So about 4 or 5 months ago I got an 81' 240 to replace my totaled 89' 740. I really like it but it has a problem I can't figure out. When I start it cold, it idles in park at about 1500-1900 rpm, and in drive at about 1000-1100 rpm. If I had to get more detailed I'd say that it starts out idling cold at about 1900 rpm, and then after a bit drops to 1500 rpm (presumably after the engine warms up). I used to have an 89' Chevy blazer that idled high, and it turned out to be a dirty Idle Air Control Valve. Anyone know if my Volvo might have something similar? I know that this car came with two different types of fuel injection systems, but I don't know which mine has. I'm probably gonna start tearing into the intake this weekend, just hoping to get a little info on which direction to go in. Any knowledge at all will be helpful!

 

81 is probably KE-Jetronics, continuous injection (CIS-E). works off fuel pressure, the injectors spray continuously. the air goes past an air flow meter which is a brass plate in a venturi, with a rocker arm, that presses on a pin into the fuel distributor, which has a whole bunch of little springs and diaphrams in it, and it works without any electricity other than the fuel pumps.

there is a 'control pressure regulator' which IS electrical, this is driven by a control unit which monitors the O2 sensor.

there is an idle air controller (IAC), its under the intake manifold, and has hoses to both sides of the throttle body, the idle circuit modulates this to set the idle.

with the engine fully warmed up, in neutral, it should idle about 500 rpm with the IAC unplugged. when the idle control circuit is working, it should idle around 700-750 rpm, regardless of being in park or drive, ac running or not. cold idle is more like 1000 or even 1200 if really cold, when it warms up this should drop to 700-ish.

K-Jet.org has a bunch of stuff on k-jet volvos. i'm much more familiar with LH2.2, 2.4 systems.

 

Thanks, I'll try unplugging the IAC, see if that has an effect.

 

Curious about any updates on your idle problem, lukem. I'm going through some similar issues with an 86 245 dl.

 

Totally different fuel injection systems between '81 and '88.

 

My 86 has LH2.2

 

and a 1981 has KE-Jetronics, aka CIS-E or 'mechanical' injection.

LH injection started in 82.

 

a day late again and a dollar short

 

I found a manual online that allowed me to identify my engine as a B21 F-5, which I think is the other type of injection, the manual said Bosch i think. Anyway, the intake is set up as follows. Under the intake manifold there is an almost spherical rubber bit. under that is a metal piece that looks important. Attached, but not leading into, the rubber piece is some sort of electronic sensor or valve. It has two hoses, one that attaches to the manifold, and the other which attaches to some sort of metal housing next to the manifold. The Sensor/valve has an electronic plug attached to it. if i unplug it, the cold idle in park is around 1000 to 1100 rpm, and in drive is about 900 rpm. but if i try and rev the engine with it unplugged it doesn't rev cleanly. Is this the IAC, and if i replace it will it fix my problem?

 

Bosch made both the KE and LH injection, so saying its Bosch really doesn't say much.

the IAC has two rubber hoses, one to each side of the throttle body. normally the IAC is closed so no air goes through it, when the idle controller pulses it, it opens and allows extra air through. with it closed off, a warmed up engine should idle at about 500rpm in neutral with no accessories switched on. if its idling higher, either the throttle has been badly misadjusted by someone who didn' t know what they are doing, or either the throttle or the IAC is gummed up and not closing.

 

Can you take a picture and upload that? It is obvious when seen which system you have and we could identify the IAC valve for you. From your description it sounds like you have KE-Jetronic (mechanical) fuel injection. Unplugging the IAC should not affect the revving of the engine.

 

this is a K-Jet engine





there's a couple different idle valves depending on federal vs california and other stuff, so don't let the marked valve on the first one fool you.

per this page, B21 Motor Guide | K-Jet.org (scrolling down to 1981 B21f-5), he details some differences in the various idle circuits.

 

Thanks you guys. I will go take some pics today, will post them this afternoon.

 

Here some pics. I don't see what you labeled as the IAC on my engine, so I'm guessing I have a different valve. The third picture is of the connection I unplugged. When I unplug it the idle drops.

 

find the 2 hoses coming off that device, they should go to either side of the throttle under the manifold

make sure the throttle is completely closing, and that those hoses to the IAC are in good shape and firmly connected. any cracks will leak air and boost your idle speed.

 

Thanks Pierce, I'll try that tomorrow, let everyone know how it goes afterward.

 

oh, the thing you unplugged, I believe thats the 'control pressure modulator', used by the lambda circuit (o2 sensor) to fine tune fuel pressure.

K-Jet is fuel pressure driven. the fuel 'distributor' is really a variable pressure valve. more air through the air flow meter turns up the fuel pressure, more pressure causes the injectors to spray more fuel to balance the more air. the control pressur emodulator acts as a fine tuner on this to maintain proper stoichastic mixture as detected by the o2 sensor.

 

I got a chance today and tried unplugging the IAC valve. The idle didn't change with it unplugged, which makes me think the IAC is stuck open, or that one of the hoses going to it is broken. Will investigate tommorow.

 

You don't have an idle air control valve, you have an auxiliary air regulator. It is the silver thing sticking up between the intake and the valve/cam cover. If there is not an issue with your accelerator cable or your throttle not closing completely or the throttle switch adjustment, then this is likely the problem. Disconnect the hoses and electrical connector from the air regulator then unscrew it and remove it from the car. Take a flashlight or hold it up to a light bulb and look inside the port. If it is cold, you should be able to see through it. Attach it to a 12Vdc source (I use an a/c adapter with the dc plug cut off and just use the wires from that) at the electrical connection for five minutes and see that the port is now closed. If not, check the resistance. It should be about 30 ohms.

Only California cars have the constant idle speed system with an IAC. Federal cars use the air regulator and it only operates during the first few minutes of operation starting at open, then it closes..

 

So I Checked out the IAC (Or the auxillary air reg.?), and it seemed fine. Behind the throttle pulley I found on the throttle body a little plastic **** that seemed to be an idle adjustment. Using this, I was able to get my idle down into the normal range. It runs smooth and seems to accelerate well. I'm hoping this will make my MPG a little better (last fill up I was at 17-18 mpg highway), but we'll see. Can anyone think of a reason that this isn't an appropriate way to lower the idle?