IAC problem......I think
#1
IAC problem......I think
My '91 740, non turbo, Regina starts fine, idle's fine and runs fine. But when I let off the gas and it decelerates the rpms dip so low it either dies or almost dies. My first thought was the idle control valve, which I cleaned and checked for smooth movement by manually forcing the plunger down. No problem and the spring loading seems to work when I release it. Hooked it back up and same problem. Applied 12 volts to the terminals, and could hear it click, so I didn't think that was my problem. All the threads I've searched about IAC's seem to be stuck open and have high idles. Pulled mine out again and gave it 12 volts while I looked down the valve and again it clicked but just barely and quickly moved a little and returned to the close position. Question: as long as power is applied should it continue to stay open? Or is it a pulsing action - open...close...open?
#2
#3
Yes, I made sure the polarity was right. In fact, the valve has + and - markings near the terminals. So I guess mine is shot. Makes sense. Thanks
#4
Well this is embarrassing, but good news in a way. I was using my 12v test light as my positive jumper lead and, like I said, getting a click with very little, temporary movement. Out of curiosity I used a straight wire right off the battery and it made a loud click and stayed open. I guess running through the light dropped the voltage enough to affect the valve. I checked the voltage coming from the connector and I'm getting 12 volts but when I hooked it up with the ignition on, engine not running, again I got just a little movement and wouldn't stay open. So I tried using the positive lead from the connector and grounding the negative lead to the engine. And it worked, which told me the negative lead of the connector wasn't a good ground. So, finally, I plugged all the vacuum hoses, connected the valve to it's connector and started the engine. I watched inside the valve as I revved and slowed the engine and it responded the way it should. I guess it's very sensitive to having the right voltage going to it. Anyways, it seems ok now but I will have to check that rpm drop during deccelaration tomorrow when there's more light.
#5
with the idle valve disconnected, the engine fully warmed up, and all accessories shut off, it should idle about 500rpm in neutral/park. turning on a/c, putting it in gear, etc can stall it without the IAC connected. connecting the IAC should bring the idle up to 600-700rpm on a fully warmed up engine, and it should maintain that 600-700 when you put it in gear, switch on the a/c, etc.
#7
#8
with the idle valve disconnected, the engine fully warmed up, and all accessories shut off, it should idle about 500rpm in neutral/park. turning on a/c, putting it in gear, etc can stall it without the IAC connected. connecting the IAC should bring the idle up to 600-700rpm on a fully warmed up engine, and it should maintain that 600-700 when you put it in gear, switch on the a/c, etc.
Last edited by Moetheshmoe; 11-22-2016 at 06:23 PM.
#9
13.5V is actually on the low side, at least if your battery is fully charged and its not freezing cold out.
at 68F/20C, a fully charged battery should be about 12.6V at rest (eg, an hour or two of sitting off), and with the engine running but all accessories off should be 13.8-14.2V
I dunno jack about the Regina system, they were never sold in California.
at 68F/20C, a fully charged battery should be about 12.6V at rest (eg, an hour or two of sitting off), and with the engine running but all accessories off should be 13.8-14.2V
I dunno jack about the Regina system, they were never sold in California.
#10
13.5V is actually on the low side, at least if your battery is fully charged and its not freezing cold out.
at 68F/20C, a fully charged battery should be about 12.6V at rest (eg, an hour or two of sitting off), and with the engine running but all accessories off should be 13.8-14.2V
I dunno jack about the Regina system, they were never sold in California.
at 68F/20C, a fully charged battery should be about 12.6V at rest (eg, an hour or two of sitting off), and with the engine running but all accessories off should be 13.8-14.2V
I dunno jack about the Regina system, they were never sold in California.
Last edited by Moetheshmoe; 11-22-2016 at 08:37 PM.
#11
in my experience, occasional misses are usually ignition. fuel delivery problems generally materialize as stumbles or power loss at high throttle, upper middle RPM in taller gears when the engine is working its maximum.
it is possible, I suppose, that you have 1 or more injector with a bad spray pattern, thats possibly dribbling fuel too. but that would more likely affect idle smoothness.
you could try the italian tuneup. next time you're near empty, add a medium size can of Techron (even better, use an 11 oz can of BG 44k) to the tank, and only put a few gallons of fuel in, no more than a half tank. then get out on the freeway, leave the car in third gear to keep the RPMs high, and run that tank close to empty, driving like you stole it.... yes, I know, this is 100 or more miles of driving for no purpose. refill the tank, and do an oil change fairly shortly after this as you likely blew a bunch of crud into the oil.
it is possible, I suppose, that you have 1 or more injector with a bad spray pattern, thats possibly dribbling fuel too. but that would more likely affect idle smoothness.
you could try the italian tuneup. next time you're near empty, add a medium size can of Techron (even better, use an 11 oz can of BG 44k) to the tank, and only put a few gallons of fuel in, no more than a half tank. then get out on the freeway, leave the car in third gear to keep the RPMs high, and run that tank close to empty, driving like you stole it.... yes, I know, this is 100 or more miles of driving for no purpose. refill the tank, and do an oil change fairly shortly after this as you likely blew a bunch of crud into the oil.
#12
I did do a half-Italian tune up - a bottle of Techron and just a few gals of gas but didn't run it in 3rd gear for that long but I also ran half a bottle of seafoam thru the tank and the other half thru the throttle body. So, if it is ignition, what could it be?
