Extreme power loss, rough idle. Help!
 

I drive an 03 350z Touring, and a few days ago it did a small jerk while cruising on the highway, I figured it was because of the -2 degree weather. No other symptoms until yesterday driving to work it acted completely bogged down when taking off. Had trouble just revving it up to 3k to get going. Then it would straighten out for awhile, and then back to being sputtery. At times it almost seemed jumpy. At the stop light the idle would fluctuate, then rev up and normalize. The SES came on, but kept saying rear bank 2 02 sensor, as I have test pipes. Only mods are the test pipes, aem cai, and catback exhaust. I have no idea what's going on! Please help a brotha :/

Check your MAF sensor.

Try a little dry gas.

Did you get a tune after you added those mods?
Your car is prolly running lean,thats one thing.Also,
I'd check your cam position sensors.

Ethan,

You need to get the codes, but I’ll bet (I’m very certain) you need to replace your crankshaft and/or camshaft sensors. If your 2003 Z has more than 80K miles, it’s for sure that you need to replace some sensors. I recommend replacing both banks of both sensors. That saves $$’s later on avoiding a piecemeal repair.

You might throw a code for the O2 sensor, but wait on this until you replace the other sensors (which might fix the O2 code).

Your TPS and Throttle Body are probably OK. It’s possible to test the TPS with a multimeter. If the TPS tests as faulty, you should attempt adjusting it. If you cannot adjust the TPS, you need to replace the entire Throttle Body.

--Spike

As of now it's sitting at only a little over 43k miles, I changed the plugs, and cleaned the MAF sensor thoroughly. Took it for a short drive and it seemed good, the drive to work and back on Monday should tell for sure :) I appreciate all of you helping though! If this isn't solved the camshaft sensors are next on my list.

So you didn't try a little dry gas? That would be my first guess on a -2° day.
You B2-S2 code is obviously due to the lack of catalytic converters, since the downstream sensors' primary function is to compare readings before and after the cats.
You'd be a fool not to add some dry gas and eliminate that possibility all together.

EthanF is no fool (as you suggest) for not trying “dry gas.”

Actually, Ethan has already solved the problem, and the fix never required your “dry gas.” advice.

Yeah well dry gas has solved issues like this before. Always start with the obvious things first.

What was the fix? Haven't heard for sure yet have we?

Apparently the fix was not "dry gas."

We still don't know the problem is fixed though do we, as post #6 would indicate.

You guys....plz dnt fight! :( Anyways, I've driven about 130 miles since the last post and it seem to be running good!!! Still have the stupid SES light form that darn 02 sensor though haha, even after 2 resets. I wonder if dry gas might not be a bad idea anyways just in case there is a little condensation?

^^ We are not fighting... we are debating, and we are presenting different ideas/solutions/answers. It's all in fun and what makes these forums interesting.

It would be boring if everyone was super-polite and there was no controversy whatsoever.

--Spike

Spike, that is the smartest thing you've said since I came back here, I have to agree with you :)

Again with the dry gas, what have you got to lose? A bottle of iso-heet is like 2 bucks. If it were me, I would have to know that possibility is ruled out. I've had cars freeze up before and it's not fun. They usually do it when they get below half a tank in super cold weather.

it never hurts, especially being in minneSNOWta... gets damn cold there... so glad me and the ex didnt work out because i would have to move there....i like my mild texas winters

I had a funny idle in my g and I cleaned the throttle body and it was good. I just put a spacer in my z and cleaned the tb just cause. The z was way dirtier with way less miles and wasn't giving any idle probs. anyways it's clean now. Tb gasket is 5$, sometimes it's cheap fixes that we overlook. Clean engine= happy engine

Well poop on my chest, the problem has returned! Again for a split second while accelerating in 3rd it seemed to have trouble until it got above 3k rpms. And yet again, the weather was about -3 below zero. Next step is dry gas, and cleaning the throttle body! I'm going to attempt doing that without removing it as I'm worried about damaging something hahah. I really hope this thread ends in me with a fixed car, and a solution for someone to fix theirs in the future :P

On a side note: this is the first winter this car has ever been driven in the 11 years of it's existence, and I do have 17 inch winter wheels in place of the stock 18's. I don't suppose this could be messing with the VDC?

If you have vdc, the wheel and tire size doesn't really matter. What does matter is the diameter difference. They can be the same size, or "square", but they can't be more than about 3/4" different from front to back.
I'm sure someone has the exact difference in circumference all figured out somewhere.

