Misfire in cylinder 2 once again
 

Hey guys I get the code p0302 misfire in cylinder 2. I have new spark plugs, new wires, new injector, so im lost now. I thought it might have been the injector so i bought a new one but the code came back. I checked the spark in the spark plug and the spark is fine. So i would think the wire and distributor cap are fine, Since i do get a spark. Hmm Im thinking it could be low compression in cylinder 2 or maybe the wiring by the injectors. I looked at that and one of them seems to be pinched in. Cant tell if its cut or not. Another thing is maybe the spark plug gap is to big. Thats all I can think of, do you guys have any ideas what else it could be ? I was planning on going to UP michigan to do some off roading with a friend, hopefully i get this fixed so i can go.

Start by verifying gap on plug. .035 is the correct spec. Doubtful this is it, but it takes all of 5 minutes to inspect the plug and gap it. Swap it to another cylinder while you are at it to see if the code follows to that cylinder.

Compression test on all cylinders is never a bad idea. A good "snapshot in time" of the internal condition of the engine. The spec compression for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.

Start there....

what kind of plugs are you running? Run NGK V-power they are the best for chrysler. my jeep, dodge ram , and my durango will not run on anything but NGK's they misfire and and choke.

Start with tjwalker's suggestions... if that checks out, you can test the injector/ wiring by swapping #2 injector with one of the other 5. If it moves its the injector, stay on cylinder 2 its something else.

Bosch plugs have been linked to confirmed misfires. Although some 4.0 engine can get by with them, I don't recommend them. I generally like Bosch products, but gotta go with the data here......

For 87-99, I recommend Champion copper plugs

For 00-01, I recommend NGK copper plugs (different ignition system and NGK plugs hold their gap a bit better than Champion on this distributerless ignition)

check fuel pressure as well, should be 49 PSI I just chased this same problem, did plugs, cap, rotor, wires, o2 sensors, injectors o2 sensors seemed to get it

hey thanks guys, I just put in a new distributor cap and rotor, the other one when i took it out was pretty corroded. The rotor on top was a lil corroded and kidna burnt as well. Hope fully this will fix the problem. If not il check the spark gap, fuel pressure and do a compression test.

Also since i did unplug the battery while working on the car and it resets the check engine light. So its gone for now, in this case do i have to wait until it comes back on or if i scan it itl show me right away if something is wrong ?

and actually i do believe i might have the bosch spark plugs, maybe il change them out as well to champion copper ones :)

I change my distributor cap, rotor and plug wires every 60k. Plugs every 30k.

If you still have a misfire, swap out the Bosch plugs for Champion copper plugs.

Just drive it now and see how it runs and "if" the check engine light returns. Hopefully you found it with the old cap/rotor.

Well i changed the spark plug in cylinder 2 and either way I had champions in them previously. Just got to michigan and i remote started my car, after like 5 min of driving the check engine light came on :( Im thinking il switch the spark plug wires and if thats not it then what ? Guess i should check for low compression ?

Yes, once you've ruled out injector, spark plug, plug wire and distributor cap, that's it for peripheral things. Can't ignore a possible internal problem. Compression test is easy to perform and is a good "snapshot in time" of the internal condition of the engine.

Spec compression for the 4.0 is 120-150, with no more than a 30 psi variation between cylinders.

Good luck and keep us posted!

Have you checked out the wiring to the injector as well? mostly the bundle that runs down your manifold by your fuel rail.

My 96 was throwing a #1 cylinder misfire code, and a compression test showed 45#s in it. The valve seat was bad.

thanks guys, i have a feeling the remote starter might of messed something up. The first time i did it the engine didnt catch on. Then i just started it and after a few min the engine light came on. So i reset it and iv been driving it for a few hours and its all good. I will check tomorrow and see if it comes on. As for now im in UP michigan and if it does come on il check it out when i get home. I will probably do a compression test just to see what it reads. If it does come back on il try the spark wires and the injector wires, as well as the valve seat.

thanks for all the help guys :) I will report back after my short vacation lol.

Also i did check the injector wires and the one for cylinder 2, it seems like one of the wires is pinched, although its not cut. Im guessin that could be it as well. I'll know after I do some more tests.

A "noid light" is a nice thing to have on hand. Easy to hook up inline and it will tell you if the injector is firing or not.

