Oil light, backpressure, knocking, rough idle and start...pleas help
Hi. My 2006 g6 3.5 gt cope has been a huge nightmare for months now. I have had to replace injectors 2 times, icm, plug wires, spark plugs, upper/lower intake manifold gaskets, valve cover gaskets, air filter, map, maf, battery, pre cat or sensors, purge valve solenoid, starter, oil filter adapter gasket and just finished redoing the entire engine harness and grounds because of numerous weird issues that continued happening after everything was replaced. Then had the throttle body not working because of pins internally broke. Which took about 4days on non stop research to get any info at all on it because every diagram/scechmatic/forum/mechanic all showed and said the same thing, that it is a 6 pin harness connector...mine is a 20 pin with 17 male pins on the throttle body/iac/tps (all in one) and the connector harness from the ecm had 13 female. Figure just some aren't ised by the g6, idk because I've still not found but 1 mentio of this mysterious 20pin harness and no replies were given.
So after a lot of testing and process of elimination I finally narrowed it to the internal breaks so new tb fixed that.
Well now to throw some backstory for reference...
I had rough idle always, sounds louder than it should with a slight/faint knock I'm assuming it's lifters or such as it increases with rpms. 130k on the car, run penzoil ultra platinum synthetic 5/30 oil with the Fram synthetic filter, cai (not oiled), ngk iridium plugs, flushed coolant to remove traces of dexcool 2 times this month.
So the starting issue seems to be happening with everyone but can't seem to find a solution.
I assumed I had a leaky injector because it would only start if I floored it allowing it to drain the gas and after starting it smelled of gas strong for about 10 seconds. Pressure would drop at the rail within about 30min to about 10psi. And scan tool showed misfires on 2 cylinders but 6 was the most and would be completely random, 1 drive cycle it'd get 2 and then the exact same drive, same speeds, Temps, etc and it would show 30. So I had already replace all electrical so narrowed it down.
I pulled the plugs to check for signs first aand was confused because the 1 and 6 cylinder were ok, dry, but all had signs of burning lean.
Cyl 5432 had black gunk on them but 4 and 3 were dry and 5 and 2 were moist.
Did not look like oil at all really, so idk.
So long story short, I went ahead and tore it down to the head again and replaced everything.
Starting was perfect, almost too quick, like hardly had time to get my hand off the key and it was fire up.
Test drove and it and for the ffirst time since I've owned it I actually felt it drive like it should...way more power than it used to have!
I noticed that the oil light was on before I left, I checked level and it was full, gaskets were new, brand new oil and filter. So I assumed it was an issue with the sensor since this cars electrical is a joke.
So I decided that I'd drive about 12 miles or so and check out the scene...well the whole trip was fine up until I pulled in the drive and then heard an odd ping sound and a bit of rattle.
Killed it, popped the hood and the hot air about took my skin off!
I had been watch all gauges and monitoring live data on torque and temp never reach over 205, not even high enough to kick on the fans.
It was obvious without a temp gun that there was at least a 50 degree difference between the reading and actuaactual temp under the hood.
The engine was making loud ping/knock/clunk sounds randomly anywhere between 3 and 40 seconds apart and all came from what sounds like the upper intake manifold by the firwall, cylinder 1.
This noise is simular to the normal expansion contraction sounds made when an engine cools except WAY WAY louder and confined to one area (not heat shield) and longer spans of time between pings.
So I checked everything I can think of, no vac leak, temp sensor ohmed out, coolant was flowing, no leaks of any kind, coolant holds pressure, no cel, map and maf seemed to be reading as well as evap and o2s all read fine on torque.
I originally thought that this oil light was just a fluke or bad sensor but I ran to warm 2 more times in park while watching live data and listening and both times I had to kill it at about 180 degrees due to a weird rattling ticking sound coming from somewhere between the center area of the upper intake to the lower.
I don't have a way to check oil pressure but I figured an easy way to test if it is not getting oil circulated (which is the only logical answer) would be to pull the dipstick after its running because there would be nothing on its really.
So I did and as I figured the level was the same meaning my oil is not get pumped up.
So that explains the knocking and some of the heat but the start issue had also Come back as bad as ever. The temp gauge not once got near the hot mark. I got zero fault codes. Live data showed what was actually the best readings I had seen on this car by far
Intake pressure held steady showing no leaks really. Maf would jump and drop as expected dependent on tp, tps went up normally and steady, stft on both banks was at 0 and never were more than 3 off each other, left was at 0 and would go to 6 to -6 depending on load (best left I've seen was -26 and -28 on both previous) evap shows its working, load was fine, timing between 15 to 35ish dependent on tp, o2 sensors were looking perfect.
Well after the new rattle sound began the left dropped to -6 both banks and bounce between -22 and -6 And after cat o2s didn't change voltage at all when throttle so they are now not working.
Then I noticed that the intake manifold pressure was 5 psi steady at idle, but when reved to 2500 and held it dropped down to 2 to 3psi and stayed there.
Normally it would go drop as the tb is opening and pressure is released but then as the engine sucks it in the pressure builds back up and then some.
Out of 8 different times I reved it, once it went up like I expected and went to 14 psi I believe.
The only thing I can think of that makes sense would be excessive back pressure which isn't allowing the air to escape therefor keeping the pressure from building up...so I'm assuming my cats are bad!
Also would explain the temp issue cuz the heat couldnt escape and built up but I would think the sensor would have shown the temp was higher but it didnt.
So..that's the jist of it..there's tons more to the story but this is already insanely long so just ask if u need any other info.
My situation is this. I am currently out of town with this unrivaled car 3hrs from home and have til Tuesday to fix it or pay to have it towed that far.
I have replaced just about everything on it and I'm tired of dumping money into it. Spent 2000 in last 2 months already and it still needs new tires, exhaust (oh yeah, forgot to mention it has several leaks, all after cats, big leak at the 1st flex and 2nd and several smaller ones all the way through), shocks and struts are completely shot, needs another steering shaft (last one lasted a whole 2 weeks/403 miles) and several other things...so it sucks I'm gonna have 4 grand on top of what I paid for it in a car I'd be lucky to get 2500 for!
so I just need advice on what you guys think...my brain is overloaded, I've literally developed arthritis in my fingers from spending 6 to 10 hrs a day researching. I have done all I know how to do and think I have it figured out but I don't want too moss something and cost me more money, time, and being away fromy family.
so any thoughts on what would continue causing the starting issues
...what would cause the engine to be significantly hotter than the coolant when the sensor is good. (possibly the pressure tank cap?)
....what would cause my oil light to come on when my engine was spotless inside and out, always geta high quality oil and filter, never an issue before)
....what about the intake pressure dropping and staying there and the fuel adjusting for a rich condition after the drive I took where it ran amazing.
...why did my back o2s stop reading after I drove it?
...what could the rattling/tapping noise that appeared around cyl1 after driving it be?
...what about the loud ping clunk sounds that come from between the upper and lower manifold centered and btw its a metallic sound and loud....almost what it would sound like if you hit a hammer inside the lower manifold...also it occurs during warm up, driving, idle, ign off which means it must be a non mech issue but what and why now?
...would the radiate exp tank cap cause any of this?
basically any info or ideas would be great.
I'm assuming this may be more than 1 issue, like clogged cats, exhaust least, and somehow I have a clogged oil pump..but I really wanna make sure I don't replace something that isn't needed right now...and I don't have access to any pressure testers or specialty tools now so I have to go by what I already learned and scanner data.
And lastly I'd like to know how it's possible for the ecu to not throw a code or even have a potential fault pending when so many things are horribly off!?