Your cam maybe is wearing out.

 

If you got a random missfire. It can be just about anything. Spark, Compression or Fuel.

You can not tell how good a spark plug wire is by looks. They build resistance over time. They can look great and be killing you ignition system by forcing real hot spark. Your coils are capible of firing 80,000 volts.

Maybe you should think about taking the car to a mechainc who works on driveability all the time. By all mean do the routine mantenence first and replace the wired if they are older then 6 years. I can think of about 15 things that can set a random misfire you could go broke throwing parts at your car but you might get lucky. (throwing parts at a car is a term we use when someone has no idea what is wrong with their car but they keep replacing part with the hope it will fix it)

 

Well I will test the resistance in the wires, but even a hairline crack in the wires could be the cause so maybe ill check for spark with a spark plug tester.

I will have to start from square one and go over the entire ignition system, than checking the compression and so fourth.

Thanks for the comments

 

can driving with a miss damage the engine over time?

 

If you are testing the resistance with an ohms meter your wasting your time. The way the wire reacts to the 9v the ohms meter will put thru it has nothing to do with the way 30,000-80,000 volts goes thru it under load. The only way I know to check plug wires is a automotive oscilloscope. Of couse the price of the test will be higher then the price of the wires.

I have seen people go crazy tracking down a miss. I had one customer that installed an entire ignition system and a new fuel injector before he brought the car in. 15 minutes on the engine analyzer I put a new plug in cylinder 4 and it was fixed. He was pissed he said no way that fixed it! He already replaced the plugs. My guess is he had a bad plug and in installed a defective plug or cracked it during installation (very common).

I am not saying your car can be fixed in 15 minutes but without a scope how do you know it is not a cracked plug?

 

This depends on what is causing the miss. If a cylinder is not firing then you are dumping raw gas and O2 into your exhaust. This is very hard on the Cat but will not damage your motor. It could cause carbon built up on your valves but most of the time that just blows out once you make the repair. Same thing if the cylinder is running to rich.

If a miss is because of not enough fuel AKA lean it is VERY hard on the motor. Lean causes massive heat spikes. The cylinder and piston will get so hot they will ignite the fuel before the spark fires. This is called pre ignition. Luckly our cars have knock sensors that can "hear" pre ignition and with retard the timing to reduce cylinder pressure and temp. The higher temps can still hurt the motor even before the pre ignition happens. It will cause pitting on the piston top and the rings.

The worst case for damaging a motor would be crossed to shorted pug wires. Igniting fuel when it just starting to compress can cause a major failure. If you cross a wire during a tune up it not to bad because most people would never try to drive the car and there is not a lot of fuel involved at idle. But if you have one spark plug wire with that building up a bunch of resistance and it has been rubbing agains another wire for year then at some point while you are running the crap out of the car the spark decides its easier to shoot through this other wire then to go thru the one I am suppost to,,, boom.

 

It could very well be a cracked plug, but considering I just upgraded to NGK platinum plugs and it making no difference I just thought I'd rule them out. It's a random misfire, so all cylinders are firing but not correctly. I had this problem with my Neon and it turned out to be an arching spark plug wire.
The spark plug wires are NGK and look fairly mint, but considering my luck I will replace the wires and hope it fixes everything! lol

 

At this point its best to just take it to a shop. It sounds like guessing to me. A shop will usually only charge one hour labor for a diagnosis. That's about $80 in my area.

 

Taking it to another mechanic takes the fun out of finding the problem and fixing it though. That might be my last resort as I don't mind throwing some new parts on to find the issue.

I have a feeling it could be a arching plug wire, but it's a random/multiple misfire so I don't see how it could just be 1 plug wire.

My OBD2 test (not throwing CEL codes, this is a seperate sensor scan test) showed this (below). Could an 02 sensor cause the issue? I checked the 02 sensors and they are fluctuating the voltage fine, so I don't know why this test is showing that it's a critical failure. (The X infront means critical failure)

$O2 $O4 EVAP canister loading test
$O2 $10 EVAP weak vaccuum test pass 1
$O2 $11 EVAP purge leak pass test
$O2 $12 EVAP small leak vaccuum decay rate test
$O2 $16
$O2 $20 B1S2 rich-lean switch time in fuel cut-off
$O2 $21 EVAP purge leak vapor fail test
$O2 $26 EVAP excess vacuum test 1
$O2 $30 EVAP weak vacuum test 2 vacuum
$O2 $31 EVAP purge leak vacuum fail test
$O2 $36 EVAP excess vacuum fail test 2
$O2 $40 EVAP weak vacuum test 2 vapor
$O2 $46 EVAP excess vacuum pass test 2
$O3 $O1 AIR bank 1 test
$O3 $O2 AIR bank 2 test
$O4 $20 X Bank 1 O2 sensor
$O4 $30 Steady state catalyst test bank 2
$O6 35 Oxygen sensor heater time to activity - B1S1
$O6 41 Oxygen sensor heater time to activity - B1S2
$O6 55 Oxygen sensor heater time to activity - B2S1
$O6 61 Oxygen sensor heater time to activity - B2S2
$O6 $OC X Misfire counts for the last / current driving cycles (double check)
$O6 OD X (May not be $06, $07 0D is EGR decel test)

 

Hell yea dj