Destructimus

Ok, this is a mess of info so be patient with this and thanks in advance. This could even be entertaining to some. Skip to the last paragraph for just the questions I have, aka the short version.

My car has been occasionally getting a code 13 for the O2 sensor circuit, and for a while now has been backfiring when I let my foot of the gas at driving speed and hunting in idle once it gets warmed up, but on the throttle it's fine.

I since replaced the O2 sensor, have checked the voltage on the tps (my haynes manual mentions a sticking tps is a possible reason for a 13), and even driven with both disconnected to allow it to run in open loop and with the watered down auxiliary tps settings when it's disconnected. (gives a code 22 i think) Except for the tps delete, I still am getting a 13 no matter what, hooked up or unhooked.

Now here is the fubar part: I think the previous owners (half a$$ed) rewired the car, because the wire coming from the 02 sensor is green and the wire right next to it, for the knock sensor, is red. My haynes manual says the o2 wire should be purple, and the knock sensor wire dark blue. Now, then we have the green wire being cut and joined into the red wire to go back to the ecm and the knock sensor wire being hooked to the green,(they swapped) but the wire initially coming from the snap connector of the o2 has silver stranded wire, but the one heading back to the ecm has copper wire (the green ones), so I'm not sure if this guy was colorblind and got his reds and greens messed up, or if he hooked up the wire to the wrong slot on the ecm and realized he messed up and tried to change at the engine rather than the ecm. Running new wire to the ecm itself could be tricky because I wouldn't know what to hook it to once I got there because of this and the colors are changed but I'm not sure if they are cut somewhere buried in the harness.

When I tested it with the wires hooked up to their own colors, I got a code 44 for lean exhaust. Now, this doesn't make sense either because I have a 255 lph pump, 30# injectors (modified pulse width though) and I cranked the fuel pressure up almost as far as it would go on my afpr so if this was the correct wiring I don't think I'd still be running lean at idle, and a knock sensor is supposed to put out 8 to 10 volts versus the .1 to .9 an o2 sensor puts out, and I would get a code 45 because my voltage would be too high and my mixture would be too rich. Not to mention my car runs like crap until I get the code and my ecm puts it back in open loop. Another point of interes is that I didn't consistently get a code 13 until I tried and failed to replace the 02 sensor, and then kept getting one after I succeeded three days later. (maybe I knocked something loose?)

My car is done f'ed up. So uh, can anyone actually verify from experience that the o2 wire is supposed to be purple? At the ecm the only one I see is for the vss. Anybody have any ideas wtf is going on aside from maybe a messed up ecm? Anybody know what plug socket number on the ecm I should look for an 02 sensor wire? Thanks.

Destructimus

Anybody? I slept on it and the only theory that makes sense still is a bad connection at the 02 sensor. I just need someone to verify the color of that wire so I can try running a different one to the ecm.

Toehead

On my car, it is purple.

Destructimus

Thank you sir... Well damn. Could anyone with an 89 or later ecm look to see what pinhole that wire goes into? If you look closely, they're numbered on the plugs where they hook up to the ecm.

kooga

From my 89 service manual....
Ppl wire , o2 sensor signal D7 .
Tan wire , o2 sensor ground D6

Destructimus

Cool. Thanks, I'll let you know what I discover later today.

Destructimus

Hmmm... my haynes manual says the ecm is different for 90-92 than 89. There are two d6s and two d7s on mine too, neither have any color wire I should be looking for. My closest hits in regards to the colors I need are a tan one and ugly pink one that I guess could be purple or maybe the same if the one under the engine faded enough. They are at C14 and C15 I think. Could someone verify this for me on a 1990-1992 tpi 350?

kooga

Maybe some info in this webpage...
http://chevythunder.com

Destructimus

Didn't look at that page kooga, but I did find what I needed here:
http://www.eecis.udel.edu/~davis/z28...730v8tpi-1.jpg

