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  #1  
Old 08-29-2011, 01:04 PM
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1987 Volvo 740
 
Join Date: Jun 2011
Location: Janesville, WI
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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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1987 Volvo 740
 
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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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1992 Volvo 745
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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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Old 08-31-2011, 12:04 AM
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1987 Volvo 740
 
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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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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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1987 Volvo 740
 
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koriflame
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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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Old 09-05-2011, 12:10 PM
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koriflame
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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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1987 Volvo 740
 
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koriflame
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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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Old 09-21-2011, 10:45 PM
 
 
 
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Tags
1990, 240, 740, air, check, climate, control, fast, idle, location, surge, surges, surging, valve, volvo


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