EDIT, make sure your throttle body hasn't had a coolant bypass done to it.

Ethan... What are your tire sizes? --Spike

Right now I'm running 225/55's on my 17's all around so I don't think that can be it. And to add to the confusion after driving to the gas station and filling up before the dry gas, it wouldn't start!!! After a quick jump from a nice old man it fired right up, but still threw me off how that happened...

^^ Your tire sizes are good. --Spike

Yeah no reason to suspect a tire issue, as long as the tires are the same size or the rears are slightly larger.

So all was good until today in -10 degree weather it bogged down, gave me a SES which read as both front 02 sensors. Cleared the codes, reset the cry and it was perfect the rest of the way home. WHAT THE EFF?!?! If they were truly the problem it should still have issues after the reset, no? I'm beginning to think my car just doesn't like the cold....

The ecu reset will reset the rediness monitors, which means it may not detect a problem right away. both O2 sensors throwing codes, I would look for a lean condition being caused by something.

And finally I have some codes to work with!!! P0321, P0152, P0300, and P0158! Which if I'm getting this right is that I have a misfire! Not sure where to go from here...possibly a bad coil pack/injector? :/

Random misfires are most likely to be caused by a fuel delivery issue, but there are many other possibilities.

Cleaned the (very dirty) throttle body today, did all the resets and got the readings off of the front O2 sensors....both read 1.3 volts!!!! If I'm not mistaken that's really really rich :/ Now I'm even more confused

Did you let it warm up and go into closed loop before you took the readings?

Yep! Even while cruising on the highway it was a pretty steady reading of 1.3v from the sensors

That sucks. FYI, if you have a coil pack issue your check engine light will flash. I think I'd dismiss that possibility for now.

Swapped maf sensors with a friend today....still rough idle and still the ses light comes on showing both o2 sensors are reading high voltage. Could they booth be the root of my problem? I'm running out of ideas :(

And the 03003 misfire I should add too :P

What are the rear O2 sensors reading? I have a sensor getting bad on my truck, the fuel trims are even, rear sensors are even, one upstream sensor reads a bit high. Fortunately, it's still within it's range and there's no worries at this time.

both upstream sensors are reading a pretty steady 1.3v

And the downstream sensors?

Maybe you should check if all plugs are firing. It could be just bad coilpacks.
I had dead coilpacks before and it made the car idle rough and lost a huge amount of power. It also caused CEL and a few other errors to show up.

Downstream sensors are also reading 1.3v due to test pipes I'm assuming. Coils should be good if I checked them right

Ok, all of your sensors are reading 1.3v correct? Your car is extremely rich. I don't believe they can go past 1.3v, but I may be mistaken there.

I would also rule out the misfiring completely, since running extremely rich will cause the ecu to detect a misfire. Something is causing this car to dump fuel, and I'm thinking it's intermittent as well.

Yes, a solid 1.3v on all four O2s. Occasionally on a cold start it'll try to drop down to a normal fuel level, stutter, and then rise back up to 1.3v. And then stays there wether I'm accelerating or just cruising. Very very odd and confusing. Just threw a P1164 code today as well

That code says O2 sensors all the way, but of course it could be wiring. The steady 1.3v says it's running well beyond the range of the sensors, which is rich enough to cause all the power loss, misfiring, and rough idling.

I'd hate to say you need at least 2 new sensors, but from my computer desk that's the best I can do.....and then I have to wonder what could've caused this issue.

I kept thinking that was it lately! Took it to the shop today where he can read each wire and possibly find a bad ground? Hopefully he'll get to the bottom of this :/

I have an 03 w/ no mods and had the same symptoms as you w/ the p0300 random misfire code. Turned out to be a bad coil for me. Problem started slowly and was intermittent, a year or 2 later it kept getting worse. Kicking myself that I didn't test the coils sooner (disconnect one at a time to see which one made no difference). Hope this helps.

FIXED! Here's the follow up: took it into the shop, both front oxygen sensors were reading out of spec. Replaced them, better, but it still did it. Replaced one of my other after-cat oxygen sensors FIXED. All three O2 sensors, AND my maf sensor went bad at the same time!!! Who would've guessed....just happy it's all good now :)

That's good to hear. Hopefully it stays fixed, because something caused those sensors to fail.....And that something was probably the MAF.