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I'm stumped.. (intermittent issue) O2 sensor makes a VERY rich condition

I've just reconnected a new O2 sensor into my GHL headers. After a little warming up, I took her out for a stroll... and it was acting strange the first 5 minutes, seemed like it needed to warm up. The car would not idle right, and almost died when at a stop light (idle at 200 RPM). When all that was out of the way, the car ran fine.

I stopped the car for 15 minutes.

When I started it again and went all, the first chance I got I nailed the throttle to get a good rush of boost.. but the just wanted to cough and die.. I immediately looked out the rear-view mirror and there's a big black cloud of smoke out the rear.

I try gradually pressing the throttle, and again, it bogs and just dies. It seems to be when I start to hit boost.

10 minutes into that drive, I try again, all works fine??

This whole problem started when I replaced my GHL headers last year. I heated my O2 sensor cherry red to get it out... turns out that wasn't good, so I bought a new one, and it was good for about a month.. then the issue started again. When I disconnect the O2 sensor, the problem goes away.

Some questions I have..

1.Can't be the new sensor can it? (2nd one)
2.Can it be an exhaust leak at the headers?
3.Is the O2 sensor somehow connected to the WUR, and maybe the boost signal spikes too soon, telling the WUR to dump more fuel?
4. Can it be that fuel enrichment box (that thing under the seat)? If so, how do I check it?
5.Could it be that the way I wired in the O2 sensor, that the wires are too close to the engine and the heat is causing some havoc?
5. Is the relay under the drivers seat for this.. maybe a connection?
6. Is it Ignition that is somehow conected to the O2 sensor, and it doesn't advance when the RPM's rise?
7.Could it be my throttle position switch?

I mention the exhaust leak because I think the drivers side headers seem to be pfut pfut pfut pfut pfuting... so I tightened up the exhaust bolts when I got home.
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1987 930
1956 Chevy 3100
2009 Subaru Forester
2003 KX250 X2(I like my toys!!)

Last edited by mark '87 930; 03-30-2007 at 06:25 AM..
Old 03-29-2007, 05:04 PM
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I don't have a CIS based car, so I can't really help much, but if the engine performs fine without the O2 sensor, then why not just leave it disconnected? Are you reconnecting it for the smog test police?

On my Motronic based motor, I left the O2 sensor disconnected as I found the car performs better without an O2 sensor. Albeit, a bit richer at idle and part throttle, but certainly performs better. With the O2 sesnor in, the ECU makes the idle/part throttle mixture leaner, for better economy and emmissions. I prefer it on the richer side, even if it means fuel economy suffers a bit.
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Merv
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Old 03-29-2007, 06:32 PM
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Merv,

I know it's taboo to speak of being fuel economic... but much of my driving is done around town unfortunately..so that's why I wanted it connected. Also, I used to find that the with the O2 sensor connected, the performace was much crisper at low RPM's.

I'll see if anyone else chimes in and can point me to anything.
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1987 930
1956 Chevy 3100
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Old 03-30-2007, 03:54 AM
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If you disconnect the o2 sensor, what happens? Does it go back to normal? To me it sounds like a wicked boost leak or a bad warm up regulater. On my old cis car, the wur went bad and it made it run verrry rich, it was hard to even get on the gas without it stalling, but if i got the rpms up and beat it the car would boost.
Also, whoever disconnected the o2 sensor, is it possible that they made adjustments to the CIS adjustment in order to richen it out?
As far as the exhaust goes, you may have to tighten it a few more times until she complies.
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Old 03-30-2007, 07:35 AM
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the O2 sensor was connected before I had the GHL header system.. and there were no issues. I know for a fact that nothing has been changed other than that. You mention stalling, and that is more the word I should have used, as that is what it feels like.

If I disconnect the O2 sensor, all goes back to normal.
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Old 03-30-2007, 07:55 AM
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Then maybe the warm up injector in the back of the motor is stuck open? If not that, it may be a control problem. I have a stock control unit around my house somewhere if you would be interested in trying. I have that as well as all of the relays from under the seat.
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Old 03-30-2007, 08:00 AM
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By warm up injector, you mean the CSV(Cold start valve)? I didn't think that was tied to the O2 circuit.

I'd be willing to try that (stock stuff to see if that fixes the issue). We can discuss the details of that offline if you like (mark.thoun@telus.com). It at least gives me a base for troubleshooting.
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Old 03-30-2007, 08:06 AM
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I had the same problem on mine but it ended up being a faulty Andial FE system. Atleast the problem seemed to be solved by disconnecting the FE at the frequency valve in my case....

Unfortunately it doesn't appear as though you are running a similar set up.
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Old 03-30-2007, 09:50 AM
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No aftermarket FE for me, but I wonder if the frequency valve can be suspect? Although, it works fine when I disconnect the O2 sensor? I am really at a loss with this one.
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1987 930
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Old 03-30-2007, 09:56 AM
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The cold start valve circut is not conected to the o2 directly. The o2 sends a rough exhaust gas temp signal to the computer to let it know that it has warmed up (in combination with the other million temp sensors around the motor) and in turn the computer stops the cold start valve from delivering fuel. I know you dont want to do this, but when I had my cis setup i had nothing except for an msd box and two fuel pumps running the motor and that was it. I know you want all of the stuff so it is more driveable.
Now maybe we are missing something here, is the o2 location the same on the ghl headers? maybe you might need to adjust something becuase it may be changing the temp. at the o2 sensor
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Old 03-30-2007, 10:01 AM
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That is a good point, the O2 sensor is MUCh closer to the turbo in the GHL application due to the fact that the headers as so much shorter that the stock ones.. That could certianly be a cause, but I can't conrim that. I wonder if anyone is running their O2 sensors with a set of GHL headers and all is well?

I was giving this additional thought, I'm going to check the throttle position sensor/switch. I don't know where it is, but I am going to check that. I wonder if the switch is not working properlly, it would cause the O2 sesnor to remain in the loop at WOT, and it should not.
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Old 03-30-2007, 10:36 AM
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The TPS is right on the throttle body on the passenger side. In order to get to it you may have to remove the air intake (Im not sure as it has been sooooo long since I have worked on a car with a stock intake).
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Old 03-30-2007, 12:29 PM
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You may have an intermittent ground on your O2 sensor
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Old 03-31-2007, 10:44 PM
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The PO had the O2 sensor disconnected intentionally, on the advice of his mechanic after a top end rebuild and some upgrades. I have left it that way and my mechanis agrees. Don't lots of us with upgrade, turbos, exhaust, etc. run without it???
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Old 04-01-2007, 07:58 AM
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