Weird power loss
 

My car felt like it was down on power today. As in, its 40-60 time was almost what its 0-60 time should be. It also felt like there was a very, very slight stutter here and there at WOT. There's no CEL though, and the car starts eagerly and idles fine.

It was just at the dealership for the airbag recall this morning. They said what they did wouldn't have affected the engine, though.

My first thought was that maybe the weather was making the engine run hot. It's warm and humid today, fans stayed on after shutdown, etc. But I've definitely driven the car hard when it was hotter out, and I don't remember the car exhibiting these symptoms. Though, thinking of it now, I don't know if the car has seen this combination of hot and wet (hehe) while I've owned it...

Any thoughts? As of now, I'm leaning toward just continuing to drive it and seeing if the problem persists. However, if there's anything I can check myself without an OBD reader, I'd like to do that.

When they disconnected your battery to replace the air bag, it reset all of your fuel trims. It will take it a few drive-cycles to relearn them. Give it an Italian Tune-up (drive the piss out of it) and move on.

Meanwhile, buy a cheap-ass ELM327 bluetooth OBD-II dongle off fleabay and run Torque (paid or free) on your phone.
That way you can see the actual engine temp, as well as myriad other important numbers. Then you'll know if it's really hot or whatever and be ready if you ever do get a CEL.

Will definitely have the Italian tune-up covered. Already go WOT and redline almost every time I drive, and had to do it more than usual with the power loss, lol.

Good call on the OBD dongle though. Been thinking of getting one of those anyway...

Well, after many drive cycles, several Italian tuneups, and around a thousand miles, with another battery disconnect and ESS reset thrown in halfway through for trial purposes, the problem is slightly better but not gone.

Below 6000 RPM and at part throttle, the car feels totally normal. Above 6k, and at WOT, it's... not slower, but not quicker either. It'll still rev to 9k if I'm willing to wait, but I found myself shifting at 6k-7k even when I was trying to move quickly, just because winding it out in lower gears didn't feel any quicker. Misfires are no longer disruptive, but occasionally still detectable (mainly on throttle transitions or when moving between 5k and 8k). There's still no CEL.


Two things I'm wondering:

1. Could the dealership have knocked something loose during the airbag service or "Full Circle" insepction? Disconnected the APV or something?

2. Could I have fouled the spark plugs by driving too hard in muggy weather just after all the fuel trims had been reset?


Any other thoughts would be greatly appreciated!

1. Yes. Check your spark plug wires. I remember now having similar low power with no CEL a few years ago. I took a look after I got beat at a light by a minivan. :shocking: One of my leading wires was completely off. :icon_no2:

2. Don't think so. Italian tuneup would fix that anyway. Wouldn't hurt to pull the plugs and look while you are checking #1, but I doubt they are the problem.

Got it. Thanks, wankelbolt.

Part of me wants to have the dealership do the diagnostics, just so it's on the record if they did screw something up. Then again, another part of me feels like if they did this, I don't want to go back to them. :-P

So the dealership found 54 misfires (spread across both rotors) in the last 10 drive cycles. Definitely something, but not horrible. They really think it was either a bad batch of gas or my ignition stuff, which is about due for replacement anyway. I'm going to replace the plugs, wires, and coils as soon as the kit gets to me from Mazmart, and see what happens.

Just did coils, wires, and plugs.

3 of the 4 coils had white spots, if that means anything. All of the plugs had crusty buildup; uniformly tan on the trailing plugs, black-and-tan on the leading plugs.

Pics below -- rotor 1 in the foreground, rotor 2 in the background:

https://cimg3.ibsrv.net/gimg/www.rx8...e69516b04d.jpg

https://cimg4.ibsrv.net/gimg/www.rx8...0af471a6db.jpg

I drove it immediately after buttoning everything up. It took a few cranks to start back up, but idled fine once it did fire up. I restarted it once after it warmed up; no problem whatsoever there. No CEL at any point. However, the problem with the (relative) sluggishness above 5.5k and the occasional stumble was still there.

Thinking I'll just run it for a few days and see what happens. Any other suggestions?

Generating Power at Full Throttle
• Ignition Coils
• Spark Plugs
• Spark Plug Wires
• Engine Compression
• E-Shaft Sensor (ESS)
• Air Filter
• Intake Valving
• Throttle Body
• Mass Air Flow Sensor (MAF)
• Fuel Pump
• Fuel Injectors
• Catalytic Converter (Cat)

Thanks, gwilliams6.

With ignition out of the way, I guess it's down to:

• Ignition Coils
• Spark Plugs
• Spark Plug Wires
• Engine Compression
• E-Shaft Sensor (ESS)
• Air Filter
• Intake Valving
• Throttle Body
• Mass Air Flow Sensor (MAF)
• Fuel Pump
• Fuel Injectors
• Catalytic Converter (Cat)

So the next question is, which of these could have gone bad suddenly, and/or as a result of a screw-up at the shop?

