308 328 WUR warm up regulator

Larry,

a steady small miss or only under load?

Although mostly used on Carbed Cars to set mixture & tune the carbs a Gunsons Color Tune can be used on FI engines to track down running anomolies just as well. One can use the Color Tune to find bad plug wires or dirty/faulty injectors by comparing the color patterns cylnder to cylnder.

Regards, JRV

A steady miss at light load from 2.5-4k rpm,
any increase throttle or uphill, it goes away, excellent wide open.
New plugs, wires, injectors, O2 sensor.
I check all exhausts @ manifold plugs:
exhaust readings: (w/02 sensor unplugged)
cyl - C0 - CO2 - O2 - HC
1 - .46 - 10.1 - 6.0 - 98 ppm
2 - .95 -- 9.2 - 6.1 - 99
3 - 1.50 - 9.6 - 4.7 - 157
4 - .57 - 10.6 - 3.7 - 105
5 - .27 -- 8.6 - 6.6 - 99
6 - .18 -- 6.6 - 8.1 - 292
7 - .34 -- 8.2 - 6.5 - 112
8 - .36 -- 7.1 - 7.5 - 110

It passed California smog test, so it's not anything major. I think just a tad lean.
If I adjust 3mm allen screw, won't the O2/frequency valve just compensate for it?

Larry

Larry,

unbelievable and fantastic you pulled 8 port numbers...BRAVO!!!!

#6 is WAY Lean...I would definately want to correct those numbers.

#3 Way rich

#5 too lean

looking at the numbers gives several possibilities......bad/dirty injectors (spray patterns inconsistent or off angle).....intake aire leak.......unbalanced FD ports. This ALL assumes vale lash and valve sealing condition is consistant across the heads, both banks.

Are the injectors new?

Yes, new injectors.
I think I get it now, the seperate cylinders can be rich or lean,
the O2 sensor reads it overall and makes adjustments from there.
So if #6 is lean and the 02 sensor senses rich overall,
it further leans out all cylinders....
After I confirm valve clearances and compression,
I will adjust at distributor.
Is it common to see this variance between cylinders ? (it is a 20yr old car!)
Thanks teacher......Larry

A cylindr leakage test will give a good overview of each cylinder condition. A small amount of pitting on valve seats can affect the cyl/cyl balance but I would also double check the basics, fuel pressure, injectors and their sealing, it seems like variation in the air/fuel distribution is slight but the O2 sensor may be compensating for the rich cylinder a little which leans the lean even more and thus increases the HC, then the O2 sensor will swing way over again.

>>the seperate cylinders can be rich or lean,<<

correct...not supposed to be, but some variance can almost be expected.

>>the O2 sensor reads it overall and makes adjustments from there. <<

again correct....however, specifically, the O2 sensor only tells the computer to tell the frequency valve to raise or lower overall fuel pressure...which would have a positive or negative effect on individual cylnders already to high or to low.

>>So if #6 is lean and the 02 sensor senses rich overall,
it further leans out all cylinders.... <<

correct...by raising FP slightly (via frequency valve pulse width)adding resistance to the air flow meter plate.

I would look first for an airleak on #6...very low CO &amp; High HC is often an intake leak causing a "lean miss"...

Cylinder #3 very well could be a FD port adjustment issue as it's very rich (quite a bit out of spec on the rich side).

Cylinder #2 has absolutely the best numbers of all the cylinders and if you proceed to a thourough port adjustment procedure you should shoot for those numbers overall. I will mention that testing &amp; tuning should be done with the O2 sensor disconnected to insure you are reading the real raw numbers the systems are operating at.

Regards, JRV

JRV what are the ideal #'s? 1.0 CO and ??? HC. Thanks.

Rich,

on a well running cyliner or engine the HC #'s should track very close to the CO #.

for example...1% CO &amp; 100PPM HC (or less)is a very good reading. 1% CO 150ppm HC is on the poor side of combustion efficiency. HC readings over about 180-200 are not very good on a FI Ferrari engine, over 250 and a definate problem exists.