Possible MAF Issue-PSI3 Readings
 

In the last day or so I have noticed that there has been a slight lumpiness/maybe a miss every now and then when on partial throttle, not very often, and the revs will sometimes drop off to about 600rpm then back up to the 750 area when coming out of gear(not every time). There are no CELs.
I had a look at the PSI3 on idle and had these figs that may give you some idea:-
IG (which i presume is the same as Ignition Advance IA)= 10-12 degrees.
LA= 12:1-13.5:1
Now I remember it has been said that stoich is 14.7:1 so am wondering how far into the rich I am going with this LA fig?
I did an ECU reset and the figures were pretty much the same.
What sounds like the problem in you guys' experience. I have read up and it sounds like it could be the MAF on its way, do these symptoms sound familiar? Anywhere else you can point me for diagnosis?

All help appreciated guys.

If you got to the AF display on your psi3 it should show you how much air the maff thinks it is seeing, have a look at the g/s reading and see if its altering as you rev it, you can do the same for the rear 02 volt wise and see how it is responding.

Yeah, the PSI monitors AF in grams/sec I think. Is that a reflection of MAF output?

How would I monitor the rear o2 sensor output?

The g/s is a value denoted by the voltage at the MAF measuring airflow. The more air the higher the voltage.

LV is lambda voltage

Ah, is LV on the PSI3 options?

So does LA equate to maf and LV equate to O2 sensor output?

Using the PSi for detailed diagnostics isn't easy...the IA isn't really ignition advance and the readings for the AFR are not stored. If you want to do a detailed diagnostics then it's delta dash or equivalent. Either that or swap the MAF for a working item and see if the situation improves.

Shaun

The idle ignition advance you are seeing is correct. The air/fuel ratio is very rich (should of course be 14.5 - 14.7) You would normally see those figures when on mid boost. As said, check out the airflow reading to see how the MAF is behaving.

JohnD

I have a good maf to sell if you need one, its newage.

Cheers guys, what figs should I be looking at on airflow?

Steve, pm me some details.

Right, I hope these figs are relevant:-

Idle 4.8 g/s
2k 11.5g/s
3k 17.9g/s

All done in neutral.

JohnD

I thought the SECS only displayed the difference between the data stored on the table and the Advance the ECU was running and the same went for Knock correction ?

Or am I dreaming, well it was quite a few years since I sat in my Bug with Bob Rawle LOL

I'll see what my SECS displays later :)

Shaun

[QUOTE=Midlife......;10222226]JohnD

I thought the SECS only displayed the difference between the data stored on the table and the Advance the ECU was running and the same went for Knock correction ?

Or am I dreaming, well it was quite a few years since I sat in my Bug with Bob Rawle LOL

I'll see what my SECS displays later :)

Shaun[/QUOT

The PSi3 shows real time ignition advance and, if you choose to display it, the Knock correction. The KC values you normally see are actually the extra advance put on by the ECU when accelerating.
Typically, cruising with low throttle and mid range revs you should see over 40deg. advance with no KC value. If you accelerate with part throttle the Kc value can be + 8 - 9deg. (The vacuum advance did all that sort of thing back in old days!:sleep:)
The above is how I understand it, anyway:wonder:

JohnD

Are there any more opinions on the figs above, and come to that the PSI3's usefulness as a monitor?