I'm still getting the check engine light every 50-100 miles since having a clutch install that required the removal of my LT headers. The DIC posts codes P1134 and 0133 which point to the front left bank O2 sensor as the culprit. I have brought this to the attention of the installer who has switched out that O2 sensor twice, but the problem keeps returning. He has inferred that the computer programming is possibly to blame, but that hasn't been change for several years. A friend has suggested that an air leak may be the problem, but my installer has checked the headers for a leak and can find none. Does anyone have any suggestions? Thanks.

 

Check the heater fuse for the O2 sensor and inspect the wiring for and knicks, cuts, or frays.

 

Thanks for the suggestion, but the fuse and wires all check out ok.

It seems that the codes return after the car goes into a closed loop for a variable period of time. On a handheld scanner, the sensor never drops down to a low enough level (it appears to continue to try to correct a lean problem).

The installer removed the intake manifold to reattach an AC vacuum line (the AC system is not working either), and it's been suggested to me that maybe some air is leaking in because the gasket was not changed.

Any thoughts?


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Mike

 

I would think a vacuum leak would set a P0172 as well. Can you monitor your fuel trims with the scanner you have? O2's just don't die like this, something else must have happened. Did he torque the intake to the correct values? If there are not obvious leaks in the exhaust and you have installed a known good O2, think it might be worth looking at the intake. Get some brake cleaner, spray it around the intake while idling, see if the RPM changes.

 

No P0172 codes and I can't scan the fuel trims. I don't know if he torqued the intake correctly, but he's changed the sensor twice and the problem comes back within 200 miles of a new sensor. He swears that the exhaust has no leaks and has had the car several times without charging me any extra. He wants to blame the programming as a possibility, but it seems odd that even with all of my mods (which I've had for years), the problem only started after the clutch install.

I'll try the brake cleaner suggestion, thanks.

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Mike

 

This can be an ongoing problem with headers, exhaust leaks and "cold" 02 sensors.
First you need to check you fuel trims somehow and transpose the 02 sensors to see if the problem goes to the other side. I suspect you have a heavy + LTFT on the driver's side front 02. If so the answer lies in finding the cause of the leak. It does not take much of an exhaust leak to set this code especially with headers.?

http://www.gearchatter.com/viewtopic10054.php

 

Thanks and I agree with what you're saying. In my gut, I can't get passed that there must be an exhaust leak associated with rebolting up the headers. But, the installer that did the clutch swears that he changed the gasket when he refit the headers and he's had the car back twice now on a lift and can't find any evidence of a leak.

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Mike

 

Both of your codes point to a lazy functioning 02 sensor. The PCM expects to see it transition so many times across the threshold voltage in a certain amount of time. If it doesn't, these codes get set. Since you're only getting codes for one sensor your fuse would not be the problem. Swapping sensors side to side should verify that it's the sensor but having a scan tool would probably save you some time. For some reason 02 sensors don't like being removed and reinstalled sometimes as I've found out. Maybe a question of sensitivity.

 

As you mentioned, the sensor doesn't transition like it should when hooked up to the scan tool. It never cycles low enough like it should, but I'm having difficulty believing that the 2nd replaced sensor has gone bad as well.


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Mike

 

Look directly below the master cylinder on top of the frame and you will see a small single ground stud with a braded wire. That ground stud is the ground for the heated O2 sensor. The ground wire also connects to the drivers side of the engine block. I would soak that stud in WD-40, remove the nut, clean the connections and see if that solves that problem.

BC

 

Good call Bill. Ground issues can cause all kinds of electrical problems...... especially with these cars. Check the basics.

 

Bill,

Thanks for the tip. I will try this when I get back from a trip on Sunday. I hope that you are right. Thanks again in advance.

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Mike

 

I went through 3 Bosch O2s before I got a good one.

 

Run a can of Seafoam thru the engine. The smoke will show if/where there are system leaks....

 

I have had the P1134 (driver side) and P1135 (pass. side) codes ever since my header install a couple of months ago. Funny deal, I was running a brand new LC-1 as a narrowband on the pass. side, so I know that the sensor wasn't bad. I am also positive that there are no exhaust leaks; I have checked several times. Good idea on checking grounds and fuses, etc.

The codes haven't really bother me, though, since the car runs fine, and I went ahead and turned those codes off anyways, and am now running open loop speed density, thanks to EFILive.

By the way, nice Z!

 

Thanks again, everyone.

Will check the grounds and run some tests for leaks as soon as I can.

The codes bug me because I hate seeing that damn check engine light every week.

It's just the front left sensor, but it still bugs me.


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Mike

 

You will save yourself lots of effort in the long run if swap the 02s L<>R after you check the grounds. If the problem moves you have your answer.

 

Well, I checked the ground screw and everything looked buttoned down. I cleaned it anyway.

I also sprayed some brake cleaner around the intake. When I sprayed into the valleys, the RPM's bumped up one or two hundred, then settled down and would not budge again with more spray.

I can't easily switch the the sensors, as I don't have access to a lift, but I'll wait and see if the situation comes back again.

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Mike