Recently I started to see P1145 codes (O2 sensor ahead of catalyst bank 1 - 3) and I see misfires on cylinder 1. The misfires only accumulate if I barely press the throttle; between 1000-2000RPM. At idle or higher RPMs the count stays at zero for the most part.
Last weekend I put in new plugs and swapped the #1 and #3 coilpacks and swapped the left and right O2 sensors and the misfires slowed down slightly but for the most part nothing has changed. I'm still getting P1145 every 3 days of driving and if I sit with the logger on and barely press the throttle I get a few misfires a second on cylinder 1 but no others.

On the bright side, the car is running great and it is just as powerful as ever. I am just concerned about the possiblity of an air leak or other issue that may cause cylinder 1 to have serious long term problems if I keep driving it like this. Any ideas what I should check next?

 

What are your afr's? You check fuel psi?

 

I have a durametric pro with unlimited vin's I'm on the SF Peninsula if you want to come and use it. Sounds like you are logging with some form of reader though. Could it be a faulty injector?

 

Next step I was going to log AFR's on both banks and compare. Can Durametric also diagnose fuel PSI? I wasn't leaning that way since there are no stumbles at all anywhere in the rev range and the only misfires are occuring on cyl.1 just off idle.
I thought maybe the boot between the intake manifold and the intake port for cyl.1 may have a small leak or maybe injector 1 is acting funny. They are 72lb injectors from EPL and I installed them 8 months ago.
One thing to note - the P1145 started a couple weeks before the misfire code but since they are on the same bank I thought they may be related.

Thank you to the other poster who offered to loan me your Durametric but you are correct in your assumption that I've got one

 

Michael, I had an elusive mis-fire problem many years ago that nobody could find - it only happened at very light, part throttle. We tried plugs, coils and more...turned out to be a bad tappet solenoid. The other side had a broken solenoid bracket, which I have heard can cause the same thing...

 

I've heard that the solenoid bracket is a common issue that is often overlooked. I am going to have the car apart next weekend and that is definitely on the list of things to check. The p1145 also points to valve train issues in its extended description oddly enough. Good tip John, thanks!

 

AFRs are looking good to me and each bank's AFRs are pretty close so...I'm going to have to dig deeper.

 

It's probably the solenoid bracket, as John says...sometimes hard to see it cracked on the engine, but as soon as you unbolt it, it comes off in 2 pieces...good luck with the hunt...

 

I bought an extra bracket to keep around I bet thats it as well. cheap easy fix

 

Thanks to everyone who has replied so far. Regarding the solenoid bracket, is it simply removed and replaced with two bolts or are there any special instructions I should be aware of to make the job easier?

 

That's it, however, if they are not broken I would switch solenoids to other sides and see if the mis-fire moves to bank 2. I had a bad solenoid on one side causing the problem and a broken bracket on the other side that did not cause any issues. I replaced the solenoid with the good bracket, as that was my problem bank, on a $120 gamble and it worked....so the units themselves can go bad.

 

Here’s the deal…I changed my plugs again with FR6-LDCs and also my coils this time. The cam solenoid brackets were in good shape so I swapped the cam actuator solenoids betweek banks also…just took it for a drive and STILL getting these damn misfires only on cyl1. The accumulate quickly at low throttle and not really in the higher rev ranges when watching with Durametric. Strangely, every couple minutes they remain at zero, and then bam, they start accumulating again for 10 minutes or so…then back to behaving good. I'm not talking about when Durametric resets to zero when counting misfires every minute or so...I mean that the misfires just stop for a minute, start for a minute, stop...it is so frustrating! I am running out of ideas here. My next step is to swap the injector on cyl1 with cyl3 and see if the symptoms move. Before going through that horrible process, does anyone know definitively if misfires can be caused by a faulty injector, or are they only caused by ignition problems. I definitely do not want to mess around with the injectors if they can't be the cause.

 

Any metal shavings in the oil filter? Checked that lately? If there's slivers in there those end up blocking/clogging up the solenoid... Hope it's not a lifter coming apart.

 

The solenoids looked clean when I swapped them and the small amount of oil that poured from the heads when I did so was clean, but I'll inspect the filter tomorrow. If it were a solenoid problem wouldn't more than one cylinder in the bank have misfires?
Also, if anyone would know if an errant injector could cause a misfire you would Sharkster...is this a possibility or should I leave my injectors alone?

edit - there is zero tapping sound from the engine that would lead me to think it was a lifter either.

 

Well it's an easy thing to do just look at the filters and make sure there's no metal shavings in there just to be sure. You won't really see the slivers in oil you drain....

Good sign that they were clean tho. Reason I bring this up is a car came in with similar codes and sure enough... Those lifters do fail sadly. Wasn't driven enough to trigger more misfires in other cylinders.

We've certainly seen leaky injectors over the years (seimens ones that folks use for 700hp kits). Rare but happens. A 997tt also had one bad injector which caused a nasty issue too but factory ones seem immune. That can lead to misfires too yes.

On the sound if you have a loud enough exhaust it's pretty quiet as far as the sound. But hopefully that isn't an issue anyway.