1999 Chevy Monte carlo  3400 V6 SES light problem.
Finally got a OBD 11 tester and i have a P0300 and P0302, or a misfire in #2 cylinder. Rechecked
plug and wire, replaced wire, replaced coil for that cylinder. Sounds a bit better but still idles like a
misfire, tester shows a misfire that is the only bad cylinder whats next, resistance on the injector, or
would that have shown up on the tester?

Answer:
Thank you for the tip / donation.
Assuming there is no engine mechanical problem with that cylinder- like a rocker arm stud has pulled
out of the cylinder head, most probable cause is the injector. Scanners dont detect specific problem
(injector bad) just the type of fault. Our injectors today dont usually fail because of low resistance
anymore. They almost always fail because they are plugged.

Here is a little trick, with the engine at idle, and missing, take a socket extension and tap the injector.
Very lightly at first a few times, then a LITTLE harder if it has not cleared up. Be careful not to tap too
hard and crack / punch hole in the injector. This procedure will almost always free-up a stuck injector.
If it does, it may quit again in a day or two, or may last a month- hard to say.
If the injector does free-up, would suggest an injector cleaning service and fuel filter after replacing
the bad injector.
Fuel injector problem causing misfire code P0300, P0301, P0302, P0303, P0304, P0305, P0306 on GM 3.1L and 3.4L V6 Engine. Also know as 3100 and 3400.
Comments
4-5-11
I recently purchased a 2005 Chevy Impala here it is only 10 days later and it's idling so high that I
don't even have to put my foot on the gas it just takes off all by itself but you have to keep your foot
only on the brake at all times. Please help?!
If the check engine light is on, you need to have the
codes scanned. You may have a problem in the
Electronic Throttle Control (TAC). Or maybe it just needs
a
cleaning of carbon from the throttle.
8-9-11
my 2007
Chevy Impala doesn't want to take off fast it takes time an then it shakes an the rpm
moves it self
Could be a lot of things. Engine misfire, low fuel
pressure, MAF sensor, ECT. Get a scan of the computer
codes even if the check
engine light is not on.
1-20-12
I just replaced my spark plugs in my 2009 Chevy Impala with the 3.5 l engine. My service traction
control light came and its running very rough. Could this be a faulty plug or incorrect gapping? I
installed the Pulstar pulse plugs.
2-2-12
i had a random multiple misfire on a Chevy Tahoe i changed the spark plugs,wires,dis cap rotor
button,and 6 of 8 injectors the car ran fine after the work but the next day it started right back with
the same thing.
If after changing all that, and basically guessing, the
truck is not fixed. That is why we always stress doing
proper diagnosis. If that were done, you would have
saved a lot of time and money. The problem depends on
what cylinders were misfiring. If they were all the Odd
numbers, then this may be a common problem of the left
catalytic converter being plugged. If it only happens
when cold, that could be an intake manifold gasket
leaking vacuum. You could also have a contaminated
gas. A sample would need to be taken.
Problem with my 1997 Chevy Monte Carlo LS.
3.1L V6 engine
Check engine lights flashing and
OBDII codes p0300. Change all  sparks plugs and wires. Why does my
check engine light have this code p0300. We   replaced coils and spark plug wire.

Answer:
First you need to find out which cylinder(s) is misfiring.
If plugs and wires were replaced, another common cause for misfiring is a   burned /
corroded ignition coil.
That should have been obvious while  replacing the plug wires.


Problem with my 1995 Monte Carlo Z34.
3.4 DOHC.
Work done to repair this problem = Replaced
Idle Air Control Valve.
My 3.4 idles VERY rough and dies cold. When warm the idle is somewhat erratic
and although a little high it is tolerable. I cannot find any vacuum leak which is what
I suspect. I replaced the idle air control valve and am now suspecting the EGR (it is
digital). I'm not sure if it can be cleaned or not...... Any suggestions?
Answer:
This IS a classic sign of a vacuum leak on the Dual Overhead Cam Motor (DOHC).
Especially the lower intake manifold gaskets as they meet the head, the PCV valve
pipe on the drivers side rear of the rear cylinder head, or the brake booster
vacuum hose.
Concentrate spraying carb cleaner on these areas when warmed up to see if the
idle will change. Be sure to stay away from any ignition source, as the spray is
VERY flammable.
Try tightening down the upper intake a little more and see if that helps. I had that same code come
up on a 3400 and it was the upper intake.

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3400 V6 Engine Misfire Repair Trick