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  #1  
Old 08-29-2011, 01:04 PM
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1987 Volvo 740
 
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koriflame
Default Idle surging

My previous issue with the intank pump seemingly not running was resolved(I think) buy rotating the level sender 45 degrees. It was in there at what almost looked like upside down. It is now at 1/4 tank and doesn't sputter/fail to accelerate. Gas gauge seems accurate.

However, the next problem which I "believe" to be vacuum related is that when you start the car the tach will flare up close to 2000 then down to 500 then back to 1500 then down to 500, then to 1000, 500, 1500, 500, die. This was something going on before, only it wouldn't die. Neither the tach or boost stay 100% steady, they waver just a tad. one of the vacuum tubes is speckled with oil on the outside and the problem was bearable before I wiped it off. If this sounds like vacuum to anyone, would I just go to a parts store and ask for 4, 6, and 8 mm vacuum hoses and start replacing? Ive read tons of places that say check them or replace them but never with what or what sizes. This is really the first car I've been getting involved with maintenance wise, mostly because I love it and would hate to have to replaced it. I do have someone more experienced to help as long as I have information about the issue/diagnosis.

They do look a little cracked/stiff one is pretty soft though.
Once it gets going, it runs perfectly fine/normally.

Last edited by Koriflame; 08-29-2011 at 01:21 PM.
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  #2  
Old 08-30-2011, 10:57 PM
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koriflame
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Any thoughts? In addition it is very sluggish when first taking off, push the gas and it'll rev but feel like its being held back until its warm. Big difference between hot/cold idle.
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  #3  
Old 08-30-2011, 11:10 PM
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a gummed up idle air control valve would do what you say, assuming your car has one. pretty much all 240/740/940's do...

since you don't say what year/model car this is... its hard to be more specific.
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  #4  
Old 08-31-2011, 12:04 AM
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koriflame
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Sorry, that would be a 1987 740 turbo, should've remembered to say, my mistake. xD I'll look at that.
From the outside it looks like its never been touched, horribly filthy. I'm sure the inside is just as bad, will get on that tomorrow.

Last edited by Koriflame; 08-31-2011 at 12:24 AM.
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  #5  
Old 08-31-2011, 01:05 AM
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the idle air control is under the intake manifold, and has half-inch rubber hoses that connect to both sides of the throttle body.

the other candidate is a sticking/dirty throttle body thats not closing all the way. all this stuff gets gummed up, epsecially on turbos where they are subjected to both crankcase blowby, and turbo blowby. I'd take the throttle body off and clean it thoroughly with a safe degreaser like electronic contact cleaner, disconnect the hoses to the idle valve, and clean them too, and take the idle air control valve off the car and flush it thoroughly with the same cleaner. ideally, jumper it with 12V to open/close it so you can clean the flapper thing inside. then dry it all off (contact cleaner evaporates in seconds), and reassemble.
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  #6  
Old 08-31-2011, 01:44 AM
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Would the contact cleaner be safe to use with the TPS still in the throttle body? or should that be removed/replaced before & after the cleaning?
Stated here, Carb cleaner isn't http://www.swedishbricks.net/700900F...ce;%20Symptoms
By jumper you mean power straight from the battery... or?

Last edited by Koriflame; 08-31-2011 at 01:54 AM.
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  #7  
Old 08-31-2011, 01:59 AM
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you'll be able to do a better job cleaning it off the car... with that contact cleaner, you want to drench it and have it run off, while you brush off any grime that doesn't just melt away. on the manifold, all that crud will end up inside the manifold...

re: power, that or any other source of 12VDC (8 AA cells, etc etc). pin 1 is +, pin 2 is ground. the ECU pulses it with a variable duty cycle to modulate the idle speed.

another thing to check is that the idle switch on the side of the throttle body is closed when the throttle is at idle, and opens within a degree or two of throttle plate movement.

your car is probably LH2.2, I'm more familiar with LH2.4 systems, but they are fairly similar in many aspects.
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  #8  
Old 09-05-2011, 12:10 PM
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Cleaned the IAC and it's definitely better, but not cured. Hasn't died on idle since, will check the switch and clean the throttle body next. Idles a lot smoother now as well.
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  #9  
Old 09-14-2011, 10:33 PM
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Is there a way to tell if the IAC is just crap? Shifting from park to drive or reverse drops the rpms down to 400 for a moment where it sounds like it'd die if it went any lower. I still havent gotten to the throttle body. I don't want to pay their $11 shipping just for their(fcp) 75 cent gasket.
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  #10  
Old 09-21-2011, 10:45 PM
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the skinny hose on the FPR is vacuum, there shouldn't be any fuel there.

