Hey y'all!
I have a 1990 volvo 740 gl. It has the redblock B230F with the Regina fuel system. It's throwing a 3-1-1 code. It'll crank and fire no problem, and run if I keep my foot on the gas. But it just will not sit and idle. I had it running a few weeks ago, and drove it to work and church a few times, and it ran fine, but then it just started not wanting to idle. Any ideas will be greatly appreciated! Thanks

things I've replaced so far on this car:
fuel injectors
Fuel filter
Battery
Amm
flushed out fuel tank
Oil
Spark plugs

 

How about the Idle Control Valve, under the intake manifold? May need a cleaning.

 

First check the connectors to the iac. They are directly under the throttle body area whick leaks residues of oil! and often can deteriorate, break or loose good connection.

If you clean it use a good carb cleaner but dont go crazy.
Before you check out these things disconnect negative battery.
If it is indeed your iac needing replacing. I have over 2 dozen all regina iscs available.
Goldenblock

 

So I cleaned the iac like you said, started it and it sat and idled perfectly for about 5 minutes until I touched the gas and it died. I then tried starting it a few more times and it would not idle. Then I cleaned it again, put it back together, and it still won't idle. Do I just need to replace it? Is there anything else it might be? Would a faulty iac throw a 3-1-1 code? Thanks for the response.

 

OK - you don't have to have a working idle motor/control valve/iac - whatever you want to call it.

The base idle speed is controlled by ------- The throttle plate. The throttle plate when warm allows enough air into the engine for it to -------idle.

The iac/idle motor/control valve - allows more idle air when needed. Engine is cold, needs more air, ac is on, needs more air, load on power steering, needs more air.

And stop randomly replacing stuff without doing the basics first.

Your first step would be to remove and clean the throttle plate/housing. Then with a warm engine set the basic idle - in other words - set the idle with the throttle plate to 750 rpms, making sure the throttle switch is adjusted so it clicks when you barely open the plate. Yes at some point you will need to verify the idle motor is not stuck, and is actually working.

Then if you have further running problems - address those

 

On my 89 the green book setting of the base idle is to remove and plug the IAC hose. Set the throttle plate using the screw on the throttle body to 500 rpm. The car should idle provide the throttle plate is clean and not gummed up. Then hook up the IAC hose and the idle should go up to around 750 rpm. Once again it is assumed the IAC is clean and working. Also check for air leaks from the MAF to the throttle body. All of the plastic should be crack free and sealed. My 2 cents here. At 400 K miles my 89 is dead on.

 

I would clamp one of the hoses off, rather than plug - I imagine those are stiff and would crack now

500 rpms worked if everything else is 100% - but so many idle motors are sluggish, and with other contributing factors - some cars would tend to stall when decelerating sometimes if set to 500 rpms.

What years had the spade terminal you could ground to disable the idle motor?

 

My regina wagon is 35 years old and i never once had to clean the throttle body.
I also never touched the idle screw... You dont need to.
ecu will do that automatically. Recheck all vacum hoses if no go replace your Iac
the air temps on these cars dont go bads mafs do!!!

Ignore Hoonks advice and change that iac
Goldenblock!!!

 

Or ignore goldenblocks advice and clean that dirty throttle housing first! That's free! That was part of every major service we did on those engines - because it needed to be done. The way the PCV system dumps some of the fumes back into the intake causes carbon to build up on the throttle plate, reducing the amount of idle air passed.

 

When set at 500rpm at base idle after you plug the IAC hose back into it's normal position the idle should raise to 750 rpm and be steady. The ECU adjusts this.

 

Yes, that's the way is supposed to work.

 

You listen to Goldenblock! He has a Volvo with over 2 million miles with TWO, TWO! fuel pumps, the only one in existence, (that's like having a two headed horse) plus he has a vast idle valve collection, so he really knows what's going on!