Hey guys. A couple weeks back My idle started bouncing up and down(surging). I checked under the car to notice that I had a cracked frontpipe. So I had it welded. THe next day I launched the car and it started surging again. I found out it cracked the other half. Yesterday I had a flex pipe added between the collector and o2 sensor to absorb the vibration to prevent cracking. Once I got it home, I took off the pos cable to reset the computer. I let it idle for about 30 minutes and it idled fine. I drove it home at about 60mph on cruise. Ran just fine. Got off the hi-way and it was idling a bit higher than normal, but I thought nothing of it.

My question is... Does the computer need to relearn a fuel map because of the couple hundred miles I drove with surging o2's due to the leak between the motor and o2 sensor? And if so, how long does it take to relearn itself?

Any ideas or other things to check?

Thanks,

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~Joe - aka spider gear destroyer
'94 Stealth R/T
-Lightly Modded ;)

Yes. Reset the ECU again. You need to leave the pos cable off for a while inorder to completely reset it.

I've heard/read mixed things about how long it takes the ECU to adjust to different situations so I can't comment on that. (pulls out CD manual)

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06 Blue EVO 9

I had the pos cable off for a good 2+ hours. I took my buddy's car, worked out, then went out for a couple drinks and dinner. So It was probably closer to 3 hours. ANd I just went under the car and didnt see any exhaust cracks or feel any air leaking out anywhere, but I do hear a slight leak when the engine surges up and releases. But nothing more than a little gasket leak sound.

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~Joe - aka spider gear destroyer
'94 Stealth R/T
-Lightly Modded ;)

That will be enough to cause a problem. The issue is, the exhaust velocity is so low at idel, it takes the easiest way out (which would be the hole in the gasket). One side of the motor has less back pressure than the other which leads to a number of anoyances.

I've had gasket leaks in my testpipe before and never a problem.

Its after the o2 sensor, so it should cause the o2's to surge like that.
I'll try resetting the ECU again for another hour or so. See if that helps. I'll also go back underneath and check the exhaust now that it is cold for any leaks.

Thanks for all the help. I'll keep you posted.

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~Joe - aka spider gear destroyer
'94 Stealth R/T
-Lightly Modded ;)

Well just went back under the car and started it up now that the exhaust is cool and I could get my hands all the way around it without the chance of 3rd degree burns. And yes, the lazy-ass at the exhaust shop, who insisted that there is enough room for him to weld that new section of pipe in with the downpipe on hte car, didnt get the weld around the top of both ends of the new pipe. This is the type of shit that pisses me off. So tomorrow morning i'm going back down there and watching him remove the pipe, clean up the crappy weld job he did on it, put a new clean weld completely around it, and make sure he puts all new gaskets on(which I gave him to put on and he said he didnt need). ARGH!!!

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~Joe - aka spider gear destroyer
'94 Stealth R/T
-Lightly Modded ;)

Give him hell.

Going back to the leaky test pipe gasket. That leak was too far back in the system to make a difference. Leaks in the manifolds or O2 housings will lead to headaches.

Right Jason?

Yeah, thats what I was saying. But now that I know the problem, I will make sure its taken care of tomorrow morning.

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~Joe - aka spider gear destroyer
'94 Stealth R/T
-Lightly Modded ;)

Where are you having it welded, so I can avoid that shop when I have my DP fixed?

The ECU should be reset after 1-15 minutes without power.

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1992 3000GT VR-4
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3SI Member 0660, 1753, 2038
W3SI Member 15

I had it welded at th meineke on 188th and bluemound rd because I know the owner. But I'm pretty sure his lazy son pawned this job off on someone else after I left and they didnt have a clue what was to be done or anything. Because I've never had a problem with any work I've had done there in the past. And I will continue to go there because this was probably an honest mistake and I pay next to nothing for the work I get done. Either way, this pissed me off and someone will hear about it tomorrow.

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~Joe - aka spider gear destroyer
'94 Stealth R/T
-Lightly Modded ;)

Yeah, I know what you mean! I have a crack in my front exhaust manifold and sometimes I get some idle surge. It depends on temp and such.

Yeah, sucks, doesnt it.
Now imagine driving all the time like that. My crack is within 10 inches of my o2 sensor. It surges constantly. Very annoying having to ride the clutch and brake all the time at the lights to keep it from running 3 grand and being too loud.

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~Joe - aka spider gear destroyer
'94 Stealth R/T
-Lightly Modded ;)

Well I just got home from the shop. Exhaust is 100% leakfree from the motor all the way to the tailpipes. I took off the pos cable for about 25 minutes. Car stil surged ike it did before all the way home, but I didnt notice(or hear) any leaks. All the noise came out the tailpipes. So lets just hope after a few warm-up cycles the computer learns a clean fuel map again. If it doesnt, any ideas what else could cause this?
Thanks,

_________________
~Joe - aka spider gear destroyer
'94 Stealth R/T
-Lightly Modded ;)

I'd like to hook my datalogger up to your car sometime. Got a feeling you're looking at a dieing ISC. Believe there is a way to test it in the manual.

Did you pull off the coolant lines to the throttle body?

Read this thread.

http://www.us3s.com/freeforum/showthrea ... eadid=2379

Test proceedures for the IAC and a place with rebuilt units

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1992 3000GT VR-4
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3SI Member 0660, 1753, 2038
W3SI Member 15