What's wrong with cold air intakes, Keith?
What's wrong with cold air intakes, Keith?
From what I understand, the oiled filter on my cold air intake is the reason my MAF sensors kept dying, and the issues brought on by that were very similar if not identical to what eventually could not be rid from the car completely. Now I have a perhaps unwarranted fear of all intake modifications.
Get that weak shit off my track
I think a lot of people go nuts with the oil. If you do it right there really shouldn't be any issues (but definitely still could be). I've had open K&Ns on Saabs since the '90s. Still, now that AEM etc. have dry filters, there isn't much reason to use a K&N anyway. :shrug: Still, given how much work manufacturers put into motors these days, I seriously doubt there is much to be had with an air filter change on most cars. I don't think anybody leaves much on the table anymore.
Cai is for the noise more than anything. Some simple math can prove that.
Oh yeah, I'm no fan of oiled filter elements either. Seen a few MAF sensor elements coated in black goop in my short time messing with cars. This stuff works pretty well for that. But still, I run dry filters when I can.
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So I did some datalogging now that I know a bit more about what to look for. I don't have access to fuel pressure data but MAF voltage seems fairly stable, and the one thing I did recognize as an anomaly is the O2 sensor behavior. The post-cat sensors both show constant 0.28v. The pre-cat sensors differ from each other, however. One goes back and forth from near 0v to near 1v (not quite reaching either). Slowly at idle, more quickly at ~2,000RPM. The other sensor moves from about 0.5v and 1.2v at idle, pretty slowly and with no detectable rhythm. At 2,000RPM it reads about 1.8v to 2.5v. That's Bank 2, which is driver's side if I can assume cylinders 2,4,6 are Bank 2. That's the sensor that had the toasty wire resting on the header.
I inspected the cats before starting the car and they look ok to me. The rear O2 sensors have a black appearance on the sensor element. No buildup.
So I am thinking replace the one O2 sensor and go from there. I'll also ask the PO when they were last replaced, see if I should really do them all ($$$). Worth noting I did hold RPMs around 2200 for 30 seconds to see if readings changed significantly, and once I let the car return to idle the trembling didn't return. Funny.
Last edited by CudaMan; January 25th, 2016 at 04:26 PM.
Here are the cats, looking towards the rear of the car. Left one shows some signs of melting but nothing too bad in my uneducated opinion. Right one looks perfect.
http://www.pbase.com/bryanh/image/162416163/original
You can also see the flatspot in the left one. Darn speedbumps. :x
WBO2 sensors don't behave like NBO2 sensors, they have a more gradual, linear response relative to input rather than bouncing voltages. The 0-1v is suspect IMHO. None of that is normal. The rhythmless one is a *more* normal behavior but still seems a bit off stoich from what I'd expect... IIRC you have an ECM tune so maybe that explains that. If it's not too much of a pain, before spending money you might consider swapping the two and seeing if the behaviors follow them. I don't know what the test is offhand, but you might check the heater circuits (with an ohm meter) - maybe the sensor(s) isn't getting up to temp, and once you've put some heat in it via the exhaust, it starts working better. Hey, at least the steady low voltage on the second sensors mean your cats are healthy!Originally Posted by CudaMan
Hm. Doing some reading, the RevUp VQs were the first ones to get wideband O2 sensors. The early VQ35DEs (like mine) have regular O2 sensors. Also the monitoring software, or the ECU, or whatever controls that readout, labels them "NB-O2 Sensor 1, Bank 2" etc. I think I have narrow-band O2 sensors. They have 4 wires each.
Good info!
Narrowband sensors operate between 0v and 1v, widebands are presented (via ECM) as 0v-5v. If you are seeing anything greater than 1v on a narrowband, something is wrong. I could very well be mistaken, but I don't think narrowband sensors are electrically capable of presenting >1v. So, yeah. something is wrong on that side - it's not an upstream issue.
I think it'd be worth swapping the O2 sensor connectors. It might make the engine a little screwy, but you will be able to see very quickly whether it's the ECM or its side of the harness, or the O2 sensor and its side.
The amount of wires does not denote if they are wide or narrow. the ECM will also not likely say WBO2. Look on the O2 sensors for a part number or something that you might be able to trace down, that will be about the only easy way to tell.
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