P0305 Code (misfire code) Topic is solved

adbalt · Post by **adbalt** » 08 Jan 2016, 08:37

98 Volvo S70 GLT. Code reader throws a P0305 code. Car drives fine but gets a little rough when you slow to a stop. Any ideas on what causes this code? Recently replaced the MAF and that code cleared and it does run a little better. Thanks

Post by **abscate** » 08 Jan 2016, 09:14

Lift the plastic lid (tor bolts) and look in the spark plug holes for oil and water. Then pull plug and insspect. Get ready to test compression in #3 cylinder too.

When were plugs rotor cap and wires last replaced??

On edit..misread code, cylinder # 5 potential problem

adbalt · Post by **adbalt** » 08 Jan 2016, 09:26

I got the car with 250,000+ miles on it and it was neglected. I've been using it to learn on as I have never been mechanically inclined. I recntly changed the PCV, and the MAF but still runs a bit rough at slow/stop. I have no idea when the plugs and wires were changed bu they do not look stock. Probably a stupid question but how do you test compression? Thanks

Herb Goltz · Post by **Herb Goltz** » 08 Jan 2016, 09:30

P0305 is a misfire on cylinder 5 (closest to the transmission). Plug, wire and distributor cap are all suspects-- if they are ruled out, then a compression test is in order.

Good luck!

adbalt · Post by **adbalt** » 08 Jan 2016, 09:33

Cool Thanks for your help

Post by **erikv11** » 08 Jan 2016, 10:11

You check compression with a gauge, you can "rent" one for free at Autozone etc.

http://www.popularmechanics.com/cars/ho ... -14912158/

Some key points:
- engine must be warm
- throttle should be wide open, floor the pedal while you crank it
- I also pull the fuel pump fuse and unplug the coil wire
- crank it until the gauge stops climbing, usually like 5-8 cycles of the engine

obayha · Post by **obayha** » 08 Jan 2016, 10:27

I pulled cap and wires from my '98 before in got scrapped. They are not very old and are yours for the shipping, if you want to try and get out cheap on a fix. Mine was a '98 V70 T5, so I think they would work on yours.
Do a compression check. I usually pull all plugs and turn off fuel pump.
Two people work best on some things.
Shane

Post by **FLXC90** » 08 Jan 2016, 13:50

Welcome to MVS-you'll find all the information you need here. Since this is a practice car, and not your daily driver, take the time and fix things right. Shane's offer sounds like a great way to get started-cheap. Read the threads on Stage zero-ing your car. I bought my 98 S70 (225k miles) for $300 two years ago, put about $600 in it in parts, including initial fluid changes, and that's been it. It still needs some things, but it starts every day on the first try, and is drop-dead reliable.

As mentioned, your 0305 code says your #5 cylinder is misfiring. pull the plug and check it, also pull the distributor cap and check the contacts, you might be able to clean them and get by until you replace them.

When you pull the distributor cap, look for oil leaking behind the rotor, common for the seal to come loose, cheap easy fix, but leads to next task, check PCV. Look at threads or RSPI's youtube videos on glove test and PCV cleaning and repair.

adbalt · Post by **adbalt** » 09 Jan 2016, 17:07

Thanks Oba and FLX. I just checked the plugs and pulled the wires while it was running and 2 of the wires did not arc so I take it that means wires are bad for starters. Also one of the plug wells had a lot of oil in it. I'm sure that cannot be good. What would that be a sign of? and how difficult a fix? Starting to think it may be a bit more than I can do.

Thanks

Post by **erikv11** » 09 Jan 2016, 19:18

The oil in the plug hole(s) could be minor, the most common cause of that is a leaky PCV hose, the one that connects under the plastic plug wire cover. Is there a fair bit of oil up there, on the cam cover? Also, a leaky oil can cap lead to the same thing.