Rough idle at a stop

[Guest]

Hey guys, new here to G6 performance, I have an 07 G6 base 2.4 auto with 170K on the odometer. Timing shattered at 168K and have since replaced the camshaft and counterbalance shaft timing sets entirely, checked 4x that all timing marks were aligned, have replaced the entire cylinder head, new timing cover, oil pump and water pump, new spark plugs, replaced exhaust cam sensor pigtail, and new camshafts.

Cold start rattles for a few seconds then fades away. Acceleration under load (such as going up hill) engine rattles badly, and then when I pull up to a light or a stop sign the engine misses, stutters, pulls and shakes, causing the whole car to pulse about 3 jerks every second.

OCCASIONALLY we get a check engine light which we can't read because the computer doesn't link to a reader. (Have spent hundreds of hours searching the internet and have seen absolutely ZERO related postings that had been solved, only answer being "dealership could get a code but wouldn't say what it is unless I paid for diagnostics")

Paid 2500 for the car and so far am in 2000 just in parts. Anything helps at this point.

[Guest]

Re: Rough idle at a stop

Have double checked compression, before cylinder head replacement cylinder one was 145 cylinder 2 was 155 cylinder 3 was 165 and cylinder 4 was 135. After head replacement compressions are 150, 155, 157 and 145.

Have checked all 4 coils for spark, first with spark tester and second by removing coil connectors one by one to see how idle is effected, with absolutely ZERO change. Idle remained exactly the same regardless of if and which coil was unplugged.

Car still runs perfect while cold, while ticking obnoxiously for the first 3 seconds after start up, then runs smooth until it has been at operating temp for 25+ minutes at which point it begins tocking again like a diesel Jetta and knocking hard at idle.

Oil level is where it should be, as is coolant. There is fuel in all 4 cylinders, no vacuum leaks,

This engine is testing my patience, which is usually quite abundant....

[Guest]

Re: Rough idle at a stop

Update: had the local GM dealer look into it, miraculously their code reader got 4 codes all related to timing and timing hydraulics. Mainly exhaust not functioning hydraulically. Couldn't replicate the infamous communication link issue.

So replaced both phaser gears, both cam sensors, both solenoids, as well as the spring loaded timing tensioner after finding a bit of slop in the top of the chain. Entire timing and counterbalance system is still brand new, less than 500 miles on them in 6 months now.

Still misses at idle, still chatters and rattles under load between 1000 and 1800 RPM's. Still has a CEL that I CANNOT READ.


Literally the ONLY parts I have left in the block to replace are pistons, rings, wrist pins, connecting rods, rod bearings. And main bearings.


Bout ready to say F#%& pontiac and sell it.

Would be nice if I could get some damn feedback on here..... thanks.