Told u I would be back, 88 740 gle running good now with the exception of wanting to cut off when coming to a stop. Rpms drop to much causing low idle. I have adjusted tps and throttle linkage. When I unplug iacv, there is no change in idle and if I crimp hose going to throttle body from iacv, idle drops. Does this mean iacv is good or bad, also while examining iac, the valve inside turns freely, and the arrow on outside of iacv is pointing towards block, is this correct or should it be towards tb

 

Pretty sure the arrow is air flow...so it should be pointing towards the TB. Have you tried idling it up with the black **** on the TB?

 

Yes, have messed with black adjustment ****. I have it set to about 1k rpm know at idle. I just have to put in neutral upon coming to red lite so it doesn't idle down to far and cut off. Iac appears clean on inside but should the valve just rotate freely in there.

 

OK...if the idle drops when the hose is pinched AND the iac has no reaction when unplugged, one or more of the following has/have happened...1. The iac has become sludged up from years of oily air vapor. It can be removed and cleaned up using a solvent, I prefer using brake fluid. 2. the iac has simply died 3. the iac is receiving no signal because a. the connector plug/wiring has failed 2. that portion of the ecu has died
I had a similar situation occur on my 84 760. See, when the iac fails, the car has an unacceptably high/hunting idle generally. It's useful when the temp is cold and so is engine, similar to high idle on a carb. Because of the high idle, most folks idle it way down using the black ****. This can work sometimes but does not allow for a higher idle when needed and the engine will die. In my case, it ended up being the idle circuit in the ecu had failed although that is rather unusual. For me, the temporary solution was to set the idle where it should be if it could control itself (1500-1800) and then restrict the iac hose w/ locking hose pliars. It worked for all but the coldest of winter days...at which time I would adjust the clamping pressure by a click or two. Not a solution but a quick work around. You can see the pliers behind the power steering.

 

K, thanks swift justice, the valve itself is clean as can be on the inside, however , while in my hand if I rotate the whole unit, I can see and hear valve rotate within leaden me to be leave it's bad. There's 3 pins, which one should power on it at terminal plug and which pins could I apply volts and ground too on valve to see if it actually does any thing

 

In the diagram, 196 is the IAC

 

Thanks again, will diagnose tomorrow and post back.

 

ok, have cleaned iacv, while in hand if i apply 12v to center pen and grnd to outer pins one at a time , valve does move closed/ open as it should. With key on, center pin of harness plug has 12v. should either of the 2 outer pins be grounde now? OR should that only happen when car is running and on cold start, one side be grounded to open valve and then vice versa for other other pin to close valve?? Also upon cleaning TB again (just did a couple days ago) i notice that it is wet as hell inside with oily gas, is that proably clogged flam trap that ive been reading about. The hose from flam trap to the large plastic intake house is just caked full of what looks like yellow puss.

 

Follow up. Have removed and all pcv components,I.e. Hoses,fittings, flame trap, iacv. With iacv plugged in, cannot get to idle below 1000 rpm even with using black ****. If I unplug iacv there is no difference. However with iacv unplugged, if I apply 12v to center pin and ground out lower/left pin which corresponds to white/ red wire of plug, car immediately drops rpm. Either test I still cannot shift in to gear without the rpms dropping too much and wanting to stall. Tps has been adjusted. If everything were functioning properlly , what should cold and warm idle rpm be?

 

How do I know if my XC90 volvo has had a timing belt change? Is it marked on the engine somewhere?

Also, do you kniw how I create a new post/thread?

Sorry to bother you on this?



Barrie