White spots don't mean anything.
Were the codes only for misfires?
Misfires will often damage cats from dumping unburned fuel into the exhaust that reignites in the cat.
Hesitation at high RPM is a classic symptom of a clogged cat.
P0420 is the usual code for bad cats.
You could change the air filter and check the intake tube for oil, clean the ESS and MAF sensor, reset the NVRAM and see if that helps.

Still not getting any codes. The rate of misfires apparently hasn't yet reached the threshold.

Just got back from my second dealership visit. This time, they said they only found 3 misfires, and only on one rotor. The tech cleared all Mode 6 data and swore the car drove fine.

Then the tech took me for a ride-along and told me, "look, it's getting up to 7,000 RPM just fine." This after I spent probably a total of 10 minutes explaining to various service people that the problem is most noticeable when you go WOT to redline. The service adviser told me nobody felt safe going above 6500 RPM because the pavement was wet. Not sure why it And I've had several conversations with the tech where it took some poking and prodding to get him to admit that he never actually went WOT.

On the plus side, they at least haven't charged me for diagnostics. So there's that.

Ugh.

FWIW, I had the exact same symptoms you encountered when I picked up my car from the body shop in April. For a couple of days, the car was intermittently sluggish at low RPMs, and a few times the engine died while waiting at stoplights. No problems whatsoever at higher revs or higher speeds.

Problem turned out to be what wanklebolt noted: shop's disconnection of battery had reset fuel trims; took a few drive cycles to have car relearn them. Car has been running perfectly ever since. Hope your problems are soon behind you!

That actually sounds like the opposite of what I'm experiencing.

Either way, I'm hoping for the same outcome. It's been like 1500 miles at this point though. :/

Engine Power Loss

chokes as revs increase
O2 sensor failure (too rich)
MAF failure
MAF disconnected
e-shaft sensor fouled
accessory belt fraying
high end power loss (hard fuel cut)
Rev limit reached
high end power loss (jerky and stumbling)
Ignition failure
fuel pressure loss
e-shaft sensor fouled
high end power loss (smooth)
Catalytic converter clog
air filter clog
low end power loss (smooth)
Engine compression loss
low end power loss (stumbles)
Ignition failure
front O2 sensor failure
revs slowly but smoothly
O2 sensor failure (too lean)
catalytic converter clog
air filter clog
sudden power drop at a specific rpm
Intake valving actuation problem
trouble getting to redline
Ignition failure
front O2 sensor failure
catalytic converter clog
air filter clog
e-shaft sensor fouled
fuel pressure loss
MAF failure

I think you said your high end power loss was smooth ,IamFodi. Could be a cat clog or air filter clog, or even an intake valve actuation problem.

Just tried cleaning the MAF. No change.

Tried to get at the ESS from the bottom and couldn't without removing the plastic undertray, which I had trouble doing. Couldn't get a good angle on it from the top, either. Is it in a different location or obstructed differently on the S2? Or did I just not try hard enough?

The ESS bolt is above the sensor itself, so it is easier to unbolt from the top. You'll need to remove the airbox though.

This is where the ESS is on a Series II Renesis.



https://cimg1.ibsrv.net/gimg/www.rx8...180cfbcbca.jpg

Just out of curiosity, the ESS on the S2 has to be removed to be cleaned?
If it does, does it get fouled as easily as an S1?

Some of the later S1 ESS mounts are enclosed like that as well. I'm not sure when that change was made but some are open to the elements and some are enclosed.

Example of S1 covers.

Open:

https://cimg2.ibsrv.net/gimg/www.rx8...2c7b4b89a5.png


Enclosed

https://cimg4.ibsrv.net/gimg/www.rx8...8d1606fea1.png

I'm wondering if it needs to be cleaned as often as an exposed one?
Is a dirty ESS a common occurrence on enclosed ones?
It looks like a PITA if it doesn't need it as often.

Thanks, guys. Really appreciate the help.

9k, those pics are really helpful. If I'm looking at it right, the ESS is in exactly the same location on both the early S1 and the S2; the bracket is a bit different on the S2 to enclose the sensor, but there should be no difference in accessibility. Is that correct?

I did remove the airbox itself, but not the tray under it. Removing those hoses that clip into the brackets at the back of the tray was too much of a PITA and my patience wasn't 100% in the limited time I had. Might try again tomorrow.

On another note, my bluetooth OBD dongle is arriving tomorrow. Any tips on what parameters I should observe/log?

So the car is at JPR Imports now. No word yet, but at least I'm not getting gaslighted by dealership techs any more -- Jim definitely felt the lack of power.

One definitely odd thing we found from driving around with an OBD scanner hooked up: at WOT, the "calculated load" parameter would fluctuate a lot between 80% and 99%. Jim tried the same thing on another RX-8 (thanks, gwilliams6!) and the same parameter just sat at 100% until he let off the gas. Any thoughts?

Also: at idle, it definitely seemed like the driver's side exhaust tip felt like it had more exhaust coming out of it than the passenger's side one did. Is that normal?