I finished the new head gasket and took it for a road test. It threw a p0302 code, so I was checking the plugs, I noticed I had the 2 and 3 spark plug wires in the wrong place on the coil packs, so I put them in the correct place, and erased the code with my scanner. Took it for another road test and it felt fine but then it threw the same code again. Im not sure why??? Any help please. Thank you
Ps. Its a 1996 sl2 Dohc. With under 100,000

 

The misfire did not move with the plug wire, so the plug wire is unlikely the cause. Maybe a defective plug? If the coil pack was an issue I would expect the issue to move to #3 or to have both 2 and 3 having issues... since they share the same coil pack.

I'd pull the plug in # 2 and inspect -- check the gap -- and also see if it is fouled.

I'd also check compression on all 4 cyls to be sure the head gasket is intact.

 

I figured out one of the valves is leaking oil into the number 2 cylinder,and making it misfire. I could here the valve ticking. I went and got some MMO and put it in the oil, the valve got a lot quieter. At first the light would come on in about five minutes. After i added the MMO it took about 30 minutes of me driving to make the light turn on. I was trying to get it smoged and as soon as i got there the light kicked on. I pulled the plug and there was a thin layer of oil on the piston. If i erase the p0302 code will it smog? Any help please. Thank you

 

The light is still coming on now but after letting the car fun for about an hour it now takes around an hour for the light to come on but it still does come on and it is throwing the same code. Valve seals???

 

How is compression in #2? If compression is OK, it could also be valve guide seals which are known to seep oil. If you choose to rebuild the head be sure to do the valve guide seals as part of the job.

As for passing smog -- the issue you may run into is the following:

When you clear the code, the "status" of many of the diagnostic categories for the subsystems of the engine management are set to NOT READY. Part of the inspection check in most states involves ensuring the SES/MIL light is not on, there are no ODBII codes stored (hard codes or pending codes), and that the majority of the diag categories are in the "ready" state, meaning that the PCM has collected enough data on each subsystem to determine that the particular subsystem is operating correctly - or isn't.

Many systems will become ready within very few drive cycles but things like catalyst efficiency (cat converter) take a bit longer as more data must be collected before the PCM decides whether the cat conv is operating properly. So this diag will be in the "not ready state" until you go through enough drive cycles.

The upshot is that if you clear the codes while sitting in line at the inspection station, you will likely fail inspection for having too many "not ready" flags set -- even if your SES is not on and you are not throwing any codes (I've been there as I had failed emissions, then performed a repair and cleared the codes, but did not have enough drive cycles completed.)

The misfire codes are nasty because they will set pending codes very quickly (in my experience) before the hard code sets. The only way to know your ready/not ready flag status is to experiment with a code scanner that can also give you this I/M status information.

Clear the codes, drive around, and check for codes every so often to see if you have any pending codes set. If you do, you're pretty much doomed already. If you don't have pending codes, see how long you need to drive around at various speeds to get all the I/M statuses to come up as "ready". You can then gauge whether or not you can expect success at the inspection station.

Hope this helps. Let us know how it turns out....

 

Thanks for all the help derf. My scanner has the IM setting I just didnt know what it was. I saw what you were talking about because everything showed ready but the o2 sensors. I drove it around but the SES would always come on before the IM said it was ready. The part that is frustrating is that I just put the car back together and it drives fine but it wont pass smog because of the SES. But it never showed any pending codes. Im not exactly sure what throws the code? Is it caused by oil getting on the spark? Is that what makes it misfire? If so can I run different spark plugs so it wont throw the code during smog?

 

I dont have the tools to check the compression but I do have one of those valve tools that put compressed air in the cylinder. I did the test twice because I didnt know what psi to use. I was just trying to see if i could hear the air coming out. So the first time I put 30psi into the cylinder 5 min after i let it idle for a few minutes, I had the oil fill cap off, and when i put the air in the cylinder smoke started coming out of the oil fill cap spot. It would stop as soon as i released the air. Does this mean bad valve guide seals? Next i took off the valve cover to see if i could see where it was coming from. This time I put 50psi into the cylinder and it pushed the piston down. Thank you for all your help, im just trying to get it fixed this is my only car. Thank you

 

My guess is that it is the fouling of the plug which is causing the misfire -- once it gets sufficiently oil soaked, it cannot fire properly. The ignition system can sense it , presumably based on a change in resistance, so the misfire code sets.

I'm wondering if you can

--clear the code,
--drive around and get all your other I/M to ready
then
-- pull over
--GENTLY replace the fouled plug with a new one
(gently because this is an aluminum head and you do NOT want to overtorque and damage/distort the threads when it is warm)
--drive around a bit until the SES light goes out on its own (leap of faith on my part that it will not misfire when the new plug is first put in)
--go directly to emissions testing and roll the dice

I don't know if the above is possible since I don't know how long it will take the hard code to reset without being cleared once the PCM senses the misfire is no longer present vs how long you can drive until the code sets.

I have also read somewhere that cycling the ignition fifty times in a row without starting the engine will clear codes out of memory, but I do not know if this is true or bollocks - I've never tried it personally, and I also don't know if it affects the I/M status stuff.

 

when i put compressed air into the cylinder and it came out the oil fill cap, do you think that means the valve guide and seals are bad, or would it be the rings?

 

to interpret the results of this kind of leak down testing, you need all the plugs removed and the cyl you're testing needs to be at top dead center....was this the case with your testing?

Since exhaust valve leakage can usually be heard in the tailpipe and intake leakage can be heard through the throttle body. The fact that you hear it/feel it at the oil filler cap makes me think the air is leaking around the piston -- but please remember that there will be some leakage on any cyl since they are not designed to be completely sealed...so I can't say for sure the rings are worn.

Did you ever get a chance to do the compression test ? what were the results?