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Old 04-02-2014, 06:33 PM   #1
0x808080
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Default Surging Idle and Stalling when cold

Latest problem with my GF 1992 Automatic Volvo 240 is when she starts it in the mornings the idle will surge up and down... probably between 2000 and 1500 RPM in a weird cycle. This occurs when she has it in park. When she goes to drive away (or sits in Neutral) the engine stalls out.

IF she holds the gas pedal at about 5% (meaning just barely touching it) the car will still idle strangely in Park and when switched to any other gear will not stall out when she goes to drive away. It's like she is 'keeping it alive' barely by giving it a small amount of throttle.

After maybe 15 to 30 seconds it sounds like the computer takes over and can maintain its own Idle. Once this happen the strange idle cycling goes away.

The only thing we changed recently was all three front main seals and a tuneup meaning plugs, wires, rotor, and cap.
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Old 04-03-2014, 01:11 AM   #2
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Try another JY MAF...or unplug yours, and try it.

Check Fuel Pressure during this process, if there is a port to check it: Ford 90' Fuel Inj Adapter
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Old 04-04-2014, 11:09 AM   #3
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The 30-second delay before it works right is probably the car switching from open-loop to closed-loop operation.

Check/clean your IAC (idle air control) motor too. When the car has 0% gas pedal applied, a microswitch tells it to use the IAC system exclusively to keep the car running. Touching the throttle up to 5% opens the main throttle plate and would bypass a funky IAC system by letting air through the "normal" way.

I'm having a similar problem on my 940 that I just haven't had time to sort out yet - ****ty idle when on the microswitch with no gas pedal. I probably just need a new IAC motor, but I'm also told cleaning my throttle body may help. Just need a new throttle body gasket so I can take it off, clean it, and properly reinstall it.

I'd have fixed this ages ago but the 940 is not my daily driver, lol.
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Old 04-04-2014, 11:33 AM   #4
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Quote:
Originally Posted by slipstream3d View Post
The 30-second delay before it works right is probably the car switching from open-loop to closed-loop operation.

Check/clean your IAC (idle air control) motor too. When the car has 0% gas pedal applied, a microswitch tells it to use the IAC system exclusively to keep the car running. Touching the throttle up to 5% opens the main throttle plate and would bypass a funky IAC system by letting air through the "normal" way.

I'm having a similar problem on my 940 that I just haven't had time to sort out yet - ****ty idle when on the microswitch with no gas pedal. I probably just need a new IAC motor, but I'm also told cleaning my throttle body may help. Just need a new throttle body gasket so I can take it off, clean it, and properly reinstall it.

I'd have fixed this ages ago but the 940 is not my daily driver, lol.
Mine has started doing this while cold, I believe it's the IAC as well.
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Old 04-05-2014, 12:56 PM   #5
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Thanks for the replies - oddly I just cleaned the IAC with throttle body cleaner.

When the front main seals failed I thought it was a good idea to clean the PCV. So I cleaned that, while doing so I left the Throttle Position Sensor unplugged accidentally. The car would not idle at all and it was real bad. It sat for a day and I decided to just try a quick fix till I could figure out what was wrong. As a quick fix I wanted to just adjust the idle to be higher. I did that but then I noticed the TPS was unplugged. I adjusted the idle back to where it was. After that the car seemed to be fine. Then one morning the idle got all strange.

Should I unplug the MAF and then start the car? Do I want to do this when it is surging and stalling?
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Old 04-05-2014, 01:42 PM   #6
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Quote:
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Should I unplug the MAF and then start the car?
Why not...here read this thread. post 8

Btw, do you have LH3.1 ?
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Old 04-05-2014, 10:08 PM   #7
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Sounds like you need to adjust tps until it has continuity with no throttle applied. Not just so it clicks but so it actually has continuity between yellow white wire and ground. You should never "adjust the idle" on a lh2.4 car. That is done by the computer. These IACs get replaced often at shops but the reality is that they are pretty rugged and most idle problems seem to be tps related. Tps is what "turns on" IAC. This is most easily done with the throttle body on the bench. Clean the throttle then adjust the stop so there is just a halo around the throttle plate. Then adjust the switch so that you have continuity between terminal for yellow white wire and middle terminal on tps. If no continuity can be found TPS is bad(full of oil).
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