E0302
 

this started as a random misfore and turned into this p0302. i tried one by one eliminating things it could be. changed to factory delco plugs didnt help. next changed plug wires. after that i changed out coilpack. i also have new 02 sensors. any tips or ideas on where to go from here before i go to a dealer to rape me on a diagnostic? id appretiate it :) sorry title shoulda been p0302. also how would a cat cause a specific cyl to misfire? i have a new cat but dont get how that could even be a posability?

If it's not plug, wire, or coilpack, I would guess either a shot injector... or a stuck valve I would doubt the valve so check the injector first. A clogged cat could cause horrible flow causing reversion and killing your intake stroke.. of coarse im pretty drunk right now but this all makes sense to me

i use regane injector cleaner a few times a year and run 93 i know thats not the best idea. i also forgot to mention this started about a month ago and slowly got worse (feeling wise) and eventually turned code to cyl 2 misfire from random misfire. this is what makes me lean towards injector. read some other posts and seems on not the only one who has had an issue diagnosing it dam. well i could add it sure as hell still starts like a charm everytime with no issues. from what i read this could still be a million things

:drunk: :drunk: :drunk: :drunk: :drunk:

Get the compression checked out. Might be a headgasket leak. Since its on #2 just pull the plug and look at the top of the piston, if the top of the piston looks rusty brown its burning coolant. I wouldn't think it would be an injector because they usually don't go bad, clogged yes but not bad. You can take a 6" long 1/4" extension and tap on the injector to loosen the crud up inside the injector. Do that with the car running and you will know right away if thats the problem.

The only other thing I can think of is a cracked head. I had a cracked head about 3 or 4 weeks ago. I switched the plugs around and moved the wires around, switch the coil packs and ignition module, still had the misfire. Figured it was a headgasket so I pulled the heads, two cracks on cylinder #2. One crack between the valves and one from the exhaust valve to the spark plug hole. Hopefully it not that.

tried the tapping injector trick the ses went out for a few minutes and came back on but that was a couple hours after i tapped on it so ill take plug out put a led inside and see what i find

now its changed to cyl 6 misfire seems to be bouncing from cyl to cyl what is going on. autoparts store said try camshaft sensor.


what about a bad crank or camshaft sensor?

Its not gonna be the crank sensor. If you can get your hands on a scanner and look at the live data I would bet you still have a misfire on #2 still also. Your issue sounds just like my cracked head issue though. I started getting a mis on #6 after a while too. Did you get the compression checked?

Read through some of this http://easyautodiagnostics.com/index...articles_1.php. This will help you test everything yourself before you dropping money on a shop that may not know what they are doing. Say you test your coils and they are all good but the shop tells you that a coil is bad you will know for yourself before buying unneeded parts. I will search some at work tomorrow for ya though.

Didn't think about it before but it could be a vacuum leak too.

my buddy is on his way over to help with compression test. i just changed both 02 sensors didnt help. checked oil and coolant again both clean and proper level. i changed the coilpack for cyl2 im wondering if i should try changing all 3. but what is wierd is how it went from random misfire to cyl2 no its cyl6 i do appretiate ur input though it helps because im running out of ideas.

ok compression was 150psi on all 6 cyl the mystery continues.....

how are you going about getting your codes read? by the sounds of it the p0302 is cylinder two. a p0306 would be clinder 6 etc. IF you have tried plugs and wires... and swapping out coil packs. then maybe try getting a scanner that can get live misfire data. with that i want to ask... when the skip changed clyinders was your car parked at a differnet angle? dirt in the fuel rail could possibly cause this. recheck your connections. and if everythings good you try putting in a fuel injector. theres not much else it can be if you have verified your ignition is good, compression is good etc. if it was a vaccume leak or a sensor like cam sensor then it would effect ALL cylindrs. not just one or two. but this is where you need missfire data to get accurate results.

Did you check the factory service manual to see what the compression is supposed to be?

150 psi is more then enough for a stock engine. not only that but its equal on all cylinders. if you had 150/150/150/100/150/150 then there would be a problem.

edit:
so i went and looked for SAGs and found this. a little overkill but i figured id post for future reference. did highlight a few things.

Engine Compression Test A compression pressure test of the engine cylinders determines the condition of the rings, the valves, and the head gasket.

Important: Remove the Powertrain Control Module (PCM) and the ignition fuses from the I/P fuse block.

1. Disable the ignition.

2. Disable the fuel systems.

3. Remove the spark plugs from all the cylinders.

4. Remove the air duct from the throttle body.

5. Block the throttle plate in the open position.

6. Measure the engine compression, using the following procedure:

6.1 Firmly install the compression gauge to the spark plug hole.

6.2 Have an assistant crank the engine through at least 4 compression strokes in the testing cylinder.

6.3 Record the readings on the gauge at each stroke.

6.4 Disconnect the gauge.

6.5 Repeat the compression test for each cylinder.

7. Record the compression readings from all of the cylinders.

• The lowest reading should not be less than 70 percent of the highest reading.

• No cylinder reading should be less than 689 kPa (100 psi).
8. The following list contains examples of the possible measurements:

• When the compression measurement is normal, the compression builds up quickly and evenly to the specified compression on each cylinder.

• When the compression is low on the first stroke and tends to build up on the following strokes, but does not reach the normal compression, the piston rings may be the cause.

• If the compression improves considerably with the addition of three squirts of oil, the piston rings may be the cause.

• When the compression is low on the first stroke and does not build up in the following strokes, the valves may be the cause.

• The addition of oil does not affect the compression, the valves may be the cause.

• When the compression is low on two adjacent cylinders, or coolant is present in the crankcase, the head gasket may be the cause.

9. Remove the block from the throttle plate.

10. Install the air duct to the throttle body.

11. Install the spark plugs.

12. Install the Powertrain Control Module (PCM) fuse.

13. Install the ignition fuse to the I/P fuse block.

thats pretty much how he did it wow hes pretty good. i guess thats how he should be since he went to gm school. i also forgot to add the plugs were all clean and dry they looked alot better then i thought used plugs would look. hmmmmm so i wonder i could try a more intense fuel cleaner like a pressuized on at a shop. i never though to try seafoaming. yea i changed the coilpack for 2. i highly doubt i can have 3 bad coilpacks in a row especially considering i changed them 5 months ago but i could swap the other 2 out and hope it works. im just worried its something serious but my friend said with that compression test it ruled out alot of the seious stuff. and if it was limg or head gasket wouldnt the coolant be in oil and car running rough.?


also idk if this matter but i change my fuel filter every year and this year i went with a napa fuel filter idk if that matters its been in about 4 months now. and also idk if this matters but i never beat on my car

updates had it scanned at a shop they said they tested the car extensively and narrowed it down the either ign contrl mod fuel injectors or pcm. now i changed out my ign contrl module and it did nothing. heres is the wierd part though. when u take the car above 1800 rpm the misfire code goes from current to pending immature meaning the code is only showing up at idle or parked. so once the car gets moving or rpms are increased the misfire is going away. any ideas what that could mean or narrow down to?

Pull the upper intake and swap the injectors from the misfiring cylinders to known good non misfiring cylinders.

looks like its injectors did a pressure test on the rail so the psi drops to zero slowly takes about a minute. also when running the pressure is constanly jumping from 46-52 the neddle is very jumpy between those numbers so seems to me that must be injectors all along and my worst fear.

That might be the regulator then. Cheaper than an injector.