I just recently picked up a 1998 S70 as a daily driver. Decided that 90 miles a day at 13 MPG in my lifted jeep wasn't cutting it anymore.

I've had to do a little work to it (and still have more to go) but I've done enough that it's safe for the road now, and I've driven it to work the last 3 days. Still have to pass emissions though, and get it ready for winter. But it seems very easy to work on - not what I expected!

1. Supposedly I have a random misfire. The car runs and drives great! No sputtering, backfiring, hesitation, or anything. Has plenty of power. But I have reset the check engine light 3 times, and it keeps coming back with P0300 through P0305. The previous owner replaced all the plugs and wires, cap and rotor, and fuel filter. Where else should I start looking? Any common places for vaccuum leaks on these cars? I also have two DTC's for the O2 sensor bank 1 sensor 2. Could it be related?

2. It seems very low-geared for highway driving. At 70 MPH, I'm around 2800 RPM, but has plenty of power. Is this normal? It still beats my jeep which struggles to go 70! Just seems like I could be getting better gas mileage if I could keep the RPM's down. Is there an overdrive button I'm missing somewhere?

3. The ABS and TCS OFF lights are on. I'm guessing a wheel speed sensor on the knuckle? Is there a way to test these (ie. an ohm test?) to determine which one is bad, or do I need someone with a special tool?

Thanks for the help. I'm looking forward to saving $45 a week on gas with this car! And it's nice to still be comfortable and be able to keep my man-card! lol.

 

A couple updates...

Did the O2 sensor yesterday. Those codes went away, but the misfire is still there.

Regarding the misfire - it seems to only trigger the light when the car is warmed up. It was a cold morning this morning and I drove it 30 miles before the light came on. But if I've been driving, and I stop and clear the light, it'll come back on a mile or so down the road.

 

I'd be keen to know the answer to your P0300 error. As I too have the same error code and the car seems to run fine. It idle's smoothly, does not backfire and/or blow smoke. The only difference is, my V70 (non turbo) comes with coil packs.

I'm also getting P0135 and P0136 errors which points to both O2 sensors. Replacements are on the way. But keen to know how to fix the P0300 error.

 

Not only do I have P0300, but also P0301, P0302, P0303, P0304, and P0305 (individual codes for each cylinder misfiring). If I check it immediately after the light comes on, the only ones are P0300, P0302, and P0305 (random, 2, and 5) but if I keep driving, all the codes will trigger.

The only ignition component that hasn't been replaced is the coil, and the local junkyard has one for $25. Think I'll give that a shot tomorrow. I would go new but the auto parts stores are out of my budget, and I don't have time to wait for one to be shipped from an online store.

 

1. What kind of plugs (brand) and what kind of plug wires? Only use OEM on the latter; aftermkt sets will give you problems. Plugs also finicky; make sure they're gapped at 0.028"; no more!
2. Normal rpm at cruise; did you ck the redline? you got plenty of headroom.
3. This is one of the years that had the "broken solder joints in ABS module" syndrome. You can fix DIY or have the module rebuilt. Not guarranteeing that the issue but ...

You didn't say if this was the N/A, GLT, or T5?

 

Replaced all my spark plugs (5x) today. And while at it I did a quick squirt of compressed air on all the ignition coils to clean and dust then a bit.

The previous plugs definitely required some changing. The central electrode was nearly gone. No wonder I was getting the P0300 error. Makes me wonder if the previous owner ever got the car serviced (it didn't come with a service history and the "Service" light was on when I got it a month ago.

Prior to the change, I was also getting the P0135, P0135P, P0136P (I think the P means "pending"), P1021, P1026 & P1028 errors

Since changing the plugs and dusting the ignition coils, all the error codes have dissappeared except for P0135 and P0135P. So I'm happy with that.

So it seems, I only need one O2 Sensor - 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) or O2 Sensor Heater Circuit Bank 1 Sensor 1

Does anyone know if this is the front or rear O2 Sensor?

 

Plugs are Bosch Platinums. Havent checked the gap. The wires are not OEM.

The car is the naturally aspirated model.

