'93 850 Dies During Idle Topic is solved

[Samusai]

1993 850 N/A
Automatic Transmission
250k miles



Hey guys, it's been a while since I've been on the forum but I've run into an issue I cannot figure out so I come here for guidance. I'm trying to get my old 850 back into driving shape. The car has mostly sat for the last 1.5 years so I'm going through it's issues in the hopes of getting her back on the road. The issue I cannot figure out is the dying issue it has during idle. I'll start the car and let it sit idle, and after 7-8mins of it warming up the engine's revs will dip a few times until it ultimately dies. I've linked a video I shot of this. Hopefully that helps clarify what I mean. If I manually apply the gas pedal to 1500rpm or so the car will run just fine but as soon as I let off the gas it will go into it's sputtering and die. Also, once this happens and the car dies, I cannot get it started again until I let it sit for an hour.

Here's what I've done so far to try and fix things:
1) Checked for vacuum leaks. I only found a small one at a rubber elbow behind the vacuum tree. Replaced it.
2) Drained the old fuel, put new gas in, and replaced the fuel filter.
3) Checked the fuel pressure with engine running. Although I can't remember the exact number the fuel pressure did remain steady and didn't dip during the engine's stuttering. Assuming fuel pump is good.
4) Cleaned Idle Air Control Valve. This didn't fix the problem so I ordered a used replacement off ebay that was listed as "good, working condition". Put the replacement on...same issue. Cleaned replacement IAC to no avail. Assuming IAC is not the problem.
5) Cleaned the MAF sensor with the appropriate cleaner and at first I was hopeful because the car ran for at least 15min with no problems before I turned it off. Next start, however, and the dying issue was back.

The last attempt made me suspect the MAF sensor so I've tried a few things aimed at it. If I unplug the MAF cable, the car will not start and it throws a 1-2-1 code (MAF sensor signal). Also, if the car is running and I pull the cable it will immediately die and throw the same code.

Any thoughts? I've tried to be pretty descriptive with the problem so sorry for the wall of text above

Thanks much!
Sam

**edit 9/25, I incorrectly listed the 121 code with a transmission code. It now correctly states MAF sensor signal

[rspi]

Coolant temp sensor.

[misha]

No other codes from ports?
If ect is bad like rspi suggested....the car would run very rich and cooling fan would run all the time...if it would be even able to start at all....and bad ect would throw a code....UNLESS it's aftermarket s*it

Btw...the car should start and run with maf unplugged....you said that yours will not start with maf disconnected.

[Samusai]

Thanks for replying all,

Only other codes are a few random ones from A7 (Trip Computer) and A3 (ABS). No codes from A2 (Fuel System) or A6 (Ignition).

The cooling fan only kicks on when the engine comes to temperature. I have to hold the throttle open and rev the engine at 1500 rpm but when the temp gauge reaches approx. halfway the cooling fan does come on. I've never replaced the coolant temp sensor so I don't know what brand it is. (Agreed that aftermarket parts aren't the way to go).

...and yes, the car will not start with the maf unplugged. When I try this it throws the 1-2-1 code (A2) MAF sensor signal...which I would expect.

[kcodyjr]

After it stalls, pull a spark plug. Check to see if it's wet or dry.

If it's wet with fuel, it's running overly rich, and/or you aren't getting sufficient spark. First, check the air filter isn't plugged. Then, reset the adaptives (disconnect battery cables and short together for 10 seconds). If you're still having the symptom, and no other codes, I'd suspect leaky injector seals. The other explanation, O2 sensor, should throw a code.

If it's dry, it might be starving for fuel. Put some Techron in it and take it out for a drive, maybe your injectors are varnished up after sitting for so long without fuel stabilizer. If so, you may need to pull them out and send them off for refurb. Also, you could have a marginal fuel pump relay or master fuel injection relay, but it's an odd coincidence that it ALWAYS stumbles when you try to idle. A bad relay should be entirely bad or maddeningly intermittent, but not predictable like that.

Did you rule out an ignition issue? After sitting like that, the distributor cap and rotor might be badly corroded.

[Samusai]

After letting the car run for 15mins I pulled spark plug #1 to take a look. It had a little fuel on the electrodes but not so much to lead me to believe it's running incredibly rich. In 2013 it did have a running rich problem that ended up destroying the catalytic converter. After replacing the cat, I also sent the injectors to Rich at CruzinPerformance in 2013 for cleaning and new o-rings. Also replaced the fuel pressure regulator and O2 sensor at the same time. It's possible the injectors are partially clogged again, so I'll keep that in mind.

Just checked the cap and rotor, and they look good. I did a tune up in early 2014 where I replaced the cap, rotor, plugs, and air filter (all OE parts).

I went ahead and ordered a Volvo coolant temp sensor since that's one part I have not replaced since I've owned the car so I figured I might give that a shot. I'll update this post once I've replaced it.

Thanks all,
Sam

[Samusai]

Whoops, also noticed I had left the linked Youtube video as private. It's now public and open for viewing. Skip to about the 8min mark for the rough idle.

[JimBee]

My '93 behaved like that. I think I replaced the MAF to fix it.

[misha]

What you mean about OE parts....OEM right?
Sensors,cap,rotor,cables....they MUST be OEM...otherwise these cars will not run properly....if they would run at all.

[kcodyjr]

OE = original equipment. This could mean "what the car left the factory with" and it could mean "Volvo blue box parts".

OEM = original equipment manufacturer. This is when you buy the exact same distributor cap but in the Bosch box.