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Old 08-05-2019, 04:19 PM   #1
chrisweller2
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Default 86 Volvo 240 rough idle and intermittent stalling

Hello fellow enthusiasts
I've been working on my 86 245 (N/A) for about a year now. I've done a lot of work to it, including replacing floor plans, rocker panels, head gasket, brakes, harness... You get the point. Lately, I've been having issues where my vehicle will idle extremely rough until it inevitably stalls. Restarting results in an immediate stall. I can put it in gear quick enough and start driving around, but then it suffers from random, sometimes very severe hesitations. When I reach a stop my car may stay alive or it may decide to stall. If I'm cruising and I put it in neutral, the rpms will fluctuate greatly and occasionally the vehicle will stall.
I know my ignition system is good, I've replaced all plugs, wires, cap, rotor, coil, engine harness, and redone all of the groundings.
I've checked and rechecked for vacuum leaks.
I've verified both fuel pumps turn on and as a safety measure I've replaced my Fuel Pressure Regulator and my Fuel Pump Relay.
I've verified that I have sufficient pressure at my injector rail (80 psi).
I have not replaced my O2 sensors or my MAF.

I've looked at my spark plugs and they were very dark and covered in carbon residue. Prior checks before this situation showed a tan color.

Also, my exhaust fell off halfway through, leaving only my cat (which I believe I also hear my honeycomb spinning in) and the first muffler (resonator?). Could this cause a loss of backpressure which could in turn cause intermittent stalling and a volatile idle?

Thanks in advance for reading. Please let me know if I'm overlooking anything , or left out any information.

-Chris
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Old 08-05-2019, 07:02 PM   #2
dl242gt
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You may have something that is a bit more below the obvious stuff. Since it's intermittent you want to catch the car when it's happening. then you can use some troubleshooting to hopefully figure out if it's spark or fuel. I would suggest checking a few things.

The intank fuel pump can run. But if the hose is decayed then the fuel just splashes back into the tank. If you have about 3/8 of a tank or less. Listen at the fuel filler and if you hear splashing gas then you need to replace the hose for the intank pump.

The distributor hall sensor connector is easy to damage which can cause problems.
The coolant temp sensor is used by the computer to set mixture when the engine is in open loop. It can cause a very rich condition which causes stalling. If the connection or the sensor fail. The engine will never go into closed loop using the oxygen sensor. The black spark plugs lead me to tell you to check the sensor and wiring. Make sure you check it at three temps. The procedure is in the haynes or benley manuals or the green books.

Vacuum leaks can be sneaky. Check the bottom of the hose that goes from the air mass meter to the throttle body. The cracks start in the bottom where you can't see them. But they usually lean out the engine so the plugs would not show rich.
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Old 08-06-2019, 08:51 PM   #3
chrisweller2
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Quote:
Originally Posted by dl242gt View Post
You may have something that is a bit more below the obvious stuff. Since it's intermittent you want to catch the car when it's happening. then you can use some troubleshooting to hopefully figure out if it's spark or fuel. I would suggest checking a few things.

The intank fuel pump can run. But if the hose is decayed then the fuel just splashes back into the tank. If you have about 3/8 of a tank or less. Listen at the fuel filler and if you hear splashing gas then you need to replace the hose for the intank pump.

The distributor hall sensor connector is easy to damage which can cause problems.
The coolant temp sensor is used by the computer to set mixture when the engine is in open loop. It can cause a very rich condition which causes stalling. If the connection or the sensor fail. The engine will never go into closed loop using the oxygen sensor. The black spark plugs lead me to tell you to check the sensor and wiring. Make sure you check it at three temps. The procedure is in the haynes or benley manuals or the green books.

Vacuum leaks can be sneaky. Check the bottom of the hose that goes from the air mass meter to the throttle body. The cracks start in the bottom where you can't see them. But they usually lean out the engine so the plugs would not show rich.

Thank you for the response!
I've looked at the wiring again for the coolant temp sensor and confirmed everything is all connected. I recently replaced that sensor as well.

I had replaced the o-ring that sits between the fuel pump mount and the fuel tank, and while I was in there I didn't see anything out of the ordinary. I went ahead and listened for splashing and didn't notice anything unusual.

I unplugged the connector to the MAF to set the car into open loop and started it, and it did not stall out at all, granted the idle was poor. I let it run like that for maybe 45 seconds. After that I plugged it back in and started it and the car stalled immediately. I'm sure this isn't a sure-fire way to test out a MAF, but I found one for $32 on ebay that I could return so I reckon its worth the shot. I also have reason to believe that water may have gotten into my MAF so I am sure that may have caused damaged one way or another.

I've looked though all my vacuum hoses again and again because they have bitten me before so I don't want that to happen again. They also seem fine and secure.
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Old 08-06-2019, 08:58 PM   #4
2turbotoys
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A bad cat gets worse the hotter it gets.

If you have a multimeter you can check the idle air controller and MAF, I had a very hard to find random stalling issue on a 88 240, IAC ended up being the problem. Worth a look
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Old 08-10-2019, 06:06 PM   #5
Frank_Rizzo
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Not that I'm an expert on the subject, but I have a 1984 Volvo 244 that suffered the same symptoms. The key here is the stalling, poor running was intermittent, and only occurred in hot temperatures (ambient temp over ~95 F). The problem was the insulation in the wires of the wiring harness and ignition harness had decayed, exposing bare wires in places invisible to the eye. I replaced them and the problem went away.

The decaying wiring insulation in the wiring harness and ignition harness is a common problem up until the 1988 model year, from what I've read. There is a significant amount of literature available on the internet about this particular issue. It was a company-wide defect.
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