Stalling when coming to a stop, need help

[FireFox31]

Now the engine is smoking. My girlfriend swapped in a new cylinder 4 coil and started the engine. She saw a moderate amount of smoke coming from behind the engine, thus immediately shut it off. This smoke wasn't present a few days ago when she started the car maybe six times with different coils unplugged to test them. We stopped work after this because it was dark out.

There is a giant hole in the front of the center muffler. It's a stretch to suggest that exhaust came from that up to the rear of the engine bay. Maybe this smoke is revealing the air leak which is causing the rough idle. I can have her start it again tomorrow but I'm nervous about that smoke.

She needs it for work starting Tue. Rental car could work, but that cost me a bunch last week. There's a local dealership tech I'm trying to have come look at it, but that's a long shot. I could have it towed to the only shop I trust, but they might not have availability to fix it. We'll see once these pesky holidays are past. Thanks again for your input.

[MoVolvos]

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The smoke could be unburned fuel and perhaps blowby. When the coil was not working fuel washed down the cylinder wall and the rings are clean without lubrication. Now that you have ignition perhaps the fuel and oil going by the piston rings is causing the smoke. If it's running kind of normally but smoking only, you may have to let it run for just a bit before the smoke clears. My guess on this!
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[abscate]

Did the coils solve the rough idle problem?

Can she drive an easy to handle P2 stick shift? I’m out of country mid Jan so don’t need my P2 until end of month, maybe I can get up to have a look and leave the P2 worst case?

I too, guess that smoke is unburied fuel. Idle for 15 minutes , evaluate

[FireFox31]

Thanks for the advice about the smoke, both of you. How could the smoke be coming out of the system? I assumed the tail pipe or a leak were the only exit points.

I will have her replace coil 5 (having already replaced 4) and let it idle for a bit. After replacing 4, it ran such a short time that she couldn't tell if it was better.

Can she drive an easy to handle P2 stick shift? I’m out of country mid Jan so don’t need my P2 until end of month, maybe I can get up to have a look and leave the P2 worst case?

That's a very generous offer. Unfortunately, she can't drive stick. I've got a plan to have the car towed to the local Volvo specialist. Hopefully he has availability to help. But, she'll replace all five coils first. Though I thought Geronimo wasn't good enough for new coils, I now realize that the passenger is.

[abscate]

When you muck around under the cover it’s easy to dislodge sludge onto the exhaust manifold and cause smoke. If it’s just wisps m don’t worry about it.

[FireFox31]

This car has two small gaps beneath the exhaust manifold which I think lead directly into cylinders 3 and 4 exhaust ports. That could be where the excess unburned fuel came from. The smoke could have also been oil, which this car burns a decent amount of.

So the presence of smoke could be a good sign, showing that the plug is getting spark. We'll replace the other coils tomorrow and see how it runs. Thanks again for doing all of the thinking, everyone. I've got no thinking to spare at the moment.

[FireFox31]

Replacing the coils improved engine performance but there's still a problem. My girlfriend drove the car and got these data:
With gas applied, the car runs fine.
Coasting above 35 mph, the car runs fine.
Coasting under 35 mph, the tachometer drops to 500 threatening to stall and engine runs rough/shaking. The orange shift arrow may light.
At idle (in D or N), tachometer returns to 1000 rpm but engine runs rough/shaking. The dash lights and headlights flicker.
When the car stalls, it requires 30-60 seconds before it will restart.

My old 2000 V70 NA manual had stalling when stopping. I think it's also happening to my other 2000 NA automatic. Both occurred only in cold temperatures. My girlfriend tried the 1995 850 computer relearn procedure but it didn't help.

I've previously noticed the tach drop to 1000 when coasting, but only at certain speeds or in certain gears. In my other 2000 V70 NA auto, I think the tach always stays at the current wheel/engine speed when coasting. I don't know which is correct. I never felt power loss when coasting in either automatic.

I'll have the car towed to the Volvo mechanic tomorrow night, hoping he can look at it soon. Any thoughts on the resolution would help. Thanks as always.

[MoVolvos]

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How is your car doing and did any of the following help? An exhaust leak, unless it's at the manifold shouldn't make the car run that rough. The smoke is another rabbit hole so don't focus too much on that with the rough running.

1) Clean ETM
2) Swap or replace coil?
3) Change or swap out plugs?
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[FireFox31]

I cleaned the ETM about two years ago when installing it. I can't ask my girlfriend to clean it again, that's a bit much.
She replaced all five coils with new Bosch. That improved engine running but didn't solve the rough idle (misfire) or low tach under 35 mph.
I didn't have her swap the spark plugs. I might order a set and the tools for her to try if it takes me too long to get in to the mechanic.

Is there some air intake system which is only active under 35 mph? Maybe that's what has failed, leaking or clogged only when active.

[dikidera]

When you muck around under the cover it’s easy to dislodge sludge onto the exhaust manifold and cause smoke. If it’s just wisps m don’t worry about it.

This is so true. After replacing headgasket and re-installing the exhaust manifold and starting the car it smoked a lot I was actually deahtly afraid I made a mistake. Turns out when you handle the exhaust manifold with dirty oily gloves it happens and can smoke for a good few minutes.