Speedtoys

87 S4, everything from the 02 sensor forward is <24mo old, O2 itself, Bosch, 6mo old.

Cat is as far as I know, original.

Greg Brown did the to end refresh, thats the "old" hardware, at 2yrs.

https://www.flickr.com/photos/288046.../shares/gY040L

High in HC, rest looks..ok.

Thinking cats, I have at least 2-3 sets in storage.

Am gathering Sharktuner and WBO2 logs starting today for the next 3-4 days of driving for peer review.

dr bob

you know the drill --

High hc is fuel that's passed through without burning. look for ignition issues first. Then look at mixture problem (lean) that's causing a misfire. Low exhaust port temp may steer you.

Speedtoys

"Then look at mixture problem (lean)"

The WB is reading 14.7-15.3-4

14.7 is not 'middle' of the swing in cruise AFRs.

V2Rocket

definitely lean, the O2% should be 0.0-0.3 or so and the NOX is near limits too.

Mrmerlin

I would swap in another MAF

dr bob

The WB02 reads from the mixed exhaust from all the cylinders, so the CO reading is the sum of CO over the total of all 8 cylinders' worth of gas flow. A "local" issue, maybe a sticky, partialy clogged or otherwise weak injector can easily go lean enough to allow unburned HC to pass through to the exhaust. It can be a leaky o-ring on one or two injectors. It doesn't take much. How well/smooth does it idle?

Read back through the Kibort thread on his miss-at-idle for all the hints/clues. Stan's recommendation for another MAF may help, but if the WB02 readings are as you say, there's not much another MAF can do. The testing is steady-state so slow MAF and oxy sensor response is not really a factor.

My nickle is on a small vacuum leak. If the injectors are new in the last couple years, they are less suspect. There's always a look with a 'scope at the ignition patterns, looking for one that's different then figuring out why. 'Scopes are kind of old-school, but they get the job done. Plenty useful diagnosing sensors like the Hall and the CPS, and even the knock sensors if you want to get creative. One of the USB plug-ins with the soft spectrum analyzer would be a treat for the knock sensors.

Speedtoys

Ya, this MAF was new 4yrs ago from Roger.

My logged WB #s dont match what the display of the WB says...they're quite a bit richer.

Im...kind of questioning the WB some at this point. But I need to study the injectors more...make sure I have dead times right, size...just check things over, because I -can-. *cough*

worf928

This-^

If you've got one cylinder - or one side - getting false air, the LH will richen everything and you'll get too much unburned fuel out of the 'working' cylinders while the max fuel trim from the LH's 02 loop won't get the lean cylinders back to normal.

Based on the report, you're running both rich (excess HC) and lean (NOx is byproduct of lean.)

It could be cats. But, the stock cats will work for a long time unless they've run rich for a lot of their life. If you've got cheap 'racing' cats.... oh. Kalifornia. You don't have racing cats...

Speedtoys

Well..lets just understand theres no such thing as racing cats...nobodys every turned an S4 stock/racing cat Dyno sheet...

Theyre just well marketed units that last 2yrs, then you need more.

There was a 5mp period it did run rich, until I got to the bottom of that.

And the last vac leak was resolved with an HVAC system rebuild a month ago. The rest under the hood..is new.

I may have to wait until October to get on this.

Mrmerlin

another thought,
the injectors that are supplied from lets say Witchunter might have a lower O ring thats a shade thinner than it should be,
put this into a freshly powder coated intake and it can be a recipe for a vacuum leak.

You might have to pull the injectors and see if any of them come out easily,
if so then replacing the lower O rings with the correct Bosch S4 O rings could be a cure.
I have had this happen a few times on intake refreshed cars.

NOTE the inner ID of the O ring could also be too big so the O ring wont seal on the injector and this could be the pathway.

I use DC 111 on the O rings to increase the sealing properties of the O ring,
BUT if the O ring is loose fit on the injector best to replace it

Speedtoys

the lower rings are correct...well, as correct as Greg Brown working on it can be.

Her performed the refresh 2yrs ago.

worf928

Exactly. And they're not CARB'd. And thus, you are unlikely to have them.

The tiny amount of false air through the HVAC system to the intake plenum will have an effect that is 'in the noise' relative to your emissions report. And then, because it would effect all cylinders, only if the 02 loop is at or near it's max trim.

GregBBRD

I don't think you can have .12 CO and have an intake leak.....

Working O2 sensor, with working MAF, and a working factory cat will generally register .02 CO.

Apparently the engine is Sharktuned. Make sure that you have the stock O2 sensor turned on....many people forget to do this, after they are done tuning.

If the car has been Sharktuned and you like the way it runs, save the LH and the EZK. Then load in a stock S4 program from Sharktuner. Drive it around, with the stock O2 sensor hooked up and active to the LH (don't shut off the O2 sensor) and see what the correction factor is. If it is in the negative numbers, swap in a good rebuilt MAF....from John Speake.

worf928

I've seen something similar. Some other shop did the injector service on an early '87 with the rubber fuel rail stand-offs. They replaced the stand-offs with ones that were about 2mm too thick. Thus not all of the injectors would seal. A smoke test of the intake made it very clear that one side of the engine was sucking air past the lower o-rings and the other wasn't. High NOx and HC cured with the proper 928 stand-offs. I was on the other end of the phone for this for months, and thus couldn't visually inspect anything. Once the owner got the smoke test done, he brought it to me for the final diagnosis and repair.

Speedtoys

Im at OEM tune for smog, has been in prep for this for the last month, keyed to 24# 0280150706 bosch injectors.

The corrections ATM, are both +9%.

I may do a custom injector size, these really, according to Bosch, flow 23lbs, so I can adjust that.