I have a 78 242 B21F that starts but idles very rough until it begins to warm up. I did a "freezer test" on the aux air valve which when cold is only slighty open--a tiny crescent. I tried spraying cleaner and lubricant in it and physically opening it and allowing it to close with a small screwdriver. My question is: how far open should the gate be when the valve is cold? Should it open up at least halfway? All the way? I suspect my rough idle problem is at least partly because the cold start injector is working and the necessary extra air is not being provided on cold start. Comments please.

Thanks lucid and Nickvjr! I really appreciate the help. I adjusted the aav and that seems to help some. Next I will r and r the cpr. This may just be the culprit--especially since this car sat for some months until I broke it out and repainted it...it's now a beautiful 78GT. It was my daily driver for several years and it used to run great...which I'm sure it will again. Can't wait to really put the power to the new ipd sways. Again thanks for your time and expertise.

Sorry for the double post but one last thing, your cold start injector only works while the starter motor is engaged when you have a cold engine. Once the engine catched and runs/stumbles on its own the cold start injector stops. Another time your cold start injector works is during a WARM start in you have a IMPULSE RELAY installed. This relay allow tiny pulses to the cold start injector after a warm start to help assist the idle till the engine gets back up to normal operation temperature. Just thought this info will also help you understand the CI System function thus helping you solve your problem. Good Luck!

Sincerely,
--
Nickvjr

1979 264GL B27F 121K

Features Added:

Central Locking System, 25mm IPD Front Sway Bar, 81+ Dash W/ Oil & Ambient Temp Gauges In C, Oil Pressure, Volts

Next Project:

Add Cruise & BW55 Swap To A M46

The Volvo Factory Manual I have on the Construction & Function of the CI System states that the AAV fully opens at -30C/-22F . The book also states that the valve is fully opened at +70C/158F or after the equivalent of running the engine for five minutes at an ambient temperature of 20C/68F . So basically unless it is colder than cold then all you would see is that cresent shape opening. As far as your idle problem it seems that the AAV is not your problem but that you may have extra air leaking in between the air flow sensor and the intake valves. Any leaks in between cheats the air flow sensor thus not allowing it to raise enough to provide a richer mixture when it really needs it.

Another possible cause could be a gummed up Control Pressure Regulator. If the CPR is gummed up then the plunger on the fuel distributor is being pressed down all the time. The purpose for the CPR is to relieve the pressure on the plunger when cold by means of a bi-metallic piece of metal pushing down on a spring. This piece of metal (when cold) pushes down on that spring allowing more fuel to return back to the tank thus lowering the control pressure on top of the plunger making it easy for the plunger to move up with less air flow causing a richer mixture. As the car warms up a small heating device wrapped aroung the bi-metallic spring warms it up causing it to bend after about 5 minutes. When the metal bends the spring force ends up winning and thus restricts the flow of fuel back to the tank causing a greater amount of control pressure on top of the plunger making it harder to richen the mixture. My 1979 264GL has a gummed up CPR and I have the exact same problems and my CPR is currently soaking in a bath of TECHRON till tomorrow. PHEW!!!

The following links will take you to previous posts that teach you how to clean the CPR.

Link #1
Link #2

I hope this info helps and post back any results or question you may have. By the way the book where I got all the knowledge from is for sale on Ebay. Good Luck!

Sincerely,
--
Nickvjr

1979 264GL B27F 121K

Features Added:

Central Locking System, 25mm IPD Front Sway Bar, 81+ Dash W/ Oil & Ambient Temp Gauges In C, Oil Pressure, Volts

Next Project:

Add Cruise & BW55 Swap To A M46

The Volvo Factory Manual I have on the Construction & Function of the CI System states that the AAV fully opens at -30C/-22F . The book also states that the valve is fully opened at +70C/158F or after the equivalent of running the engine for five minutes at an ambient temperature of 20C/68F . So basically unless it is colder than cold then all you would see is that cresent shape opening. As far as your idle problem it seems that the AAV is not your problem but that you may have extra air leaking in between the air flow sensor and the intake valves. Any leaks in between cheats the air flow sensor thus not allowing it to raise enough to provide a richer mixture when it really needs it.

Another possible cause could be a gummed up Control Pressure Regulator. If the CPR is gummed up then the plunger on the fuel distributor is being pressed down all the time. The purpose for the CPR is to relieve the pressure on the plunger when cold by means of a bi-metallic piece of metal pushing down on a spring. This piece of metal (when cold) pushes down on that spring allowing more fuel to return back to the tank thus lowering the control pressure on top of the plunger making it easy for the plunger to move up with less air flow causing a richer mixture. As the car warms up a small heating device wrapped aroung the bi-metallic spring warms it up causing it to bend after about 5 minutes. When the metal bends the spring force ends up winning and thus restricts the flow of fuel back to the tank causing a greater amount of control pressure on top of the plunger making it harder to richen the mixture. My 1979 264GL has a gummed up CPR and I have the exact same problems and my CPR is currently soaking in a bath of TECHRON till tomorrow. PHEW!!!

The following links will take you to previous posts that teach you how to clean the CPR.

a href="http://brickboard.com/ARCHIVES/1997DEC/6460.shtml">Link #1
a href="http://www.brickboard.com/ARCHIVES/1998AUG/20008879.shtml">Link #2

I hope this info helps and post back any results or question you may have. By the way the book where I got all the knowledge from is for sale on Ebay. Good Luck!

Sincerely,
--
Nickvjr

1979 264GL B27F 121K

Features Added:

Central Locking System, 25mm IPD Front Sway Bar, 81+ Dash W/ Oil & Ambient Temp Gauges In C, Oil Pressure, Volts

Next Project:

Add Cruise & BW55 Swap To A M46

I can't give an opening dimension, but my memory sees it as a crescent whose max width is about 25% of its height. Maybe a bit wider.

The opening can sometimes be increase by loosening the nut that is "south west" of the opening (looking straight in), and moving it to the "north west" as much as possible, then tightening it.

Hope that helps,

--
Bruce Young,
'93 940-NA (current)
'80 GLE V8 (Sold 5/03)
'83 Turbo 245
'76 244 (lasted only 255,000 miles)
73 142 (98K)
'71 144 (track modified--crusher bound)
New 144 from '67 to '78
Used '62 122 from '63 to '67