I agree that is a good idea to verify that you are getting a PULSE to the injector. Swapping a new injector won't help if the injector is not receiving a pulse telling it to operate.

If no pulse in only one cylinder, suspect a wiring or connector problem specific to that injector or possibly something internal to the computer.

ahh, Ima see how much they cost, maybe il pick one up.

alright, well no check engine light today so im starting to assume that the remote starter caused the problem.

Grr, the damn light came back on. This eliminates the remote starter, distributor cap/ rotor, spark plugs, injectors. Think I will test it out for low compression and see whats up.

No need to spend money on a set of noid lights. get your self a 194 bulb bend the wire prongs down and insert it into your fuel injector pig tail and it acts the same as a noid set.

^ nice nice, I just asked auto zone they rent out a whole set for 25 bucks and then when you return it you get your money back. I might pick it up once it stops snowing. But il try what you said as well so i have one at home :)

Anyway like I mentioned before I had the spark tester plugged in the wire and into the spark plug, the flash was constant. This means that the plug is sparking but does this also mean the wire is good or could the wire still be bad ? I would think if the wire was bad I dont think Id get constant flashing. Am I right or could the wire still be messed up? I found my old spark wires so im thinking il replace the cylinder 2 wire and see how it goes, then if thats not it ill test the injector wires.

Why do you avoid the obvious? Do you like the misfire?

Check that compression!

I will check it! I dont sit on my *** everyday doing nothing. I go to work and school and I have to go to my uncles to get the compression checked since he has the tools. Like I said its snowing crazy over here, we got about 4 + in of snow and theres traffic everywhere. I also dont have a garage I can pull my car into to just do a compression test. In the spare time I was thinking i could try the old wire as I have the old set. Plus the injector wire is pinched so maybe that could be it as well.

If you cant answer the question, then dont say anything because it doesnt help ;)

Check/change your oil soon when you fix the problem. If you aren't firing at all in the cylinder and especially if it does end up being compression(possible ring problem), excessive fuel can run passed the rings and break your oil down.

Looks like you got great help here, just a thought. Check that **** injector wire! Looks funky and you have a code.

USLost, "get your self a 194 bulb bend the wire prongs down and insert it" :thumbup1: nifty! I like that. My wiring is fine and i want to try it.

Course you could swap #2 & #5 plug wires easy enough if you wanted.

Curious if you can hear or feel it missing.

:) Will check that injector wire tomorrow and today ima just try a new spark wire. To be honest I dont really feel any difference. Of course its my first car so I dont have any room to talk since I have barely any experience. It doesnt seem like it idles rough or lacks power. It starts up right away so im not sure.

Could it be the dash just displaying the check engine light? Nah that cant be it since it shows a code. Just thought of it since I do get the airbag light on and all gauges turn off every now and then lol. Ground problem.

My dad blew a whole $75 on my first car. I learned what a miss sounded like pretty fast.

I did find this;

A code P0302 may mean that one or more of the following has happened:

Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer

Possible Solutions

If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Well I just swapped the #5 wire with #2 and Il see if the code comes back since Ima drive it to work tomorrow.

spark plug = replaced
injector = replaced
distributor cap / rotor = replaced
wire = swapped

No rotten eggs smell and whats a coil pack ? Is that the distributor cap ?

A coil pack is found on a distributor less ignition system. But yea your basically right. It does the same thing as a distributor cap and rotor. Just it's computer controlled instead of mechanically controlled.

I think it was 00, and 01, actually have no distributor! Individual coils on the plugs, I think? Or I saw one on something where the wires all plugged into a like, block. :icon_confused: Where the dizzy goes there is a little goody that senses the position of the cam. Forget what that is called.

Camshaft position sensor

Alrighty guys, since i worked my dad took the jeep to my uncles and they did a compression test. 80 psi in cylinder 2 **** ! The rest were at 150psi. So now that I know its the compression whats the next step ? head gasket, valve seat ?

Need to do a leak down test and that will point you in the right direction..
http://www.carcraft.com/techarticles...r/viewall.html

Sort of is a shame they didn't put a couple oz. of oil in there and see it it shot up. Of course I don't know. Certainly does sound like it could be a valve. Great link there^. Makes me want to hook compressed air to it and listen. Anybody ever pull the 02 sensor and listen in the hole with a tube I wonder? Or maybe just another plug hole with it's exhaust valve open.