My question is how far back from the collector flange should the O2 sensors be when running open headers. I normally run through the exhaust with dual cutouts. I pulled the y-pipe and took it to the track and it was VERY RICH ..black smoke and fuel would burn your eyes at idle. It eventually got so bad that it has developed a miss and will not even clean up. Hopefully it's just a fouled spark plug. The 02 sensors are about 3" from the opening with the y-pipe off. With the y-pipe on, they are about 10" from the cutout opening. Evidently 3" is too close......I'll be putting the y-pipe back on for sure. Would the 02 sensors being that close to the opening cause the rich running situation? It has never done this before..... Hopefully I don't have another problem somewhere....

 

Yes it would. I would say at least 12" from the opening. Another option would be to unplug them so that the PCM uses tables. Also at WOT it shouldn't hurt you any since it uses tables anyway.

 

Well....I pulled the plugs and they were coated with wet black gunk. I swapped them with fresh plugs and put the y-pipe back on. When I crank it, it still seems to be running rich....strong fuel smell coming from exhaust... Could the excessively rich condition that fouled the plugs have harmed the 02 sensors?

 

I pulled a few of the new plugs out tonight and they are black also. There is black smoke and raw fuel blowing out the exhaust. It does this immediately when I crank it....on a cold engine........ What do I look for now??? Does the computer read the O2 sensors immediately after cranking? If so, the O2's may be bad??? If it doen't start reading the O2's immediately, what else could it be???? Fuel pressure regulator problem??? I haven't driven the car at all because it will surely foul the new plugs quick....any ideas suggestions.......

 

Do you have anything to monitor the PCM with? What kind of tuning do you have? If you want to check your fuel pressure, you will need a test gauge.

 

I don't have anything to monitor the PCM.... The car has OBD1 conversion with a custom program from LT1 Motorsports..... I have a Snap On Fuel Pressure Guage, but somehow I misplaced the GM rail adaptor.... I will see if the Snap On man has one tomorrow so I can check the pressure. I also will get a Snap On scan tool from a friend tomorrow..... If the fuel pressure is ok.... What should I look for on the Scan Tool? Or better yet, will the scan tool even show me anything worthwhile?

 

the very MIN is 8"
i seen that in a diffrent post a while ago.

 

I've been taught as close to the header flange as possible but no more than 8 inches just like OpCode said.

 

I will be scanning the car tomorrow.....what parameters should I be looking at? I checked the fuel pressure with the car running and vacuum line off it has 47lbs......but, when I rev it to about 5k, the fuel pressure drops to around 30lbs....... At idle, the car is VERY rich and will blow black smoke....... I drove it down the road last night..... In park, you can rev it up and it will rev fine(of course it still smokes) but when I got on the road, every time I hit the accelerator hard, the car would completely stumble and nearly die. When I got back home, I put it in park and it revved up to 5500???? What should I be looking for tomorrow when I get the scanner hooked up?

 

One thing to try would be to unhook your battery for 15 min or whatever it is to clear your ECM. Your computer probably learned a new AFR while you were driving before and that condition is still being felt. Reset your computer so it won't have any of the learned values and the problem might go away. Just an idea.

 

Sorry I didn't mention i've tried that......

 

I couldn't see anything that looked out of wack while scanning except 02 numbers dropping into 150 range when revving over 3800 rpm....Fuel pressure was also dropping about 20lbs at the same general rpm range........ Problem Found!!! NOS Inline Fuel Pump was the problem!!! Removed it completely and fuel pressure is remaining constant througout rpm range and car is running great..........