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86 Volvo 240 rough idle and intermittent stalling

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Joined: Fri Aug 02, 2019 10:22 am
Year and Model: 1986 Volvo 245
Location: MD

86 Volvo 240 rough idle and intermittent stalling

Post by chrisweller2 »

Hello fellow enthusiasts
I've been working on my 86 245 for about a year now. I've done a lot of work to I, including replacing floor plans, rocker panels, head gaskets, brakes, harness... You get the point. Lately, I've been having issues where my vehicle will idle extremely rough until it inevitable stalls. Restarting results in immediate stalls. I can drive it around my neighborhood once i start moving, but then it suffers from random, sometimes very sever hesitations. I can reach a stop and my car will not stall out, but sometimes it will. 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.

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.

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Re: 86 Volvo 240 rough idle and intermittent stalling

Post by 93Regina »

Disconnect computer's temperature sensor, and try it.
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Re: 86 Volvo 240 rough idle and intermittent stalling

Post by lummert »

80 PSI at the fuel rail? Don't you think this quite a bit too high when it should be about 43.5 PSI? Could there be a restriction in the return line?
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Re: 86 Volvo 240 rough idle and intermittent stalling

Post by 240gator »

chrisweller2, did you ever get anywhere on this issue? My 85 has similar symptoms. If I watch the boost gauge, the vacuum will dance slightly at idle where it spikes a few psi then settles then spikes then settles, etc. The spike is only a half second or so and occurs sort of randomly but let's say every 5-10 seconds. When in motion the car drives perfect. When I let off the pedal and coast, the car will die but only sometimes. I am gonna try the temp sensor and the fuel return line that were suggested.
1985 240 Turbo 310K | 1995 Yellow T5-R 236K | 1996 850 Turbo 225K | 2005 S40 2.4i 139K | 2005 XC90 2.5T 179K | 2007 S40 T5 141K
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