Slight miss at idle and low RPM acceleration

[soundquest]

I have the 3.4L version Pontiact Torrent (base) with 195,000 miles on the ODO and have a slight miss at low idle (slight enough that it only trips a CEL P0301 under just the right conditions). At idle, the RPM's bounce anywhere from about 712 to 770 (and the needle dances around quite a bit). Acceleration is pretty good from a dead stop (I can chirp the tires). We just aquired the vehicle recently and I performed an extensive tune up on it (plugs, wires, throttle body removal and cleaning, PCV hoses cleaned, new water pump, new tensioner, belt, oil, filter, valve cover gaskets, etc). This is my daughter's car now (new driver) and am wanting to make it as safe and reliable as possible. I have a new ignition coil on order, and new evap purge vent solenoid (considering installing a new EGR valve since I know they can be problematic on these). Am half way through a tank of Regane All-in-one FI and combustion cleaner. I know the intake manifolds on these like to leak, as do the head gaskets (but these were both serviced under warranty early on in the life of the vehicle). I have no oil in coolant or viceversa. Will be running an intake decarbonization procedure on this soon. Looking for any insights into this low idle miss. Thanks in advance.

 

[92 Sunbird LE]

Bad or clogged injector is my guess, run some fuel injector cleaner in the tank a couple of fillups to see if it helps, seafoam works wonders too. Last resort, take it out, blow in some carb spray to clean it out, and check the screen inside it to see if no dirt or rubber bits from hoses are clogging it or just take it to have it flow tested.


Doug in P.R.

 

[soundquest]

Thanks. I am about halfway through a tank of gas with good FI cleaner running through it. Hopefully I will see tomorrow after installing a new ignition coil if that is/was the cause. Vehicle also lurches from a dead stop if you take your foot of the brake pedal and let it pull forward under idle power.

 

[MarkEggert]

Thanks. I am about halfway through a tank of gas with good FI cleaner running through it. Hopefully I will see tomorrow after installing a new ignition coil if that is/was the cause. Vehicle also lurches from a dead stop if you take your foot of the brake pedal and let it pull forward under idle power.

Just as an FYI, my base 2008 Torrent with the 3.4 does not lurch forward when releasing the brake. It barely moves when releasing the brake. I also notice the tach bouncing around a bit at idle although the engine sounds smooth with no misfire on mine. I just turned over 153,000.