Had my header put on yesterday at Midas, helped 'em install it. Rearranged my cat and such too, so that now things are:
header --> downpipe --> flexpipe --> cat --> magnaflow --> piping --> dynomax --> outlets
My primary O2 sensor looked terrible, like it exploded. The shroud around the sensor was frayed to hell, the center part white, and it was also flaking apart. Here's the rundown:
Header
The header is a Pacesetter, JET-HOT coated, made for the Cavalier with EGR. I used a new 2000+ non-EGR gasket for my 2000 LD9 in the Alero.
Primary O2
The header's O2 bung in the collector did not leave enough room for the primary O2 to be installed (wrong side for Alero), so that hole was plugged and the primary O2 was installed in a new bung welded 4-6" downstream from the collector's original bung. The wires were also extended; the gauge of the wire was the same as the stock wires.
Secondary O2
The O2 after the cat was removed, as far as I know it is completely irrelevant, and meant for emissions monitoring only. My catalyst code has been turned off in HPTuners, along with all related downstream O2 codes.
Wideband O2
My AEM wideband O2 sensor is just behind the primary O2, on the opposite side of the downpipe.
The engine idled quite rough at idle after the header install. I noticed it seems to swing to lean quite a bit at idle now as well. I had a feeling the upstream O2 sensor was the culprit, as it had 189,500 miles on it, and looked TERRIBLE. My fuel economy seemed to suck lately as well. Rough idle, wideband spikes to lean when it gets rough, surges while cruising sometime.. all the symptoms of a bad upstream O2 sensor.
So I replaced it today with a brand new one. Absolutely no difference in conditions. Same problem. I figured if a header nut/stud was loose, or if the header collector balljoint and downpipe have a leak, that could cause it. The ball joint is solid, no gaps. Nuts look good on the studs, everything was tightened. No vacuum leaks or disconnected items whatsoever that I can find.
O2 sensor is 4-6" farther from where it is on the Pacesetter. Can that cause this issue? Taking too long for the gases to reach the sensor so it gets delayed response? I can go back and have em drill a hole on the other side of the collector (180* from where the bung that was plugged is) and weld up a bung and try that... Spyhunter's the one who suggested the idea to put it right at the collector where it is at the Pacesetter. Stock location is only like 6" from the head, Pacesetter's is quite a bit farther away, and then this one is 6" from that.
Also, the exhaust is more rumbly now. Sounds like it's getting little bursts of energy every second or so, it thumps. Like... thump thump ..... thump... which may be the effect of having the O2 signal reading a delayed measurement.
Here's an
HPTuners scan from when we started it up the first time and it idled. Any ideas?
So lately everyone's telling me removing the downstream O2 was a dumb idea, and that closed loop uses it... coincidentally the time we removed it was the time the problems began. I didn't think the rear O2 had anything to do with performance, only an SES-light-generator.
@!#$. Gotta call Midas tomorrow and see if they still have my downstream O2 so we can weld in a bung for it and reconnect it. I'm also going to have 'em move the primary O2 to the collector on the side with room.
[ion wrote: C2 .]So lately everyone's telling me removing the downstream O2 was a dumb idea, and that closed loop uses it... coincidentally the time we removed it was the time the problems began. I didn't think the rear O2 had anything to do with performance, only an SES-light-generator.
@!#$. Gotta call Midas tomorrow and see if they still have my downstream O2 so we can weld in a bung for it and reconnect it. I'm also going to have 'em move the primary O2 to the collector on the side with room.
downstream doesn't do jack. I didn't have one on the skwirl for a long time and it ran fine.
I think your upstream O2 is too far down the pipe, you're getting inaccurate O2 readings
same with the wideband
But did you have an O2 sim?
I'll move it up tomorrow.
I was told on a header that pushes the O2 sensor further down needs a 4 wire O2 sensor as it needs to heat up quicker.
There was similar problems only until the car would warm up with the stock O2 sensor.
2003 Sunfire with 2 1/4 inch turbo muffler, 2 1/4 piping, 2 1/2 inch resonator, a 2 1/4 inch catalytic converter, 2 1/2 inch down-pipe, a 4:2:1 RK Sports 'clone' header, E-bay strut brace, ground wire kit and an AEM true cold air intake NOPI edition.
[ion wrote: C2 .]But did you have an O2 sim?
I'll move it up tomorrow.
no. I unplugged the sensor, taped up the connector, and disabled it in HPT.
and just as an aside, the jbody sensors are 4 wire
The rear O2 is a 4 wire on mine. So I guess I don't need to hook it back up then... that's the only thing that really changed besides the upstream O2 sensor location.
So if I weld a bung right at the collector and put the upstream O2 in that, should run fine? Hoping that fixes it... not much else I can think of.. :/
the location of the primary has to be it.
whats the total distance along the piping of the header that the exhaust has to travel before it hits the sensor?
what style header do you have?
Had problems with my stock non heated o2 sensor not heating up after my header install with stock piping. Got the exhaust done and was even worse. Put a heated 4 wire be a matter fact the one after the cat in and wired it up and been fine since. Thise also on a 2000 2.4 in a 99 fire.
It's a Pacesetter 4-1. The bung it came with is plugged and a new one is put in the downpipe.
sure there is no problem with that EGR??