BTW, I also adjusted the TPS so it clicked going to open throttle and closing. But I've read some info that says it should also click at full, open throttle and mine does not. To test it you're suppose to ground either side connector to the center one and the idle should return to normal. Grounding one side connector does that but grounding the other does not? What kind of signal to the ecu does the TPS send? Also, I noticed this morning that my cold idle is about 800 to 850 rpm and drops to 750 when warm. And when it is in that slightly higher rpm I can release the throttle from 2500 rpm and it doesn't do the low dip and stall. Does this mean my mixture when warm is too lean?
BTW, I also adjusted the TPS so it clicked going to open throttle and closing. But I've read some info that says it should also click at full, open throttle and mine does not. To test it you're suppose to ground either side connector to the center one and the idle should return to normal. Grounding one side connector does that but grounding the other does not? What kind of signal to the ecu does the TPS send? Also, I noticed this morning that my cold idle is about 800 to 850 rpm and drops to 750 when warm. And when it is in that slightly higher rpm I can release the throttle from 2500 rpm and it doesn't do the low dip and stall. Does this mean my mixture when warm is too lean?
Last edited by Moetheshmoe; 11-23-2016 at 11:46 AM.
#13
in my experience, occasional misses are usually ignition. fuel delivery problems generally materialize as stumbles or power loss at high throttle, upper middle RPM in taller gears when the engine is working its maximum.
it is possible, I suppose, that you have 1 or more injector with a bad spray pattern, thats possibly dribbling fuel too. but that would more likely affect idle smoothness.
you could try the italian tuneup. next time you're near empty, add a medium size can of Techron (even better, use an 11 oz can of BG 44k) to the tank, and only put a few gallons of fuel in, no more than a half tank. then get out on the freeway, leave the car in third gear to keep the RPMs high, and run that tank close to empty, driving like you stole it.... yes, I know, this is 100 or more miles of driving for no purpose. refill the tank, and do an oil change fairly shortly after this as you likely blew a bunch of crud into the oil.
it is possible, I suppose, that you have 1 or more injector with a bad spray pattern, thats possibly dribbling fuel too. but that would more likely affect idle smoothness.
you could try the italian tuneup. next time you're near empty, add a medium size can of Techron (even better, use an 11 oz can of BG 44k) to the tank, and only put a few gallons of fuel in, no more than a half tank. then get out on the freeway, leave the car in third gear to keep the RPMs high, and run that tank close to empty, driving like you stole it.... yes, I know, this is 100 or more miles of driving for no purpose. refill the tank, and do an oil change fairly shortly after this as you likely blew a bunch of crud into the oil.
#14
#16
Pierce, what's your thoughts on this? My problem has returned but not due to the same root cause. Initially, my manifold pressure sensor wasn't holding vacuum but now it does and I checked the varying voltage signal it puts out depending on vacuum and it's fine. Same with the temp sensor in the airbox. In fact, the car drove well for the last week with just occasional rpm dips but not enough to kill the engine. An hour ago, I went for a test drive and at stop signs, idling in drive it dipped and died 3 times in 2 blocks. I finally got a code 2-2-3, Signal missing to/from idle valve. The valve itself looks fine. I hook it up to the battery and it clicks and holds no problem. I double checked the TPS and it seems it's adjusted properly. With the connector off I got it started and it ran at 500 rpm barely, as it's suppose to. So I hooked my meter to the connector, and it shows 12.5 v with engine off and 13.5 with engine running. I revved it up, off idle, and it still showed 13.5 v. That's what confuses me. I thought it stopped activating the IAC valve off idle? Should it still be sending a signal? Or maybe voltage is constant and the ground disconnects? And here's the strange thing, after dying 3 times, the most it's ever done, I hooked everything back up and now it runs perfect! The tach needle is rock steady with absolutely no surging or dipping. Could I have a loose ground somewhere? Could the ECU be failing? I'm lost.
#17
Funky wiring, maybe ? I dunno, I've never even seen a Regina system, much less worked on one. All California Volvos were Bosch.
re your voltage readings, yeah, most of those systems, one pin is hooked up to power, and the other pin is intermittently grounded to actuate whatever it is. this 'grounding' is via an NPN power transistor in the ECU, a circuit commonly known as 'open collector' in electronics.
re your voltage readings, yeah, most of those systems, one pin is hooked up to power, and the other pin is intermittently grounded to actuate whatever it is. this 'grounding' is via an NPN power transistor in the ECU, a circuit commonly known as 'open collector' in electronics.
#18
Funky wiring, maybe ? I dunno, I've never even seen a Regina system, much less worked on one. All California Volvos were Bosch.
re your voltage readings, yeah, most of those systems, one pin is hooked up to power, and the other pin is intermittently grounded to actuate whatever it is. this 'grounding' is via an NPN power transistor in the ECU, a circuit commonly known as 'open collector' in electronics.
re your voltage readings, yeah, most of those systems, one pin is hooked up to power, and the other pin is intermittently grounded to actuate whatever it is. this 'grounding' is via an NPN power transistor in the ECU, a circuit commonly known as 'open collector' in electronics.
Last edited by Moetheshmoe; 12-05-2016 at 07:18 PM.
#19
on the 1991 Regina 740/940, it looks like pin 1 of the IAC gets power from the fuel system relay pin 87/1, and IAC pin 3 goes to ECU pin 33 to be intermittently grounded (via said NPN open collector inside hte ECU).
the IAC power circuit goes through connector D pin 3 (green or blue/yellow), and the ground circuit goes through connector D pin 1 (red/black)... this connector D is one of two 8 pin connectors through the firewall behind the right wheel housing/strut tower.
the IAC power circuit goes through connector D pin 3 (green or blue/yellow), and the ground circuit goes through connector D pin 1 (red/black)... this connector D is one of two 8 pin connectors through the firewall behind the right wheel housing/strut tower.
#20