I went out and tested the wires while the car was running and I am getting voltage through my 02 sensor circuit, and the voltage through my tps was consistent. I didn't test drive it and I didn't get the engine light while this was happening, but it did behave strangely while I had my vom hooked up to the 02 sensor and tps wires. I don't know if that is normal though. When it was acting funny, the voltage did jump around a bit, especially on the tps. Think I should just say to hell with it and replace it (the tps)? I'm stumped.

kooga

Found this information at chevythunder...
Code 13- This code is set by a O2 sensor problem. It is normally set when there is a open circuit or the O2 sensor is coated with soot from a over rich mixture.
The only difference between open and closed loop, is that during close loop the ecm is monitoring the O2 sensor, to trim the air-fuel ratio to 14:7.
The throttle position sensor (TPS) is a variable resistor that changes resistance as the throttle angle is changes, this sends a voltage signal back to the ecm, along with the other sensors to calculate fuel injector on time. Normal voltage at idle is around .55V, while at WOT it is closer to 4.5V.
0,45v is the average voltage from the o2 sensor , and an open sensor circuit or cold sensor causes "open loop" operation.
Maybe just try drawing a new wire from the o2 sensor and see if it fixes the problem? Perhaps when you installed the o2 sensor something was messed up?Also check that the wire from the o2 sensor isn´t close to the ignition system especially the spark wires. Another thing that could f*** up the o2 sensor is silicone .

Destructimus

So tonight, after going to Woodward Ave. to race, I popped my hood in the dark and looked closely to see my spark plug wires arcing pretty crazy. With a 6al and blaster coil, I guess that qualifies as a ground issue lol. It makes sense now, because it seemed like this all started around the time I put a blaster coil in it, which would only increase the problem. I'll replace those and post results. For a car with a bunch of bolt ons, I think I did pretty good taking down a charger R/S... beat him by a nose at 115mph woo!

Destructimus

Okay, put the new wires on today. A new set of the same- MSD 8.5mm superconductors. All cracked and stuff. They DO go bad like any other wire. Anyway, seemed like the car ran better expecially at first. On the first two drives with it, both about a half hour, I got no trouble codes. On the third, I got one. Got home and checked it, but it wasn't for a code 13, it was a 22 - Throttle position sensor. That was kind of what I thought most likely all along, so I'm going to be replacing that and I will post my update as soon as I do. Thanks to all who've looked so far.

Destructimus

So I cleared my computer and last night I got another error code- a 32 for the egr. It is possible that I just miscounted. I might have been drunk or something. It happens. In fact, it's happening right now. Anyway, I remember when I would push up on the valve when I had the plenum taken off this winter, there seemed to be some resistance. Not like there was a bunch of carbon build up, but more like just some vacuum pressure. Is the EGR supposed to move almost entirely free? I was going to go to autozone or murrays today to have them pull one out so I could see for myself, but let me know what you think. The EGR does make perfect sense in regards to my problem though. Was second on my suspect list behind the tps.

kooga

Code 32 means that the egr diagnostic switch was closed during startup or that the switch wasnt closed under the following conditions , coolant temp above 176f , egr duty cycle commanded by the ecm is greater then 48% , tps less then wot but not at idle , codes 21-22-33-34 not present , all conditions must be met for about 4 minutes....

Destructimus

So what you are saying is that the egr valve could be stuck open at times, misinforming the solenoid so it has a duty cycle of above 48% or that my solenoid could be malfunctioning, once again messing with the duty cycle? Either way, I'm going to start by inspecting the EGR valve by simply working the mechanism by hand and testing the solenoid by running a current through it to see if it clicks. I will try to do this tomorrow.

kooga

The switch attached to the body of the egr is what causes the code 32 , but , as I have learned its not that simple just pointing to what the service manuel says....It can be as simple as -the switch is malfunctioning but your other codes points towards some fault that causes several other codes , like the tps...Sometimes its a guessing game to figure out what is wrong! Do you have an ability to maybe scan the car with datamaster or an equal program?

Destructimus

Went out to check the old EGR and my large mutant hands could only get one finger on it, even with the throttle bracket removed. I could barely move the valve and it sounded crusty when I did. Hoping to get one and install it this week to see what happens.