I understand 2800 RPM is nowhere near redline, but still seems high. I've driven Pontiac GTP's most of my driving-life, and 70 MPH would be around 2000 RPM, also with a 6000 RPM redline. Granted the GTP has a lot more power than the Volvo and different gearing. I understand it's like comparing apples to oranges, but that's what I'm used to.

Can I test this module? Rather not go replacing/repairing something if it's not broken in the first place! Again with the Pontiacs and my Jeep, you can test most any electrical part with a multimeter to determine if it's good or bad. Not sure if this car is the same, or what the test criteria would be?

 

My 70 MPH cruise is about 2,650 I believe. On my 850 it's about 2,850.

My sig has info about ABS lights.

Most spark plug wires have a date stamped on them, week/year. Check the date.

I would do a compression test to check what you have there. Also, plug wires like GDog said really should be OEM brand (or Bungi - which I think are OEM). The coil may be bad.

 

Correction, my RPM's are 2480 in my 850 at 70 mph. About 2280 in our S70.

When I hit the gas my car kinda shifts out of some sort of OD and the RPM's are about 3,000 while accelerating. When I cruise it comes back down to 2,480. When I drop it down to 3rd on the shifter, the RPM's go up to 3,500.

 

I'll have to ck my rpm @ 70 again and get back to you; my 850 is also N/A.

Ck the gap on your plugs; that may be what's causing the misfires if they're a bit too wide.

Never seen a control module you could test statically with just a VOM. Doesn't matter who makes it. It's an embedded computer; have to test it dynamically. That's why they have break-out boxes for doing that. Even static VOM tests on things like ignition coils aren't conclusive.

With regards to your ABS issue, first step is to read any codes that are set.

 

I replaced the coil yesterday. No misfire codes yet! But now I have a new one... P0410 secondary air injection system malfunction. It doesn't set off the light, just a pending code. I never had it before. So once again I'm stumped! And have 3 days to get it inspected!

 

I have heard that some areas will pass with that one.

 

NH will not. Here, we can't have any check engine DTC's.

Something interesting though... I did a little googling and found that 9 times out of 10, P0410 is caused by a vaccuum leak. So I retraced my steps...

I found that when I removed the airbox to replace the coil, I accidently disconnected the vaccuum line that runs the valve to switch from the normal intake to the "hot air" intake. You guys probably have technical names for them... that's just what I call them. lol.

So that's where my P0410 was coming from. All the time I drove around with that line disconnected (and P0410), I never got a misfire code. When I plugged that line back in, P0410 went away, and my misfires came back.

This is getting super confusing. My only theory is where that vacuum line runs to the valve to switch intakes, that the valve is only opening part way, and the engine is starving for air. With the line disconnected, the valve would stay fully closed to one side, so the other intake was still fully functional. But again I know nothing about this intake system, and the car seems to run fine and have plenty of power. But that also makes sense that it would only trigger the code when the car has warmed up.

Update: I reset the codes when I left work. By the time I got to the shop they were back up as a Pending codes. But I guess pending codes don't count on the test, because I passed! So now the car is inspected until next September, I'm not in such a rush to straighten this out. Although it would be nice.

 

Phew, that was close. I'm not sure why you are getting the misfire codes. Does it choak when you are reving over 3k? With the car moving.

 

I haven't been over 3k very much. Been trying to keep the revs down for MPG's. It's not like my jeep where you have to hold it to the carpets to get it to move! But I've never had any noticeble issues. I'll push it a little harder on the way to work tomorrow morning and let you know.

Speaking of MPG, my last two fill-ups have been 23.3 and 23.4 MPG. Is this what I should expect? My commute is mostly a steady drive 40-55 MPH with only a couple stop signs. Could the misfire be bringing it down? Regardless, it's much better than what my jeep was getting!

 

It's hard to say, really depends on how far you drive. The first few miles, while it's warming up you'll usually get about 17 mpg, once warm it should get around 30 mpg between that speed. So if you're driving 10 miles or less, that would be great. If you're driving 20 miles it should be much better, like 27+.

