Hello all. I'm fairly new to the Brickboard so feel free to boom me if this has been anwered before:

'00 S70 AWD, 121k, US market, 4Spd Auto Trans. Recent work: New evaporator, new camshaft valve (emissions), New coolant expansion tank (old one was leaking). 105k service was performed 1 year ago.

Driving the other day and the car suddenly started running roughly. Check Engine light (steady, no flashing) came on shortly thereafter. Drivablilty extremely poor. Idle slightly rough, but doesn't stall. Runs more smoothly at cruise speed/constant throttle above 40mph, but has a hell of a time getting there. Exhaust odor is altered, bit of unburned fuel vapor, I think.

Took the car to AutoZone for a code read on the OBDII and it had a single P0305 (misfire on cylinder 5, if I understand correctly) code. I immediately suspected the #5 coil. Procured new coil, installed. Checked the associated plug and found normal-looking deposits, no damage. No improvement. Decided to systematically disconnect each coil and start in an attempt to diagnose the bad cylinder. All seemed pretty much the same, but ran best with #1 (assuming, as I was, that #1 is closest to the cam gears) disconnected. Baffled still. I'm starting to wonder if VADIS would show different information on the code.

Disconnected battery for a bit, which cleared the Check Engine light, but the car ran the same. Check Engine has so far not re-illuminated. Cleaned the MAF sensor. Same.

Haven't checked all the plugs yet, but will do that tomorrow-- althought a sudden onset of the condition would seem to rule out plug issues, wouldn't it?

I'm fairy baffled here. Trying to avoid a dealer trip if I can. Anyone have similar issues or any ideas?

Thanks!

Had a similar problem on mine and it was the CANISTER PURGE (CP) VALVE will stay always open so engine runs rich, just plug the vacumm hoses to check
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1996 964 160K, 2000 S70 60K

Hmmm. Something I never thought of. Mine actually turned out to indeed be the coil (long diagnostic and alot of trial and error, but got it running beautifully.) If the issue reccurs I'll definitely remember to check this item as well.

Thanks!
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I luv me bricks!

I have no advice to give but did want to wish a fellow flying scot man good luck!

Wade

FC #3639

Well... Got it running. Sort of a saga associated, though.

As stated previously, got the new coil, installed it, problem persisted. Checked the #5 plug and it looked normal. Unplugged each coil in succession and checked with engine running in an attempt to identify a bad cylinder. It seemed to run best with the #1 coil unplugged. Installed "old" #5 coil at #1 cylinder. Reconnected everything. Again. (Gets annoying, all this disconnecting/reconnecting). No improvement. I gave up for the night at that point and had a couple of drinks.

Today I performed the following:

-- Pulled all coils and plugs one at a time and examined prior to running the engine. All looked normal.

-- Re-installed plugs, coils, intercooler plumbing, and re-started. No improvement.

-- Immediately disconnected everything again (Aaarrgh! But I'm getting very good at doing this quickly by now.), and checked all plugs for condition. #1 was now slightly "wet" with a bit more fuel odor than the others. Hmmm.

-- Decided to get tricky and moved "old" #3 coil to the #1 position. Re-installed "old" #1 coil in #3 position (stay with me, here).

-- Disonnected battery yet again. Let sit for several minutes. After re-connecting, and prior to starting, went through service-light-reset proceedure (using trip odometer-- and no, I have no idea whether it actually works on the S70 or not, but by this time I was willing to try any damned thing) on a whim even though service light was never on during the whole episode.

-- Reconnected everything. Again. Engine started and ran normally. Drove for a bit and all seems well. Knock wood.

-- Basically what it boils down to is still replacing the old #5 coil with a new one, and powering down and restarting the electrics several times.

What I don't at all get is why the car still ran poorly after the simple first coil replacement. I'm sure there are those who are infinitely more versed on the nuances of Volvo on-board-diagnostics and ECU's than I.

Does the car remain in some sort of "limp-home mode" if an ignition fault is detected even after the original issue has been mechanically corrected? Note that there were several complete power-downs and restarts during all these antics, so I'd think that the system would revert to it's normal mode on power-up.

At any rate, it works and I'm going with it for now. If anyone can shed light on what's actually happened here, I'm all ears!
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3 Volvos: '96 S90: 70k, '00 S70: 120K, '90 740: 131K
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I luv me bricks!

Very strange. Usually it is coil #3 that goes first, not #5. You could have a dirty wire going to the #5 injector, but that does not make sense if the plug is not wet. Unless the injector is clogged.
You need to pull all of the plugs and see which one is fouled. #1 cylinder is on the passenger side/ front of engine.

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)