Misfire issues?

marcusmcd · Post by **marcusmcd** » 03 Jun 2021, 13:00

96 850 SW is blowing smoke and running rough. On recommendation, I replaced the catalytic converter, but no change. Took it to an auto parts store to read the codes. Got:
P1310 No DCTC definition
P0303 Cylinder 3 misfire
P0305 Cylinder 5 misfire
P0300 multiple misfire
Spark plugs are good. Any suggestions as to what I might check and/or fix?

Post by **misha** » 03 Jun 2021, 14:19

What color is the smoke...black or blue?

Post by **abscate** » 03 Jun 2021, 14:21

Move the coils around to see if the misfire codes change. Probably, you need two new ones

Post by **volvolugnut** » 03 Jun 2021, 15:47

Is this engine coil on plug or distributor ignition system? For coil on plug type check coil grounds and swap around coils to find bad coil. For distributor type, check condition of coil wires and distributor cap.
volvolugnut

Post by **rguzz** » 03 Jun 2021, 18:41

Compression test soon, if not next. Did this come on abruptly?

Post by **seggs** » 03 Jun 2021, 20:42

Sounds eerily similar to a problem I had with my 04 xc70 a few months ago. In my case it ended up being a burnt valve. If you going to be switching around the ignition modules anyway, your just 5 spark plug removals away from doing a compression test. You can get a usable on for about $25 on Amazon. Then you at least know it’s not that. I could have saved the cost of 2 modules if I would have done a compression test. Also, check out the wiring to the modules. Mine had large amounts of the wire insulation dried & flaking, which I had to re-wrap.

Post by **scot850** » 03 Jun 2021, 22:04

Coil packs on plugs did not come into use until 1999 models. Car will be a distributor with plug wires to the plugs.

Check the plug condition. Also remove the distributor cap and check for damage/wear to distributor cap and rotor. Also look for oil in the base of the distributor.

Turbo or NA?

Check there is not oil running into the top of the engine from a blocked PCV system.

Also check the plug wires have not been trapped under the cover near the distributor. They can get picked and short out.

Let's try the simple stuff first before we panic about the compressions.

Neil.

Post by **erikv11** » 04 Jun 2021, 01:12

What Neil said, start there, especially this:

scot850 wrote: ↑03 Jun 2021, 22:04 ... Also remove the distributor cap and check for damage/wear to distributor cap and rotor. Also look for oil in the base of the distributor.

but all of what Neil said.

Post by **rguzz** » 04 Jun 2021, 06:40

I see it a little differently as a compression test is easy, quick and reassuring if the numbers are in spec. If they aren't, well then you have your findings to deal with. It's kind of a make or break point in your diagnostic algorithm, and takes less time than a tune up. When my compression numbers are normal, I can then relax and take my time as I move on. Basically, it's the biggest bang for the buck, if you will. No parts to buy other than finding a tester.

Post by **scot850** » 04 Jun 2021, 14:50

Agreed. Compression test is a good thing to do also. Can be done as part of the checking the spark plug process as the plugs are out anyway.

Neil.