It's kinda of a big deal to use OEM Volvo plugs with these cars if you want the best gas mileage. You'll pay $20 for some good Bosch plugs and $45 for Volvo plugs but the loss of gas mileage will cost you the difference in those plugs in 2 tanks of gas, like 700 miles of driving (about a month). Then when you think you'll keep those plugs for 30,000 miles, wow what a deal. 30,000 miles by 23 mpg = 1,304 gallons. @ $3.75 per gallon, that's $4,891. If those plugs are costing you 10% in gas mileage (get 25.3), that will be 1,185 gallons, which would cost $4,446. A difference of $440. So, Volvo plugs would save you about $415 over the long haul.

The same situation goes for 91+ octane. A lot of people will pump the 87 @ 3.49 instead of the 91+ @ 3.82. That is about 9.5%. Some people have found that they can get 2 mpg (some as much as 3) better gas mileage with 91+ which at 3 mpg is better than 10%. Which means it may be cheaper in the long run to pay for the 91+ gas than running the 87 octane. The owners manual recommends 91+ so it's better for the motor. Running 87 can cause issues with the motor if the knock sensors fail to operate properly. Lower octane gas will cause the car's computer to retard the timing to prevent kock, etc.

Check it out for yourself. In one of my 850's I was getting 25/29 and 24/30 in my 960. Most people get 21/26 in their 850's and 19/23 in their 960's. So I was getting about 20% better mileage than most. I just replaced the plugs in my wagon and mileage has gone up a little but not as much as I'd like. I think driving around with all the tools that I have it eating me up a little.

I will say this, I tested my mileage on long road trips, where you fill up and drive down the freeway at 70 mph all day, dumping a tank of gas in 6-1/2 hours... I tried all kinds of gas grades, types, ethonol free, etc. Went from $3.49 per gallon to $4.35 per gallon and seen NO difference in mileage. So, when I hit the road to go 400+ miles I now pump the low octane stuff. When cruising down the highway at 70 mph you are only using about 50 hp. Up most hills (not grades, hills) about 85 hp so it really doesn't make any difference. I just don't get into it if I have 87 octane in it, don't want to risk knock. But around town or if I'll be passing in the mountains, I always go with 91+ octane.

 

Wishing I lived in Arkansas right now... "warming up" means different things to you and me. This morning it was 27 degrees out when I left for work. I can either let the car idle for 20 minutes before I leave, or have it get up to temp just as I'm getting into town. I usually do the latter. Also 87 octane being $3.49/gal. Its $3.85 here (I know some areas have it much worse). It goes up 10c for every 2 octane "points". Our premium is 93 @ about $4.19/gal. I'm familiar with Knock Retard and the need to run high octane fuel on forced induction engines. My GTP didn't even like 93 octane... still got 5deg of KR! That is until I upgraded the intake and tune. But is there anything special about the naturaly aspirated S70 that warrants running a higher octane? Or just that it burns cleaner/more efficiently? So it seems 27mpg or so may be attainable during warmer months.

 

It is not good to start a car and let it idle to warm up. The car motor will warm up a lot faster with a driving load on it. You should not push it until it's warm.

The NA motors are built at a higher compression ratio, 10.0:1 while the turbo models are 8.5:1. My understanding is that 9.0:1 calls for higher octane. The reason they recommend it on the turbo cars is due to the rate at which the turbo can cause a real fast rise in rpm's.

Ouch on your gas prices. It looks like 20c to every grade up-grade.

 

I've heard it both ways on how to warm up your car. I prefer to do it the way you reccomend. I've always just figured it saves gas.


I was unaware that the compression ratio was so high on these motors. The GTP also has an 8.5:1, but the supercharger also increases that (as would a turbo on the T5/GLT). It basically compresses and forces more air into the motor, and with compression comes heat. Lower octane gas can ignite prematurely (predetonation / knock) so that's why higher octane is required. That's how I understand it, though the quick rise in RPM's makes sense too.

Next fill-up I'll try a different octane and see if I notice a difference.

 

The Volvo manual recommends driving the car to warm it up. The winter before last I did a test. It takes about 3 miles in 40 degree weather to warm a car up and it took about 15 minutes to get to the same temp letting it idle.
1998 S70 & V70

The deal is, a cold engine wears faster than a warm one does. Running rich and whatever else causes it to run while cold.

Correction on the compression ratios:
NA = 10.5:1
LPT = 9.0:1
HPT = 8.5:1
1998 S70 & V70