i have a 93 trans am with JBA headers and Y-pipe, hollow cat, 3" pipe. i get the code weather i have the muffler on or off. i have had this problem for as long as i can remeber. started long, long after cat was hollowed and after 1str set of headers and a good while after the JBAs went on.

Here's the problem. the check engine light usually does not come on driving around town. at least then i am frequently change rate of speed. nor does it come when in traffic idling. when is does come on is most commonly on the highway when i am traveling a the same rate of speed for a while. it will usually come on anywhere from 3-10 minutes after i settle to a steady speed.

i tried putting on new sensors and it happen on the way back to the store to get my money back on the ones that went bad. or i thought they were bad.

factors that might contribute to this ploblem. the headers are wrapped. i have also heard that a bad EGR can can cause this as well. i plan on loosing the ERG and AIR systems when ever i get the time. will this cause more coeds to come up? some people have suggested going to a heated O2 sensor since i am running a 1 wire sensor. i figure with headers wrapped the EGT would be plenty high and i would not need a heated sensor.

don't know if this is causing any loss of power but i have been told that this will cause the system to stay in an "open loop". don't know what that means or why it may not be good.

 

Exactly which code is it? What are your other mods? any header gasket or other exhaust leak? Coated headers or uncoated?

 

i think that it is a code 16. its been a while since i checked it. MSD 6AL and coil, Hypertech Thermomaster chip w/ 160* stat, Mac under drive pulley, 4:10s, hurst shifter, functional ram air hood, throttle body by pass, centerforce clutch, A/C delete (just recently though). these are all the mechanical add ons.
i do have some gasket leaks in the colletors but the header gaskets should bee good and i have som pine hole leaks in the weld joints.
headers are coated inside and out. yes i have heard it is bad to wrap coated headers but no thought to tell me untill after they were installed. it does help keep under hood temps down quite a bit while driving and cuts back a little on thermal soak while she sits. after putting the new headers on i drove about an hour from scool to my job. when i parked her i was able to open the hood place my hand directly on the intake and hold there for as long as i wanted. i was pleased with those resolts.

 

here are some thoughts.

Check the codes again once more to be sure that there is still only one. 16 isn't an 02 code. 13 maybe? Check on that for me. It will help to find an answer and to see if that is the only one set. Once I know that I can go from there. I have about 5 different things that I can sugest at that point

 

i will check it by the weekend.

 

If you're sure the problem is O2 related, then I would bet the collector leaks and the weld leaks is the problem. Couple that with the less accurate 1 wire sensor and it's gonna send some bad data back to the PCM. That's my bet. Fix your leaks and see if the code still throws. Also, open loop fueling is based on specified AFR targets in the PCM vs. your manifold pressures and does not use the O2's for data. Closed loop operation uses O2's for fueling data. I love the way your car looks, btw. What wheels are those?

 

they are a cheaper version of the Welds that i really wanted. the Welds were over $400.00 a pop. These are from Ultra and were just over $200.00 a pop. they look real nice when polished but need to be polished about every 2-3 months. the aluminum used is not as high a quality as the Welds of course. i am getting the Mother's power ball for fathers day so that should help. moral of the storey: if ya got the money get the better wheels. i just have always loved that billet look. thanks for the compliment.

 

First thing to do is reset the EMC and then drive the car, get new codes set and then pull them. Pull the fuse for the ECM out overnight, then drive the car and see if the codes come back.

Since the car is a 93 you can pull the codes with a paper clip if you don't have access to a scanner:

With the key OFF, and 1/2 a paper clip bent into a U, insert one end into the top row far right right port on the ALDL, and other end into the top row second port. ports A+B

Turn the key to the ON position ( not start ) and you will hear the fans come on and the SES light will start flashing:

the SES will then flash a sequence, 1 Flash (Pause) Flash Flash (Long Pause), it will do this two or three times to denote a 12 which is the diagnostic mode.

After that is will begin flashing the trouble codes ie a 1 flash (pause ) Flash Flash Flash Flash Flash Flash ( long pause ) would be a code 16.

Flash Flash Flash Flash (Pause) Flash Flash Flash Flash Flash Flash Long Pause three times. a code 46

Write down the codes the ECM has stored.

Once all the codes have been flashed, the computer will continually flash DTC 12s again. At this point you can turn the Key OFF and remove the paperclip.

If I recall O2 codes are 40s- right bank and 60s- left bank. 43/63 lean, 44/64 fault and 44/64 rich. not 100% sure, I'll double check.

A code 16 is for the opti resolution = opti going bad!

But if it is a O2 code, check that the wires going to the O2's haven't melted by touching a header, then will cause the ECM fits too.

 

Have you removed your cats?

 

i was going by the free-be book that autozone hands out with the code keys. i will recheck the code and check my haynes manual to see what it lable that number as.

 

Here is a link that you can use

http://shbox.com/1/Dtcs.htm

If you plan on keeping the car you might want to look into better scanning software. With our 93s we can't use a selfcontained scanner like scanmaster, or some other scanning tools the 94+ plus car can use. I have DIACOM and TTS software to scan my car, both are for PC/Laptop.

Diacom isn't cheap, but it can scan all ODB I GM cars and comes with the cable.

TTS is free for 20 recordings. But it is only for 93 LT1 cars and you need to by the cable.
http://www.ttspowersystems.com/index.htm

So both have advantages, I perfer the TTS because of the way it does data logging and playback.

 

Quote:

Originally Posted by WS6T/A98

Have you removed your cats?

they were hollow many moons ago when i put the custom exhaust on. my factoy muffler sounded like a baby rattle from all the cat guts in it. i never had to hollow it out myslef it did it on it's own.

 

i didn't get very far when i went to get the code again. i have to drive on the highway to get the code that i am pritty sure is for the O2 sensor. i barley got out of the driveway and the check engine light came on. but it was not the code i was looking for. i got a 36 and that means i have to replace my OPTI-CRAP again. when ever i get around to doing this again i will post a new thread about the O2 problem again. thanks for all the advice.