CIS sensor plate sticks when afr correct

jtamborra · jtamborra's Garage

I have an issue with my newly rebuilt 3.3 turbo. I took it to good porsche mechanic to have AFR, idle air and timing adjusted, as I just couldn't find the right combination myself. The car runs better than ever now, idle is perfect, pulls hard to redline, etc...BUT, if it sits for any more than a day, I have to push the CIS sensor plate with my finger (I actually use the AFR adjustment tool) and make it "squeak" the injectors before it will start and slowly lumber to life. It seems to crackle a LOT more than ever before, on throttle-off rolling. Kinda TOO much, even though I like it. I'm guessing this is a lean condition, and the easy answer is to richen it up some, but HOW much adjustment is needed to make this SLIGHT change? Is a half turn too much?? What about a whole turn?? (Clockwise is richer, right??) I don't have AFR meter, and I know it's darn close to perfect now, so a slight adjustment is all I want.

Is there some maintenance condition that would make the sensor plate sticky in this particular setup? I didn't disassemble any CIS components when I rebuilt motor, but I did clean out the housing and a little silicone spray on the plunger pivot mechs. Seemed pretty smoothly operating when I had it out and drained of fuel, like a nice balance it pivoted..

jsveb · jsveb's Garage

Could be the cold control pressure in the WUR that is too high.

oilonly · 03-04-2013, 04:14 AM

Quote:

Is a half turn too much??

I would go with a 1/8th turn clockwise to richen a little.

mooney265 · mooney265's Garage

The "squeak" you referred to is normal... it's really just the sound of the fuel under pressure rushing through a tiny orifice.

If you had an adjustable WUR, i'd tell you to lower you cold cp a bit. but, it appears you don't, so the 1/8 turn to the right [cw] may help a bit...

jtamborra · jtamborra's Garage

OK, 1/8th turn CW it is, thanks for the ideas. I do tend to think the control pressure is a little too high, as the sensor plate floated like butter when I had engine disassembled, but now when system is pressurized seems really stiff to deflect.
Is the CP non-adjustable w/ stock WUR? Or is this the fabled "tap the pin" method I'm needing to learn/understand? I'll start w/ the 1/8th turn richer, but I really like the PULL I'm getting with this current leaner setting. Is this a common tipping point?? Hard to start but runs sweet, OR easy to start w/ some performance compromise?

thx pelican-ers!

mooney265 · mooney265's Garage

Quote:

Originally Posted by jtamborra

OK, 1/8th turn CW it is, thanks for the ideas. I do tend to think the control pressure is a little too high, as the sensor plate floated like butter when I had engine disassembled, but now when system is pressurized seems really stiff to deflect.
Is the CP non-adjustable w/ stock WUR? Or is this the fabled "tap the pin" method I'm needing to learn/understand? I'll start w/ the 1/8th turn richer, but I really like the PULL I'm getting with this current leaner setting. Is this a common tipping point?? Hard to start but runs sweet, OR easy to start w/ some performance compromise?

thx pelican-ers!

The sensor plate would be easy to push without the Fuel Pressure "pushing back" - - so, what you've said is happening should be happening.

You need to invest in a Adj-WUR and some CIS gauges. Would be a big leap forward in knowing what's going on with your "pressures." In the meantime: while engine off [for your purposes]: the 1/8 turn is done by inserting 3mm allen wrench, pushing down about 1/2 inch, then turning. **** You should feel resistance! If you turn and no resistance, you haven't pushed the adjustment screw in enough...

T77911S · 03-04-2013, 09:06 AM

try some injection cleaner. i run a bottle to a half tank. run the RPM's up while driving.

wjfk32 · 03-04-2013, 10:46 AM

CHK THIS OUT..

930 popping on decell

oilonly · 03-04-2013, 11:12 AM

Quote:

Is this a common tipping point?? Hard to start but runs sweet, OR easy to start w/ some performance compromise?

It can be a multitude of things but for me the only time I had a cold start problem is when I gutted my emissions crap and did not know I had to switch my vacum lines around also. My personal opinion is you need an on board AFR meter for these cars. JMHO

j930 · j930's Garage

what did you have to switch around on vacuum lines? any diagrams

oilonly · 03-04-2013, 03:50 PM

Quote:

Originally Posted by j930

what did you have to switch around on vacuum lines? any diagrams

Different on 76 to 79 vehicles but for 86 to 89 here is the chart.

'78 SC Turbo Conversion Begins

Early and late throttle body comparison.

Early and Late throttle body comparison

To sum it up the upper outer facing port on the distributor goes to (V) and the lower inner facing port on the distributor goes (I). (II) is plugged. I have the lower inner facing port on the distributor going to the therm switch in back of the engine and then to (I) but some people skip that as the chart shows. Got this tip from Helio.