1997 850 Codes p0300, 0303 and 0304

Post by **m491** » 07 Jul 2015, 12:04

My son's 850 threw codes p0300, 0303 and 0304 at the same time 3 days ago. I asked if it misfired or ran rough he said no. I drove it and found no performance issues. I checked under the hood and looked to see if the distributor cap had any visible cracks etc and none were found. I didn't take it off so there may be an issue underneath where you can't see without removal. The spark wires do not date stamps so the previous owner must have replaced them with non OEM at some point. The car has about 110k miles and if the plug wires were changed out it was at least 40k miles ago. The coil looks original to the car.

So I cleared the code and wanted to see if it came back immediately. After 3 days of very light driving (less than 50 miles) the codes have not come back.

So my question is before I place a order for plugs, wires, diet cap and rotor with FCP is there something else I can check before replacing parts? The coil went bad on my older son's 850 and that car would not start until I replaced it. So I'm not sure what type of random could issues could cause a CEL to come on and still run. Again, I don't want to chase something by throwing parts at the issue until something works. The car could use a tune up but we had planned on doing the evaporator one of these weekends and I just had to do control arms and an axle boot so I don't want to do an unnecessary tuneup at this time.

Thanks in advance for any good ideas of what to check.

Post by **erikv11** » 07 Jul 2015, 13:40

I would definitely pull the distributor cap and look inside it for oil and/or moisture residue. The initial report is multiple misfires, a common cause of that is when a rear cam seal blows out, usually due to clogged PCV.

Post by **m491** » 08 Jul 2015, 05:45

The PVC is fresh and only has about 12,000 since it was done two years ago. Maybe cam seal could be the cause and I hadn't seen that in other posts. Thanks for the suggestion. Right now the code is gone but I'll get a new cap and rotor and see if there is anything dripping up near the seal.

I'll check back in when I get my parts delivered.

Post by **erikv11** » 08 Jul 2015, 08:23

If the cap and rotor are coming anyway, then when you get in there I would even pull that metal plate the rotor mounts on, it is only one 10 mm bolt, just to get a good look at the cam seal and be sure. But with recent PCV service the cam seal may be a longshot. It is common for the codes to show when they blow but not necessarily afterwards.