logray

The SAI should start shortly after you start the engine whether you want it to or not. It is also normal for it to start at other times (here is a link to a very technical explanation). It is basically just a pump that dumps oxygen into the exhaust on a cold start (into the top of the block into a channel through the head and out the exhaust manifold). Yes, the secondary air system and DME also operates various check valves around the car including SAI check valve and resonance flap to name a few.

At least on the 1999 car, there are potentials for leaks within the SAI system as well, a couple of the air tubes enter the intake plenums and if they are disconnected or cracked there will be exposed holes to the intake, albeit very small.

Yours probably looks a little different than the one on my 1999 car, it has a 993's design. In later cars they combined the two check valves into one, among some other changes.



Check out this nightmare, my lower check valve was chocked with carbon, and several of the tubes were broken in half. I finally got the spiderweb back together (the big hose in the upper right goes into the pump).

seanmcr6

TRA/FRA?

Timing advance?

I've inspected the oil filler tube before...it's good.

My MAP is rated in inHg

My MAF is g/s

logray

TRA/FRA = fuel adaption. There are values to monitor in Durametric.

" TRA - Time Relative Adaptation; a fuel injection adaptation method used to compensate for engine/
sensor changes at idle, which are short term & small affecting the AFR, e.g. intake air leaks,
and which generally varies equally with +/- values under normal conditions "

" FRA - Fractional Relative Adaptation; a fuel injection adaptation method used to compensate
for engine/sensor changes under load which affect the AFR, e.g. MAFS output error,
with some ECMs retaining the old FRA values with battery removal & not updating until
closed loop operation returns via the O2 sensors "

The oil filler tube might have a hairline crack only detectable with a smoke machine. Also, (not advised) spraying carb cleaner in the intake area to see if the engine stumbles, indicating the cleaner is getting into an area with a leak.

OK math time.

DME setpoint of air mass with engine idling.

170 Hg = 17 Kg. +/- 25 Hg = 2.5 Kg

What is the interval/period for Hg in Durametric, is it per hour, minute, second?

logray

For a C4S 3.6 liter engine with no loads switched on (no AC), Engine temperature greater than 90 °C, and Ambient temperature 20 °C the values should be:

Idle - 16-20 Mass air flow ML in kg/h
No load at 3000 RPM - 60-80 Mass air flow ML in kg/h

I would want to see what those values are with a warm engine, if yours are different then that might point to an intake or vacuum leak or bad MAF, or problem in fuel delivery system.

seanmcr6

ok, I will check those values with the durametric tomorrow morning.

I will check the MAF at lunch with my iphone...

sean

seanmcr6

K...here we go...

Here is what Dash Command is reporting (reading from ODBII)

at idle:


Doing the math, this works out to 14.4 Kg/H

At 3200 rpm:


At 3200, I'm at 50 Kg/H

Also ran the GoLink reader, and it pulled the following info from the O2 sensors. Are they supposed to cycle like that?

Bank 1 Sensor 1


Bank 1 Sensor 2


Bank 2 Sensor 2


I missed Bank 2 sensor 1...and I just took screen caps at random times...

Thoughts?
sean

Ahsai

All your numbers look fine. Note that our cars don't have a MAP sensor so any MAP sensor readings are only derived from the MAF. We do need to see the TRA and FRA for a complete picture. I also vote for small vacuum leak somewhere. Is your CEL on currently? If so, what are the codes? I wonder what that "1" under the engine icon on the Dash Command is...

seanmcr6

Did even notice that 1....however, I have no CEL, no codes. Checked for codes with the Durametric last night, with the Dash command and the Go Link today. No codes at all.

Ahsai

[QUOTE=seanmcr6;8691651]Did even notice that 1....however, I have no CEL, no codes. Checked for codes with the Durametric last night, with
I see. Do you think your engine starts to stumbles the same instance the air pump is turned ON? If so, that strongly points to (maybe small) vacuum leak there since your said the engine stumbles only when cold so only when the air pump is on.

seanmcr6

LOL...so I just found out there is 2 pages under the engine section...that's what the 1 was.

Fuel trims....

I don't know what ST and LT are....but LT barely ever moved. ST moved up when revving the engine. At idle...it would bounce around in the negative end of the scale. It is supposed to move around like that?



While revving....

Ahsai

LOL... that makes sense. Yes, the short term fuel trim moves quickly to adapt to the A/F ratio in real-time. +/-10% is considered normal. Long term fuel trim moves very slowly and also +/-10% is normal (0 is ideal)

These are bank 1 numbers and they look good to me. +3.1% long term fuel trim is not significant to conclude there's a vacuum leak though. Besides, if the leak only happens when SAI is on, that would not show up on these fuel trims at all. Any way to get the Bank 2 numbers?

seanmcr6

Yes, with my durametric....so tomorrow morning, while the engine is cold, I'll run it....

logray

Also it would be nice to see the "engine warmed up over 90C" air flow numbers at idle and 3000RPM in the Kg/Hr format... perhaps Durametric will log in that format.

Not that I don't think your iphone tool is cool though.

logray

These numbers are a little low, but not too far out of spec. Like I said previously would be interesting what you see once the car is warmed up to 90C and all loads incl. A/C switched off.

seanmcr6

God damn this startup procedure with the durametric is a pain in the ****....

So I finally get it working (latest version) and start the car. It's very rough this morning. In fact, the car is shaking side to side when it stumbles. then it revs up and smoothes out. When it goes closed, all is right with the world. Same, same.

Unfortunately, I didn't "record" any of the data, I just watched it.

The only think I could find was FRAU..adaption range 2 lower Bank 1 and 2

I did that plus an O2 sensor and a couple other things. I really wish I had recorded them

And, the interesting parts (maybe?) was that the Adaption Rage 2 lower (FRAU) Bank 2 was noticeably lower then the rest. All the other held values of 1 or .98....this one was .68. So I had 5 coloured lines all stuck together around the 1 mark...and this lone green line down at .68 Once the system went closed...the other numbers all shifted a little. Fanned out as it were...this bank stayed at .68

Then, just to add to the whole conundrum...I always check for codes every time I connect to the DME. I haven't had a SINGLE code in all this time. Even when the water pump was blowing up. Today...just before unplugging, I check codes....big RED error code.

P1341
Fault Code 900 - Inlet Camshaft Bank 1

Sigh...so this might be a bigger problem than just a faulty sensor?!

That would certainly explain the shakiness at startup if one side of the engine wasn't being powered the same as the other...

Is it possible that the AOS could leak into the right side intake....just a little bit? I get NO smoke on start up or at any time.

I'm grasping at straws....