"... evidenced..." *NM*

Maybe it's like a waxed car car goes faster, but I swear the mpg has gone up by a few.
For as much as a couple years, the car has had a slight miss at idle as evidenced by the exhaust having "bup" evey few seconds.
That's gone for at least now, and the rpm range has a more turbine-like smoothness. Also, it maybe just the contrast to my trusty old CRX Si I was driving all week, but the car pulls like a freight train.

I suppose the "bup" can indicate the eventual failure of a coil, and wonder if an analyzer can narrow it down to the cylinder. That'd be neat, as a preemptive changeout could be done way before failure.
But not like this:

"Ive just picked up a fault in the AE35 unit"



Edited 2 time(s). Last edit at 04/28/2024 05:15PM by Laz. (view changes)

The #5 coil might've gone because of heat stress from the loose pre-cat below it, but...
(and not definitively knowing what path exhaust gases take) there was no soot on the coil, nor any adjacent surface. With direct injection, quite a lot is produced, as evidences by the tail pipes. Perhaps air was being pulled in, causing the O2 sensor to "see" a lean condition, and enriching the fuel-air mixture, the result being a relatively high fuel consumption. With the tightened sensor, the system is taking proper readings, leading to the better mpg.

Coils 1 and 3 (passenger side) are now changed out, and only coil 4 on the driver's side "needs" to be pre-emptively done, but the very-difficult-to-reach location makes it a dealer job.
Thoughts on the previously mentioned loose O2 sensor:
The passenger forward sensor was even looser than the other bank's. I gave the lead a bit of a ccw twist before screwing the sensor in, with the hope of counteracting some of the ccw tension, but I don't think it helped much. I didn't force it further so as to avoid possibly damaging the lead's connection to the chassis wiring. Being the coils are not the easiest things to get to, I sure didn't want to deal with a busted connection somewhere in the dark recesses of the car.
I currently entertain the hypothesis that the factory can install the sensors while the engine is still out, and the leads are free to turn. It's afterward, when spark plug or coil replacement comes up, the job in doing each forward piece is a lot easier with the sensor out of the way. Then, when being reinstalled, the issue of ccw torque comes up.
One other thing: the nature of the sensor threads is such that when tightening, the piece is loose... it's loose... it's loose... then it's tight. I found once it's home there's very little turning, if at all, that can be done, even yanking on the O2 wrench with about 80% of what I could do. I'll check on them at least with each summer/winter tire change.



Edited 1 time(s). Last edit at 05/20/2024 09:11AM by Laz. (view changes)

I have removed the coils on my 981 to change spark plugs twice over the years - I was able to remove all the coils without difficulty. I'm surprised to read that #4 requires a dealer visit. I am well equipped with various tools - maybe that explains why.

It seemed out of reach even visualizing from underneath, let alone just taking the wheel off.

Mine is a 2014 Boxster S. I do it through the wheel well. I don't know what to say except I am used to working in tight spots and I have a ton of tools.

Laz--You need to get a lift before you hurt yourself if you are going to maintain your 981.

Are you changing all coils because of the #5 problem?
Is the #4 coil the only one that requires a dealer service?

In the past couple years, because of code warnings coming up,* but no actual performance issues, and not wanting to get into the job myself, coils 2 and 6 were changed by the dealer. A few weeks ago, when #5 went, it was sudden and catastrophic, with the engine bogging and the car barely able to move. As you know, I changed it myself. This event prompted me to change out the remaining original coils, of which 1 and 3 I was able to do with my limited facilities. The remaining one, #4 is the most sequestered, and therefore a "dealer job," as they are familiar with the procedure, and I have a nice relationship with the service department.

* Aside from the pertinent coil codes, the initial warnings each time have been, if I recall correctly, lost of PSM and Auto Stop/Start. (A bum coil will affect engine control, and those features, especially PSM, depend on it.)

Using a cylinder-specific analyzer can help pinpoint which cylinder may be at fault, allowing for a preemptive coil replacement before a full failure occurs, and this targeted approach avoids the frustration of vague fault codes like “AE35 unit.” While ignition components are the usual suspects, it’s also worth remembering that worn bearings in engine accessories or the drivetrain can subtly affect smoothness and responsiveness, so keeping an eye on engine and accessory bearings during maintenance can further help maintain that “freight train” pull without unexpected issues.

Quote
tonychap
Using a cylinder-specific analyzer can help pinpoint which cylinder may be at fault, allowing for a preemptive coil replacement before a full failure occurs, and this targeted approach avoids the frustration of vague fault codes like “AE35 unit.” While ignition components are the usual suspects, it’s also worth remembering that worn Deep Groove Ball bearings in engine accessories or the drivetrain can subtly affect smoothness and responsiveness, so keeping an eye on engine and accessory bearings during maintenance can further help maintain that “freight train” pull without unexpected issues.

While ignition components are often the main cause of idle roughness, worn precision bearings in engine accessories or the drivetrain can also contribute to vibrations and reduced smoothness, so monitoring and maintaining both engine and accessory bearings is important to preserve that strong, consistent “freight train” pull and prevent unexpected performance issues.