Several months ago I acquired a 99 s70 GLT for a great price. It ran fine except for one problem, sometimes it would toss up the ETS light on the dash and the cruise control would stop working once the light came on. Having read up, I know this is a common problem this model can have and it is in recall by Volvo. So I brought the car to the local dealership to have the problem fixed (they applied an ECU software update, it seems to have worked) however, 3 days after having the update applied cylinder 4 went dead and so I brought it in and had the ignition coil for that cylinder replaced. Mechanic said the other coils looked okay to him and that I could save several hundred dollars just letting them be for now. While I had the car in the shop I had them replace the spark plugs and fuel filters as well as running a fuel injector cleaning.

After getting my car back it drove GREAT. Very smooth acceleration curve, engine had almost no vibration, and at idle the car was very quiet. Then, a few days later, I started getting sputtering sometimes at idle. Over the course of a week it got worse until it turned on the check engine light for misfires on cylinder 1. So I brought it back and asked for the mechanic to make sure all the plugs were gapped properly, and nothing was poorly connected, or such. I was told it was the ignition coil, so I went ahead and had the other 4 replaced. So with 5 new ignition coils I drove out that day.

Immediately I noticed that the car seemed more sluggish than it was, and the engine was idling much more loudly and with a noticable vibration, and during driving I noticed a very low moaning/whistling noise that I had never heard before. Of course by now I'm rather annoyed. I brought the car back in and asked for it to be checked out again, explaining all of the symptoms I had noticed. The mechanic wanted to drive a short distance with me, so we did. He declared the car seemed normal to him. In my frustration I went to the service manager and explained everything about what had happened over the past 2 weeks to him. He brought the car immediately back to the shop and hooked it into the volvo computer to read the service codes. It came up with some codes from the rear o2 sensor. The service manager stated they reset the codes, and he wanted me to drive it and bring it back on Friday to see what came up in the meantime. Well, fast forward to around noon today (a few hours after the volvo shop cleared the service codes), and the check engine light comes up. It's a rear o2 sensor code. I called about it, and was told I must need a new rear o2 sensor, or possibly a new catalytic converter.

I'm not buying that. Car was running great a week ago, and aside from the misfires that started coming up, was running quiet, smooth, and never was having this kind of vibration and performance issue. (not to even mention the new moaning/whistling noise I can faintly hear driving now)

I'm thinking a leak in one of the hoses was caused somehow in the latest trip in to the shop, but they seem disinterested in looking for one.

Anyone else have a similar issue come up and/or any thoughts on this one?

 

And today the ABS light came on... Quite the chain reaction. Anyone got any ideas?

 

Maybe the O2 is the cause of the running?
How long total were you driving with the misfires?

 

I have no doubt that the O2 could be the cause, or just a symptom. I ran about 3-4 days after I started noticing random misfires on cylinder 1.

 

That really should not have wiped out the O2 but it is possible.

I think it just might be Ironic that is all happens at the same time.

The ABS is seperate though the module can go bad at any moment the key is on.

 

In any case the car will go back to the shop one last time tomorrow to read the codes that have amassed in 2 days. Somehow I don't forsee satisfaction forthcoming.

 

Sadly I think I would have to agree.

 

Oh, something else I noticed, I thought this morning the exhaust from my car smelled faintly of gasoline. Probably connected to a bad O2 sensor?

 

Okay, I took the car in again this morning and they pulled the codes again, what they found was an fault on the front O2 sensor, not the rear one (not sure if I misread something before). It reads as so: ECM-280A Front heated oxygen sensor (HO2S), bank 1 - Faulty signal DTC is found active It also says 5 operation cycles since fault was last found. Does the front O2 sensor need to be replaced or am I hunting snipe? Could the front O2 sensor cause the sort of symptoms I described? (more vibration and louder idle from the engine, lower acceleration, a low moaning whistling noise, lower gas mileage)

 

Yes it can cause pretty much all those issues.

 

An interesting thing happened a few days ago. Suddenly my S70 seems to be getting less vibration and the car's power and gas mileage seem to have come back to around where I remember them being before. I haven't had anything done to the car since my last post, aside from topping off the engine coolant on the same day that the performance seemed to return. Obviously that couldn't have anything to do with it, but any ideas on what could? I haven't had a check engine light since having it serviced, and haven't had any check engine lights since it started working better again.

 

Very strange not sure.

 

I believe I have figured out the reason for this problem (came to the conclusion of the past week) and strangely, it seems someone else ran into the same problem in another thread. It seems to me that the AC compressor must have been running all the time, just going by how the car runs with the AC on vs off vs how it was running at all times over the last month before the problem cleared up. (including the differences in gas mileage - get over 25mpg without AC, around 22 with) For now it seems to have gone back to working normally. I believe that's what the problem was.