I thought my car smelled like it was running rich and the plugs looked carbon fouled, so I scanned the pcm using datamaster. At idle I'm seeing blm's of about 155 on the left and 145 to 150 on the right bank. This is in cell 16 at idle in closed loop. Cell 2 at idle in closed loop looks pretty much the same. The mid to high range cells look pretty good, sometimes they get a little high, around 135. I can't figure out what's going on. I'm thinking i have a vacuum leak, but I checked all the vacuum lines, put on new header gaskets (earls performance gaskets) and tightened all the header bolts well, I even replaced the intake manifold gaskets. The car runs great, the idle is slightly rough but I'm not sure how much this has to do with the cam. I have only had the car about 4 months and I have been trying to get it all straightened out. I'm thinking maybe the pcm tune is crappy? The previous owner said it has a hypertech power programmer tune. I think he said he used the heads/cam/supercharger tune. This car doesnt even have a supercharger so I'm thinking maybe it is programmed to run too rich for the mods? I'm just concerned about the oil getting thinned out from all the extra fuel being dumped into the cylinders. The previous owner also said he decreased the fuel pressure slightly, the car has an adjustable fpr but i havent tested the pressure yet. Would this change the blm's to read high? Also, the car has a Holley 52mm tb. I read a post that said the IAC counts should be around 20 - 40 at idle. A datamaster scan before I did the intake leak fix showed IAC counts of about 25 while idling. My last scan showed the IAC count at 15 while idling. After taking the car out for a drive, the IAC counts are reading 11 at idle now. The TPS voltage is 0.35 at idle. I'm really not sure if the IAC and TPS voltage settings have anything to do w/ this rich running condition but i thought i would throw them out there. Any advice anyone could give me would be greatly appreciated.

Thanks,
Mark

 

Decreasing the fuel pressure will lean the engine out , but the pcm will compensate in closed loop. The BLMs being in the 150 range is a direct result of the pcm correcting for the lower fuel pressure IMO. You need to get a fuel gauge on there and set the pressure close to stock(41-44psi) and the BLMs should drop.

Now when you first start the car and your in open loop you most likely are lean. High NOx will burn the heck out of your eyes and youll think its raw fuel but it smells alittle different .

 

pretty sure you have a vacuum leak somewhere. this will cause BLMs to increase b/c unmetered air is entering your motor which is sensed by your O2 sensors telling the PCM to add fuel. the other indication is the fact your IAC counts are so low. the expected value should be in the 30 range so your 15 is telling me the car is getting air from elsewhere(vacuum leak) so the IAC doesnt need to open as much to keep a constant idle.