98 S70 all cylinders misfiring, rough idle

rgcustom · Post by **rgcustom** » 30 Dec 2012, 17:38

So I purchase my S70 for $800 broken. It wouldn't start when I bought it. Turns out it was a timing issue. Re-aligned the timing, changed the plugs for Denso platinum, Denso wires, Bosch cap and rotor, it started right up.

It drove great for about two months, until l decided to see what it could do. Gave it a lot of gas, accelerated beautifully, stopped at Mcdonalds for lunch, started it back up and though it was going to stall out and never run again. CEL started flashing.

Caled my dad, ran an OBD-II, p0302, 304, 300, 410.

During our tinkering to fix the issue, the cat got red hot. We ran to Wal-Mart to get new plugs, switched to Autolight copper. After about 20 minutes of it still misfiring, it suddenly stopped an smoothed out. Two days later we replaced the right rear cam seal due to an already exsisting oil leak we found.

The car remains drivable, however all cylinders are misfiring now. This only happens after the car is warmed up.

I feel a major loss of power, the cam seal behind the distributor is now leaking, it surges whenever i come to a stop, and so far have found no vacuum leaks.

Either it is:
a: a temp sensor
b: the plugs and wires
c: the iac valve or tps
d: a burn valve
e: vacuum leak
d: O2 sensor

I did not replace the coil and i just cleaned my MAF.

CURENT CODES: P0300,301,302,303,304,305,410

Post by **jblackburn** » 30 Dec 2012, 18:44

I'm gonna say either a cam sensor fouled by the oil leak or a bad mass airflow sensor. Unplug the mass airflow sensor and see if it will run.

rgcustom · Post by **rgcustom** » 30 Dec 2012, 19:09

Yea, it still runs

Post by **BEJinFbk** » 30 Dec 2012, 19:27

If you're blowing out cam seals,
you might want to research PCV repair.
Anything blowing out of the oil dip tube?

rgcustom · Post by **rgcustom** » 30 Dec 2012, 19:40

No nothing coming out of my dip tube, however my oil looks gunky at the tip of the dipstick. A light brown tannish color

Post by **rspi** » 30 Dec 2012, 19:54

You may have a bad head gasket. Drain a little of the oil out to make sure it's blackish.

There is also a good chance that you have a bad coil or that your fuel pump isn't delivering proper fuel pressure. Have you changed the fuel filter or checked fuel pressure?

Post by **tom39** » 31 Dec 2012, 10:21

rgcustom,

I have a 98 S70 also and from my experience these motors do not like anything but straight old school copper plugs. I also was a victim of the platinum hype and excellent marketing of the manufacture wasted my money and tried the Denso Platinum plugs and had the same result as you. I would suggest that you try another set of copper plugs. I see you already swapped out the platinum plugs for a new set of copper ones but I would try it again. I think you fouled the new copper plugs you just put in. For what it's worth, I use only VOLO OEM, they may be $55/set but I have never had an issue and the bottom line is that they work. I have seen that others on the forum have had success with the NAPA copper plugs and they may want to attest to them but I have not tried them. Online the NAPA copper plugs are under $2 ea.
As for the CAT getting hot, If the plugs were not firing you may have been exhausting raw unburnt fuel out the exhaust and it was then being burnt off in the CAT causing it to get excessively hot.
Also, I would look to see if you have a bad coil that is grounding itself to the body. When it is dark or in a garage with the lights out and the door shut, do you see any arcing to the body from the coil?

Well that's my 2-cents, hope it helps and good luck.

TOM G

JeffersV70 · Post by **JeffersV70** » 31 Dec 2012, 12:42

I had a bad rear intake cam seal on my 1998 V70, and it will cause a misfire. When the car warms up, look under the plastic cover on the idle air control/throttle cable and look for the weep hole on the bottom of the distributor cap. If you see oil leaking, that's part of the problem. When I pulled my cap you could see where the rotor would fling the oil on the inside of the cap. $5 seal from Napa, and a quick check with a balloon at the oil dipstick for pressure and I was back in business.

rgcustom · Post by **rgcustom** » 09 Jan 2013, 09:31

Replacing plugs with volvo oem, new fuel filter, water pump, seals(cam), coil, and oil change. Is there a way to clean the PCV system without completely having to replace it? Thanks for your help and support. Edit** new timing belt also.

Post by **jblackburn** » 09 Jan 2013, 10:11

Make sure to clean out the cam sensor when you remove it. Start small, see if you can fix it before you dive into the timing belt and PCV system. Plugs, maybe coil, and cam sensor would be my start.

PCV system needs to be completely replaced. You can probably re-use the oil separator box, but that's it.

Do NOT use URO parts on the PCV system. Make sure they're genuine Volvo parts.