SlowLS1

I installed the Hot Cam and mac headers with ORP last weekend..... the car has the smell of raw fuel at idle and has heavy black smoke on WOT and decel. and when i say heavy i MEAN heavy! what can cause this condition...is this normal or did i do something wrong? the sad part is that it seems to be getting worse instead of better,like the computer is not able to learn the new mods and is in a closed loop or something.... before the cam and headers the car has run near perfect and has never smoked a bit. Is there any sensors that can cause this and not set a SES light,the only code i get is the p0300 every couple of days,random misfires,which from what i understand is normal. i believe it is so rich that it is washing the cylinder walls, the oil is a week old and has a smell of fuel in it.... my other mods are loudmouth exhaust,tbynes maf ends,160 stat,and a air lid. it is a 98 M6

sorry but i do not know anyone with autotap, i have a MAF translator on order but i'm not so sure that something else isn't wrong! Help i need ideas.

Colonel

Check for header leak. You need to get Autotapped.

Dave Carney

Part of it is moving the oxygen sensor a foot and a half further downstream. Even so i agree with Colonel, there must be outside air getting into your exhaust stream before the O2 sensor to have it that bad.

SlowLS1

ttt

Colonel

You check it yet? That'll definitely do it by giving the ECM a falsely lean reading from the O2 sensor on that bank(s).

SlowLS1

Colonel, I have checked all around the primaries where it is bolted to the head,did not find any leaks, air tubes are blocked off and not leaking. EGR doesn't appear to be leaking either. THe only place i can remotely find a leak is around the 2 bolt collector where the headers mount to the y-pipe. which is below the O2 sensors. I can understand how a exhaust leak can cause richness at idle and part throttle,but i thought that the PCM does not watch the o2's when it is WOT. What variables does it watch at WOT to adjust a/f ratio? Unless my TPS is not showing a WOT condition? THe strange part is it seems to smoke less when it is cold and in closed loop,once the motor warms up,it seems to smoke more. Maybe there is a leak where to primary tubes are welded into the collector? I pulled to 02 sensors out of both sides and they are equally carbon coated. It's as tho it is just dumping as much fuel as it can.

unfortunetly i do not know anyone with Autotap in my area so that is out of the question <img src="gr_sad.gif" border="0">

does anyone havea pinout on the 98 PCM so i can locate the o2 sensors and check the voltage with a multimeter? what should the voltage be at idle,part throttle, and WOT?

Thanks for any suggestions!

Colonel

It's still sounding like it could be an exhaust leak. (Again, Autotap data would really help here.)

Even air entering after the O2s can get to them. The exhaust is not exactly a one way moving flow of gas. Running open headers without extension tubes will cause a TERRIBLE rich condition during part throttle and WOT operation, for example. The outside air gets sucked back up to the O2 sensors giving them a lean reading. I've had first hand experience with that.

"I can understand how a exhaust leak can cause richness at idle and part throttle,but i thought that the PCM does not watch the o2's when it is WOT."

You are correct, the PCM does not watch O2s during WOT but this is one of the most commonly misunderstood things about our fuel systems...

The PCM only learns when it's in closed loop.

WOT (closed loop) fuel is based on what the PCM learned while in closed loop.

This means that if the O2 sensor gets a false lean reading, the PCM will raise the Ltrims to correct what it percieves as being a lean condition. It'll keep adding fuel until it gets the O2s where it wants or until both the Ltrims and Strims max out at %25, whichever comes first.

Remember, the PCM assumes that if it takes X amount of fuel during closed loop, that it will take Y amount at WOT. It assumes that if it needs more fuel during part throttle that it needs more at WOT. Since it doesn't go off of O2 sensors at WOT it will be majorly rich at WOT as well as during closed loop.

[ February 10, 2002: Message edited by: Colonel ]</p>