Car stranded, again, misfire help - 99 s70 na m56 Topic is solved

[smacknab]

Hi again everyone, I just got back from a 3 week work trip and was driving the lady to work when the engine started chugging and for a little while produced a burning smell somewhat like fireworks. At idle the engine produces more aggressive vibrations than normal. I pulled over and checked the codes, getting a p0303, which I found on MVS to be a misfire in cylinder 3 (car also pulls codes 1041 and 1081 consistently), also my ets light has been coming on and off I get idle dips when coming to a stop in nuetral. But that last stuff has been happening for a while.

Sooo I pulled the p0303 and checked the forums here and it was suggested to disconnect the fuel-injector wiring and see if it made a difference. That led to no difference in the running of the car, but I'm still confused as to what I should do from here. Does this mean I replace one injector? Or one coil pack? Do I need to any of the wiring as well? I'm about 15 miles from home and I read running the car with a misfire is no good, so I'm gonna tow the car home, but I'm hoping for advice on other checks I can do, and a possible order of operations.

The car has 208k miles, I recently redid the head gasket and it's been running fine for about 1.5 months (minus the ETS issue). As far as I know the injectors, ignition coil packs and wiring are all original, but I'll check the service records when I get home. I put in new spark plugs about 4 months ago when I got the car.

As always, thanks for the help.
Sean

Other notes:
-the chugging seems to happen at idle, then smooth out between 1500-2000 rpm, then chug/vibrate again over 2000 rpm
-i checked the wiring, and there's nothing that's popping out to me, especially on injector 3 and cool pack 3 the wiring looks mostly fine

[smacknab]

Thankful for AAA today

[smacknab]

This is spark plug 3 which was giving the code. I swapped it with plug 2 (looked about the same) and the engine still ran rough. I then swapped the coil packs 2 and 3 and still running rough. Now it's giving me p0300 (seems to be multiple misfires).

My suspicion at that point was the coil pack (originally 3rd cylinder, now on the 2nd cylinder). I then went and pulled the fuel injector wiring on each cylinder, one by one starting the car and testing the idle in-between. The car seemed to run best with the injector wiring #2 pulled, so I think the culprit is the ignition coil pack. However, since both sparkplugs I checked seemed to me to be a hit carbon fouled, could it be a larger air/file mixture issue? Input is greatly appreciated!

My plan is to replace one or all of the coil packs (Bosch from FCP) and Put in a new set of spark plugs (Volvo, from FCP). The sparkplugs are 4 months old but they're 'double-platinum' from AutoZone, so I figure I'll just put Volvo in to be done with it.

Ps. These photos are both of the 3rd spark plug, but I checked cylinder 2 and it looked to be about the same.

[abscate]

Individual cylinder misfires on Volvo’s

97.3% Ignition (spark plugs, wires, coil(s), distributor cap, rotor)

0.6% fuel injection

2.05% valves, rings other mechanical

[Clemens]

Individual cylinder misfires on Volvo’s

97.3% Ignition (spark plugs, wires, coil(s), distributor cap, rotor)

0.6% fuel injection

2.05% valves, rings other mechanical

... and Steve did scientific research on this for 12.4 years, so these numbers are accurate.

[smacknab]

Turns out I had 3 original coil packs on the car, each 20 years old. I swapped all five and out in Volvo spark plugs while I was there. Car is running fine again and no codes yet!

[850 LPT]

Glad you figured this out. These cars really run best on OEM spark plugs.

...and premium fuel.

[smacknab]

Glad you figured this out. These cars really run best on OEM spark plugs.

...and premium fuel.

Thanks man! I put in new spark plugs when I bought it but I didn't know what I was doing at that point.

For fuel I've been running 89, is the difference between 89 and premium significant?

[abscate]

Glad you figured this out. These cars really run best on OEM spark plugs.

...and premium fuel.

Thanks man! I put in new spark plugs when I bought it but I didn't know what I was doing at that point.

For fuel I've been running 89, is the difference between 89 and premium significant?

Not for town driving. Do try to get the revs up at 4000 once in a while to spin the valves on their seats, or loan your car to June for a week.

[abscate]

Here is a clip from my favorite Omaha Volvo owner about running his P80 for 8000 miles on 4 cylinders.

Unread post by cn90 » 05 Feb 2020, 23:36

My 1998 S70 GLT burned valve #3 at around 180K miles (this was in 2018).
I unplugged the wiring connector to fuel injector #3.
At idle, car was vibrating a bit but at highway speed, it is hardly noticeable.

Then the trans lost reverse at 188K miles, that was when I ditched the car.

So, yes, unplug #3 and turn that into a "grocery getter"...
2004 V70 2.5T 100K+
2005 XC90 2.5T 110K+