Why is cylinder 2 misfiring?? even stumped a mechanic
Day 1: Knock sensor 2 code was active (but the car has a light knock when
over-revving). Noticed the car was running pretty rough, with a lower than
normal idle RPM. Also notice it got rougher once I reached 40mph on
fourth gear. Then noticed oil pressure light was flickering occasionally
(went to a forum where everyone said the oil pressure light was likely
sludge or particulates clogging the oil intake screen). So I used the ZMAX
fuel system cleaning kit, which came with an engine oil treatment, fuel
system cleaner that was sprayed into the intake and fuel additive. I drove
for about 100 miles, during which the oil pressure light turned off. Then
after driving, I removed the oil pan, cleaned it, scrapped off all visible
sludge from bottom of engine in the oil pan area, then scraped all sludge
and deposits off the oil intake screen (which was very thick). Also did a full
oil change with full synthetic oil and new filter.
Day 2: car has been running much smoother for about 2 days. then check
engine light begins to flash at me along with the oil pressure light
intermittently, as well as rough idle and high speeds began again. So just
in case i performed another oil change using a detergent, as well as
flushed clean oil through the system to make sure all detergents are rinsed
out and replaced filter again. This took care of the oil pressure light again
(think i got it all this time lol). As for the check engine light, I had the codes
checked which showed an evap system leak, knock sensor 2 and cylinder
2 misfire. by an amateur mechanic friend, I was told that the evap system
leak could be the cause of misfire. So I searched the evap system and
found a vacuum hose that was disconnected from the air filter housing. I
reconnected it and waited till morning to check if the codes had been
day 3: took car to autozone to have codes pulled. This time the evap leak
code is gone, however cylinder 2 is still misfiring and now cylinder 6 is
misfiring. got new plugs and replaced cylinder 2 and 6 plugs. cylinder 2 old
plug was caked in black carbon deposits and even appeared as though
the arching metal on engine side of plug had been slightly warped.
Cylinder 6 plug was immaculate aside from a light layer of white ashy stuff.
Then checked codes again. Now only knock sensor 2 and cylinder 2
day 4: troubleshooting the misfire, I know the spark plug is good. I also
switched up coil 2 (on misfiring cylinder) with coil 4 (a known good
cylinder/coil/plug/wire/injector). The misfire did not follow the coil, so I know
the coil is not the issue. Then pulled cylinder 2 plug out, connected it to
boot and tested to see if spark will arc from the plug (effectively testing the
plug, the wire and the coil) it sparked very strongly. So now I'm down to
injectors. I did the same process of switching the "questionable" injector
with a known "good" injector. The misfire did not follow the injector.
conclusion thus far, I have a knock in the engine, so ofcourse the knock
sensor is throwing a code. Cylinder 2 is misfiring. Cylinder 2 ignition coil,
wire, plug and injector is working properly.
Question: Why is cylinder 2 still misfiring, despite tests indicating the coil,
plug, compression, wire and injector are good?
Run a compression test to determine if the engine is healthy.
I'd do a blow down test on #2 cylinder. The heavy deposits are telling me that this is the big monkey in the room here. The ESC setting the timing back in trying to quiet for severe knocking also say that something mechanical is gone bad herE too. BTW: the flashing CEL should also have a hammer in the headrest to whack the driver in the head at the same time to make them know that the silly light that's flashing indicates the catalytic converter damage IS HAPPENING AS YOU DRIVE THE VEHICLE.
Okay so i ran the comoression test and all cylinders have over 180, except cylinder 2. Cylinder 2 has a 0 compression reading. What does this mean? I know this is quite possibly the worst result and most expensive to fix. But i wouldnt even know where to start.
At this point, pull the head and you'll get a better idea. This sounds like collapsed ring (s) that might have allowed the piston to melt along the side...... or a holed piston. Zero compression is never a good sign. If a valve were burnt, there might be SOME residual compression, but ZERO is pretty indicative of serious damage. Further testing is counterintuitive at this point since all repairs start with "Remove cylinder head......" You might have dropped a valve through the top of a piston too. Anyway .... like I said ..... pull the head or get a shop to perform a tear-down estimate and prepare for some negative cash flow. I never suggest buying a used engine, after all .... you've allready GOT a used engine.
BTW: I apologize for your original "mechanic" who was "stumped" for something so obvious.
With zero compression you could have a blown head gasket, bent or stuck valve, broken connecting rod, piston damage or a hole in the engine block (least likely). With zero compression no further diagnosis is necessary as engine dis-assembly is necessary. A tear-down will determine what the exact cause is. Glad you are making progress, but wish the news was better..
Forgive me I have a question the spark plug cover and wires on the left blew off I had to replace with new cap to cover for the plug it is still running ruff and dies often when I try to turn a/c on the car dies 2000 salary 6 cy almost 300 thousand miles please help I have a engine light on as well thank you glenda
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