I dunno I thought most people used ones with EGR just had the tube blocked off by the 2000+ gasket (engine is a 2000).
Today we're putting the rear O2 back in for the hell of it, and moving the upstream O2 closer to the head. Should I put it in the collector (albeit on the other side) as the Pacesetter's original one was, or put it in a runner? The collector I'd think would be the best spot.
Should I have them cut the tube off and weld the hole in the runner?
Blown Phoniex wrote:Had problems with my stock non heated o2 sensor not heating up after my header install with stock piping. Got the exhaust done and was even worse. Put a heated 4 wire be a matter fact the one after the cat in and wired it up and been fine since. Thise also on a 2000 2.4 in a 99 fire.
i would try a 4 wire fist ive heard of people having to do that and if you could just reuse your downstream o2 why not try it
Did you have the EGR deleted BEFORE this header install???
John Benham wrote:Did you have the EGR deleted BEFORE this header install???
I don't have EGR in the first place. I have a 2000. I bought a 1999 EGR header. I thought that the little tube may be causing a leak pre-O2 by exhaust gases pressing against the gasket on the other side of the tube that comes out of the 4th runner.
mikieb510 wrote:Blown Phoniex wrote:Had problems with my stock non heated o2 sensor not heating up after my header install with stock piping. Got the exhaust done and was even worse. Put a heated 4 wire be a matter fact the one after the cat in and wired it up and been fine since. Thise also on a 2000 2.4 in a 99 fire.
i would try a 4 wire fist ive heard of people having to do that and if you could just reuse your downstream o2 why not try it
I don't see why a 4 wire would solve things, the problem isn't that it's not "heating up" properly. It goes into closed loop, it switches, it functions. The exhaust worked fine with the 2 wire before the header install. And now there's a brand new upstream O2 in there.
I think it's just delayed or that there's an exhaust leak in the collector ball joint or at the head somehow.
i had a similar issue. i swapped headers and since i had the original o2, i figured i would change it. it ran like crap and stumbled.
my problem ended up being the actual brand of O2. i bought a bosch and switched to ac delco. problem solved. you also have the problem of being too far downstream. you need either a 4 wire O2 or put a new bung in on of the primaries. both my RKS and the DC header have the O2 in just one of the primaries, and I have no problems.
You sure about having it in the primary? I can put it in the collector or the primary. In the primary it'd be as close as possible to the OEM location, but it wouldn't be getting the reading from all the runners. I also replaced it with a BOSCH sensor.... hmm..
On GAGT everyone's talking about how BOSCH sensors are garbage and cause these kinds of problems... but this problem existed before I replaced the OEM, which leads me to believe it's not the O2 sensor itself, but some other physical problem such as the location.
http://www.gaownersclub.com/forum/showthread.php?t=97623
From other automotive forums:
Quote:
Something everyone seems to overlook when talking about that rear O2 is that it DOES affect your fuel trim, aside from monitoring the converter.
And the reason the measurement is inaccurate the farther you go away from the head on the upstream O2 is
Quote:
Further from the chamber, the reaction is more complete.
Says the tune is made for the OEM O2 placement.
Should I put it in one runner (closest to OEM location) or in the collector?
[ion wrote: C2 .]John Benham wrote:Did you have the EGR deleted BEFORE this header install???
I don't have EGR in the first place. I have a 2000. I bought a 1999 EGR header. I thought that the little tube may be causing a leak pre-O2 by exhaust gases pressing against the gasket on the other side of the tube that comes out of the 4th runner.
ah, I was confused, I thought you put a 00 engine in a 99 car.
I would avoid putting it into 1 runner, as then you would only be sampling gasses from 1 cyl.
I would say put it in the collector as close to the motor as possible.
Will do, along with reinstalling the rear O2.
Going over my logs with pre-header and after the new sensor, it seems like the new sensor switches a LOT faster than the old sensor that looked like garbage. The short term fuel trims stick closer to 0 too. From the data it seems like it should be running better, not worse. Could it be that I just need to re-tune my VE?
I'm trying everything today. Moving O2 to collector, reinstalling rear O2, having the two butt splice connectors on O2 soldered instead.
whatever you do, just make sure you get rid of the bosch, although you still might have problems with the o2 not getting up to temp quick enough.
It takes a while to get into closed loop but that's not my damn problem. It's that it runs rough. The problem existed with the old GM sensor, it's not that it's a BOSCH. The new BOSCH one works quite well, reads extremely quick and the logs look good.
We couldn't move the upstream O2 any closer, not enough room to weld, and we weren't gonna pullin the header off, or put it on only one of the runners, bad idea.
Welded a bung behind the cat and put in the rear O2 and reconnected it. Also soldered the upstream O2 connections for the wire extension instead of the butt splices. Still no difference. Maybe it just needs a tune now. What I find odd is the idle O2/fuel graph:
Cruise
Idle
I'd get the rear sensor out of your head! Seems your main concern when it shouldn't be at all. All 3 of my cars haven't had the rear, I only used the sims to disable the CEL which your HPT has done.
This is something else.
I personally would of kept the 1st sensor in the collector and mocked it before install, the downpipe is a good stretch for it.
