Mikeythrash

now I just got codes P0300,P0301,P0302,P0303,P0304,P0305,P0306.Multiple misfires all cylinders! before anyone asks 3 months ago it got new wires ,ignition cool,spark plugs "champion", CPS sensor new hoses new radiator and a ton more and not to mention new head gasket head was machined and all new seals etc...Where do I start? And all those codes really say are misfiring not what's causing it to misfire.So yeah troubleshooting I assume but where do I start.Or should I take it to a dealership and have them make it pur

tjwalker

You have one "common" problem causing all cylinders to misfire.

The first thing I do with this type of problem is to verify fuel pressure. I will guarantee you that any technician worth their salt will do the same.

Many parts stores will rent you a fuel pressure gauge inexpensively. I believe the fuel pressure spec for the 96 is 49 psi, plus or minus 5 psi......but some early 96 may have the old fuel system where the spec is 31 psi. So you need to determine that.

Start there. Let us know what you find. Good luck!

Mikeythrash

I need to do this sooon now when I idle especially come up to a light or a stop it putts real rough and sounds like it's gonna stall but it doesn't.

sycoglitch

Would be hood to know what you're driving. Is this on your prius .

And what brand CPS did you install

Mikeythrash

CPS was an Airtex and fuel pressure was at 40 psi

sycoglitch

Get a mopar CPS. AIRTEX leaves people stranded

Lowrange2

Assuming we're working on a 1996 Jeep Cherokee I'd start with checking out the rotor button and cap visually, test the coil and cps. Betcha it's one of those.

Lowrange2

Yup, though, I've never had a CPS cause a random multiple misfire but I wouldn't put it past it.

Mikeythrash

And it's a 96 XJ county 100,700 miles has new head gasket head was machines new hoses ,plugs.wires all that

sycoglitch

I agree the symptoms don't match but at least it'll save future issues.

Lowrange2

Start with the "plugs.wires all that". New box store parts are just as prone to fail as 15 year old OEM parts.

Pull the cap and check the rotor button.

Mikeythrash

Yeah this weekend I am just gonna get a new cab and rotor wires plugs putting new injectors on upgrading the manifold and ordering a new IAC now after I do all that and if it is still doing the same thing I will go to the CPS. As far as fuel pressure it's at 40 PSI is that good someone said fuel pressure spec for the 96 is 49 I believe I have a later 96 it has the over head console and all don't think earlier ones have that.

Mikeythrash

Btw you know all 6 cylinders are reading multiple misfires.

Lowrange2

Don't do all that until you figure out the cause of the issue. Adding multiple parts at once just complicates things. Just pull the cap off and look at it. Take a picture of it. Post it.

If the cap and rotor look good then test the coil and cps. Don't just blindly replace it.

40psi is acceptable.

Yes. That's why I suggested looking at those parts.

Mikeythrash

I have a pic it's not letting me upload it