SOLVED: 1998 S70 base - rough idle, odor, undrivable (culprit was distributor cap) Topic is solved

[MagicBus]

Hello, all

I'm at a loss on this one. I have a 1998 S70, 213,000 miles. I've had the car since September, 2016, when I purchased it at 199,XXX miles. At the time, I did a full ignition tune-up but not the timing belt (not due for another 20K miles).

The car's been running fine - perfectly, I'd say. My wife and I even drove it round trip from Massachusetts to Kentucky a few weeks back (approximately 2000 miles total) and it didn't skip a beat. I was driving the car in to work this morning, when I came to a stop for traffic. Without any warning, the car started idling roughly. When it didn't clear up on its own in a few seconds, I decided to pull the car over into the breakdown lane.

The idle got worse quickly. When I put the car back into gear (automatic - probably should have mentioned that earlier), it bucked, moved forward maybe a few feet, and then died. I popped the hood and didn't see anything obviously amiss. The transmission fluid and engine oil were clearly there on the dipsticks, and I didn't see anything wrong with the coolant level.

I was able to restart the car repeatedly, but it was hard to start and idled roughly. Same behavior when I tried to move the car forward, so it wasn't a one-time phanton malfunction. It was 20º F this morning, so I decided to try to let the car idle a while so I could get some heat. I let the car idle a few minutes and the check engine light came on, and then started blinking. I also noticed a slight sulfur smell. I shut the car off and grabbed my code reader (I always carry it in my daily driver). The codes I got were:
P0300 (random/multiple misfire)
P0301 cylinder 1 misfire
P0302 cylinder 2 misfire
P0304 cylinder 4 misfire

As I had a P0300, I wouldn't have been surprised if I'd let it run a little longer and it had also thrown a P0303 and P0305, but that's just speculation.

I got towed home and drove one of my other cars into work. Tonight, the Volvo started again (with effort) and displayed the same behavior in my driveway. So the car behaves the same way up to temperature and when ice cold.

I'm thinking it's a fuel or a spark problem. I've been searching online, thinking that the sulfur odor may be key to understanding this. What I can't seem to figure out is if that means (at least, as far as the catalytic converter is concerned) the car is running rich (too much fuel) or too lean (not enough fuel). If raw fuel is getting to the cat, then I'd start looking at the ignition coil (probably original to the car, and possibly going wonky before it quits completely?) first. I don't suspect any of the other ignition system components (yet), as they're all low mileage and I remember buying quality parts.

If the car is misfiring because the cylinders aren't getting fuel, then I'd start looking at the fuel pump relay and fuel pump.

Does anyone have any insight into this??? Thanks in advance.

[kahl]

Disconnect the MAF sensor on the pipe leading from the air box and see how the car operates. Your symptoms are classic MAF sensor failure.

[abscate]

Diagnose the fuel side by looking at fuel pressure o n the rail with a gauge. Fuel pump relays and fuel pumps usually start going to 200k miles

Check your spark by pulling a plug and looking for the blue snap with the plug grounded.

With all the plugs pulled, a compression test will give you indication of the condition of your motor.

Finally, a big vacuum leak will cause all those symptoms, too. Inspect all the larger hoses for splits, holes, taps, things fallen off.

[RickHaleParker]

You listed most of the symptoms of a clogged exhaust system.

Tap on the catalytic converter with a rubber mallet, does it rattle?
Do the same with the pipes, resonator and muffler.

After warmup, will the engine rev to 5K?

Any whistling coming from under the car?

Back pressure can cause the engine to misfire on all cylinders.
Three causes of sulfur smell. catalytic converter, engine running too hot, excess fuel.
On excess fuel, if it misfiring on all five ... fuel pressure regulator.

[MagicBus]

Disconnect the MAF sensor on the pipe leading from the air box and see how the car operates. Your symptoms are classic MAF sensor failure.

I'll try that and report back.

[MagicBus]

Ideally, I'd be scientific about it. But, without all the proper equipment to test stuff, and with the need to get the car back on the road fast in poor weather, I may need to narrow things down and just throw some parts at it.

Diagnose the fuel side by looking at fuel pressure o n the rail with a gauge. Fuel pump relays and fuel pumps usually start going to 200k miles

A few problems - I don't own a fuel pressure gauge, I wouldn't know how or where to hook one up, and I don't know the specs for a properly operating system.

Check your spark by pulling a plug and looking for the blue snap with the plug grounded.

Nothing wrong with this suggestion. I may try this.

With all the plugs pulled, a compression test will give you indication of the condition of your motor.

I'll save this for later. I do own a compression gauge, but the engine's been performing flawlessly, and I don't need to add any oil between oil changes. I wouldn't suspect that kind of sudden engine failure (at idle) without some kind of obvious event to cause it.

Finally, a big vacuum leak will cause all those symptoms, too. Inspect all the larger hoses for splits, holes, taps, things fallen off.

When you say "larger" hoses, what are you referring to? I've been working on these cars now for just over four years (we have a 1998 S70 and 1998 V70), but I'm not intimately familiar with the vacuum system.



Thanks for the suggestions.

[MagicBus]

You listed most of the symptoms of a clogged exhaust system.

Tap on the catalytic converter with a rubber mallet, does it rattle?
Do the same with the pipes, resonator and muffler.

After warmup, will the engine rev to 5K?

Any whistling coming from under the car?

Back pressure can cause the engine to misfire on all cylinders.
Three causes of sulfur smell. catalytic converter, engine running too hot, excess fuel.
On excess fuel, if it misfiring on all five ... fuel pressure regulator.

The thought had occurred, but is it possible to have such a sudden, spectacular failure of the exhaust system so quickly without any symptoms at all prior to the failure?

[abscate]

No, clogged exhausts are rare as are clogged fuel filters

These are non turbo cars, right? Inspect the air hoses after the MAF for things that are loose , holed, split, etc.

Any air that gets in after the MAF is unmetered and will cause bad running.

If you aren't in a rush I might be driving by next week with kit, later in week,,,,maybe Thursday

You test fuel pressure at the fuel rail, look for a schrader valve ( bicycle wheel valve) and use a 1 dollar pencil tire gauge which you throw away afterwards.

[MagicBus]

No, clogged exhausts are rare as are clogged fuel filters

That's what I figured, but am not opposed to checking those.

These are non turbo cars, right? Inspect the air hoses after the MAF for things that are loose , holed, split, etc.

Any air that gets in after the MAF is unmetered and will cause bad running.

OK - that points me in a direction. Will check. And yes, both are base model, non-turbo.

If you aren't in a rush I might be driving by next week with kit, later in week,,,,maybe Thursday

Kit - link or description, please? I am in a BIT of a rush. I have another car I can drive in a pinch, but it's unsuited to cold weather travel and driving in the snow.

You test fuel pressure at the fuel rail, look for a schrader valve ( bicycle wheel valve) and use a 1 dollar pencil tire gauge which you throw away afterwards.

I do know where that valve is, so that would be a good way to test. Any idea what the spec should be at idle?


Thanks, and thanks everyone so far.

[RickHaleParker]

it possible to have such a sudden, spectacular failure of the exhaust system

Exhaust system failures can appear to be sudden, once the condition produces enough back pressure. Material from resonators and mufflers can act like a rag getting sucked into the system.