On the first start of the morning, I have a rough idle . It persists for 20-30 seconds until the car steadies out at around 600 rpm, at which point the car is smooth as butter.

During this rough idle phase, I will occasionally get a CEL with misfire codes. I started a thread on this earlier when I was only having a misfire on one cylinder. Now, I regularly get them on all cylinders on bank 1 (1, 3, 5, 7).

The most recent code read was this:
P0301 (Cylinder 1 Misfire Detected)
P0303 (Cylinder 3 Misfire Detected)
P0305 (Cylinder 5 Misfire Detected)
P0307 (Cylinder 7 Misfire Detected)
P1316

When I only had one misfiring cylinder, I suspected a bad coil/plug or even a weak battery, but seeing all on a bank leads me to believe it is something else.

I am new to Jags, but read on here about the importance of monitoring short term and long term fuel trims. Using an ELM and Dash Command, I observed the short term fuel trim ranging from -10% to -20% during this time, even though my long term trims are around +3%. I cannot see a way on Dash Command to get fuel trims per bank. Doesn't this suggest very rich running during start up?

I can turn a wrench, follow instructions, have rebuilt engines in the past, and have all the documentation available here. What I'm looking for is some guidance as to where to start trying to track this down. I took it to the shop last week and they were unhelpful (cleaned throttle body, cleaned injectors, and reflashed ECU) and the problem remains. What could effect all the cylinders in a bank this way?

My car has around 46k miles on the odometer.

 

Not likely that you'd lose all the coils on one side and an air leak doesn't seal itself in 20-30 seconds. I'd be looking at what controls power to the coils and their firing sequence.


This is first on the list of potential reasons for a P300 series code ......... ECM to ignition coil primary circuit fault (cylinder misfire detected DTC also flagged)

 

Thanks for the suggestion, I started there and have a bit more to report.

Battery voltage this morning: 12.14 volts
I checked the ignition coil supply voltage on bank 1. Each cylinder read at 11.57 volts. This seems OK.

I then checked the ignition coil supply ground on bank 1, measuring ohms between pin 3 (the black wire) to ground for each of cylinders 1, 3, and 5. I did not remove the coil wire for cyl 7 for this test, and I did not pull any from bank 2 (2, 4, 6, or 8). This is where I got what seemed to be a strange reading: ~200 ohms for each for 1, 3, and 5. This number declined over time until about 30 minutes later I was able to measure 0 ohms.

What would cause these pins to carry resistance that trends towards zero over time? If these are connected to ground, shouldn't that be 0 ohms all the time?

Looking at the wiring diagram, it looks like bank 1 grounds join together at PIS43. Where is this located? Is it at or near the ground point G26? Where is G26?

The car now starts terribly (after hooking up the coils again). During startup, I am getting short term fuel trims of around -25%. Could a bad ground on the coils cause the car to run rich?

 

Reran the tests this past weekend and believe my faulty measurements were due to a weak battery in my DMM. When I ran the tests again (with a fresh battery in the DMM), I confirmed a solid ground at each coil. On to the next test.

 

So I have a potentially bad development. The misfiring upon startup is happening with greater frequency (nearly every day). The misfires are all on Bank 1 (usually 5 and 7, sometimes 3 and/or 1). The last few times this has been happening, I have noticed white smoke from the tail pipe and very sweet smelling exhaust until the engine is warm. I suspect a bad head gasket, one that starts out leaking until the engine is warmed up. Ugh.

A few questions:
(1) Are there any other explanations for coolant passing through the exhaust?

(2) If yes, how can I confirm/rule out those other alternatives?

I am a bit frustrated because it is a low mileage car (~44k miles), I bought it six months ago, and I have never overheated it.

 

One other thing, in case it is related. Earlier this year, I paid my mechanic to replace the valley hose (and all other coolant hoses). I did not have this current misfiring / smokey exhaust problem until after that. Could he have disturbed something during that procedure?

 

I had similar symptoms plus other weird things going on and sometimes the misfire codes were all one bank and sometimes random. It all went away when I bought a new battery. It cranked fine on the old battery but the voltage dropped to 11 volts when cranking and the computers didn't like it.

 

The ground may be a non-issue as I think you'll find from the workshop manual that the coils are fed with +12V and the PCM makes a ground to trigger them. So checking the +12 is more useful

 

Thanks for the replies. I am going to run a coolant block test to see if there are any exhaust fumes in the coolant. My hope is to confirm whether the smoke/smell from the exhaust is burned coolant or (hopefully) just the smell from excess fuel going through the. I'll report back.