setup...

It's interesting though, IIRC when an Autometer narrow-band A/F gauge is seeing power but not seeing a true O2 sensor signal, they read a solid and unwavering fully RICH. It doesn't move from the last "bar" of RICH if there's no O2 sensor signal... Can anyone back me up on this?

But mine is just slightly fluctuating around the last two bars of LEAN on the A/F gauge and it's just *barely* visible... I really don't know.

I guess the question is double-sided: If you think the A/F gauge is reading incorrectly, then why? What would've caused this, knowing what I've modified and considering that it worked just a week ago?

OR, if you think the car is literally running lean, what could make it run significantly leaner while still allowing the driveability that I've described?

Consider this: I used to have a significant crack in my TID that caused poor vac. pressure, a worse idle that read LEAN on the A/F gauge, and it had slight hiccups in the powerband. This was a TRUE lean condition and I was able to see it on my narrow-band gauge.

But in this present situation I have found NO leaks after significant "carb-cleaner" spraying and being able to see all of the vac. lines because of the visible simplicity of the removed emissions...

Whatever, I'm obviously in need of guidance. ;)

Check the wiring!

I will... I just kinda want to "drive" it around tonight without blowing it up. :eek:

13psi... :yum:

So check the wiring, tonight, before you drive it around and blow it up! ;)

Hmm... Excellent thought process. I like the way you think. :suspect:

hey erik: newsflash!!!!!!


narrowband widebands are junk.

:rofl: I know, I hate those narrowband widebands.

Godamn losers. :D

You might have a ground problem.
Try running another wire from the gauge ground to the O2 sensor housing.
Easiest way is to run a crimp spade and use a hose clamp to keep it secured.


-Ted

Erik's going to blow his sixth one... I can see it now. You're a boost addict, Erik. I agree, get a wideband. It's on my list to replace this Auto Meter "thing".

josh, this is God speaking.

U are going to run a 10.8@68mph in the 1/8th mile.

thank you my son.

pull the narrowband out and list it up on ebay, it is a useless gauge. i have been in cars with autometer gauges reading damn near full rich which popped under boost, it is nowhere near an accurate gauge for tuning(no we weren't using it for tuning, i was checking fuel pressure at the time)

Jacob,

This will be my first time out of the chute this year... this will be a baseline run for me in this car. However, considering I ran 11's in the N/A, I think we'll shoot for 9's and somewhere closer to 80 mph.

Josh

F**K... The turbo I bought has lost it's oil-seals... :rant: F&$*KIN' GARBAGE $100 TURBO!!!!

I'm pissed.

what kind of oil pressure ar you running and did you modify the crankcase ventilation system and wha kind of boost are you running?

Oil pressure appears to be normal, around 25-30psi at idle and 70?PSI at WOT etc.

The crankcase system can breath via the little 'tube' on the oil-filler neck. I have been running anywhere from 8-11psi.

Did you pull the turbo again?

Swapping turbo's right now. :)

I'm actually going to clean up my "old" turbo with a wire-wheel before installing it though, so it'll be *later* before I can post up the results.

I guess all I really care about is that the smoking stops... I would not want this to be a freak 'rotor oil-seal' thing (which it's 99% definitely not). But we'll see.

Old turbo is back on and there's no oil-smoke and suprisingly, it feels good and boosts hard. There's more to the story than this, but it'd take too long to explain (regarding the compressor hitting the housing).

With a narrowband, there is no such thing as "very". The light is either on, or off, there is no in between. It's the definition of narrowband, that you can't measure it with any device readily available to the public. You are either Rich, or Lean.

Hmm... From my experience, it's decent for telling me what's going on. You can debate all you want, but honestly? When the engine hiccups, the gauge goes red (lean), when I roll into the throttle, the gauge goes from the stoich position and makes it's way into the rich. At WOT it goes rich. At idle it's a (wavering) stoich. It's not just "red and green", you can actually watch and *feel* the changes that the gauge reads.

Actually, not true.

There is a very narrow voltage range which the sensor is very linear.
Outside of that range, it's basically binary.
Please stop making false comments unless you can back them up.


-Ted