what you need to do is connect a fuel pressure gauge with a T to the other end of the fuel rail where the fuel line goes into it, then start the engine and read the actual fuel pressure, which on a LH2.x car should be about 42PSI above manifold pressure (with idle vacuum of about -7psi, that would be about 35psi absolute).
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  #11  
Old 09-22-2011, 09:54 AM
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Since it's a turbo, it's a good guess you have bad rotted vacuum hoses as well. The vac hoses also hold positive pressure under boost so they do double duty. Many of these vac leaks are all but undetectable. To get the car back to a stage zero, I choose to replace ALL rubber hoses under the hood. This includes the booster hose, flame trap hoses and IAC hoses. Turbo cars produce a fair amount of under hood temperatures...after a few decades it just makes sense to me. Consider replacing the vac hoses with silicone hoses. They are essentially impervious to the temps and oil fumes.
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  #12  
Old 09-22-2011, 07:30 PM
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Thanks, I'm going to try those. What all can cause it to start and die and idle rough when cold. When i got it I did a tuneup, fluids, plugs, wires, fuel filter, air filter, but didn't have the money for a cap/rotor. Kind of a longshot, but any chance the one tuneup item I didn't replace contributes to the issue? I'm going to be ordering a TB gasket along with brake pads soon, so I'll FINALLY get to cleaning that. I got curious and checked both the vacuum line and fuel return on the FPR. There was fuel and there was vacuum, not sure how much fuel it pushes at idle, but there was some. I also cleaned the MAF, to no avail. My next thoughts besides the vacuum would be that the IAC isn't functioning properly. Try a new cap/rotor. get the injectors cleaned. Maybe knock sensor? I think it has a bit of a tick, might be mistaken for the loud injectors... not sure.

Last edited by Koriflame; 09-22-2011 at 07:40 PM.
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  #13  
Old 09-22-2011, 07:40 PM
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the crank position sensor wiring could be crapping out on you, this is behind the engine, and reads off the flywheel.
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  #14  
Old 09-22-2011, 08:18 PM
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koriflame
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This is the crank position sensor?

exhaust side - the wire felt okay all the way up.
Click the image to open in full size.

But... that wire runs to an empty connecter that was capped above the valve cover? Is this right?

Click the image to open in full size.
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  #15  
Old 09-22-2011, 08:29 PM
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actually, hmmmm. on an 87 turbo 740, it looks like the position sensor is inside hte distributor. its moved back and forth a few times. I can't quite tell what that first picture is showing.
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  #16  
Old 09-22-2011, 08:43 PM
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A sensor directly to the left of the oil filter, which I thought might be it.
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  #17  
Old 09-22-2011, 08:57 PM
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Turbos didn't get a crank sensor per se until 90...you have a Hall sensor in the distributor but I'll tell ya straight up...an old turbo car without proper, ongoing maintenance is gonna have vac leaks out the wazoo. The extra heat, oil vapor and positive pressure in the lines rots 'em out. Check for leaks w/ a can of carb spray or use propane...until you do the routine stuff and get it out of the way, the rest is a snipe hunt. You will be amazed how dirty your TB is when you get it off most likely. I've seen the throttle blade so nasty it would not close! And...if it doesn't close, the TPS won't kick in. That's something to investigate when you pull the TB for cleaning; the TPS adjustment is critical to proper idle.
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  #18  
Old 09-22-2011, 09:15 PM
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ah, right, the crank sensor is on LH 2.4, isn't it, and Turbo was LH 2.2 through 89?
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  #19  
Old 09-22-2011, 09:34 PM
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Si...
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  #20  
Old 09-22-2011, 09:47 PM
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I bought the hoses, where does the one on the intake manifold that runs through the firewall go?
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Old 09-22-2011, 09:47 PM
 
 
 
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1990, 240, 740, air, check, climate, control, fast, idle, location, surge, surges, surging, valve, volvo


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