Blowin Smoke, Rebuild & Emissions

Brad Bartilson

New Member
Feb 2, 2002
I Failed the IM240 test again (here in CO, high altitude)-High CO (9.0 vs. 3.0 limit) and HC (47 vs 20 limit) indicating too rich.
So far I've:

-installed a new GM 02 sensor (much more active than the Bosch)
-tried higher and lower fuel pressure (I have 009 injectors)
-installed a new 70mm throttle body (no leaks)
-tried everything to get leaner, to no avail (LS1Maf/translator plus on leanest position). Don't see any difference on EGT's.

I had the engine rebuilt a year ago, have 5K miles on it. I still blow smoke at 20psi. At 2.5K miles on the rebuild, I installed high flow heads, still saw the honing marks in some areas on the cylinder (Hastings moly rings). My compression checks are good. A leakdown check showed 12%. The leakdown check shows only "fair-poor" sealing past the valve seals. I use a quart every 1k miles.

Question: Could my oil consumption be the reason my EGTs are low and the high emissions. If it is going by the valve seals, would venting it to atmosphere get me by emissions (right now I have the passenger side vented into the intake)? If it is going by the rings, would this also help? Would plugging the EGR reduce the emissions by increasing my EGTs?

all help appreciated.

Brad 87TR
Where are the BLMs at idle and cruise? Who's chip are you running? Those numbers look really rich. I suspect that if you cure the rich problem, then the emissions will fall into place. The valve seals may not be an issue just yet. I just had a problem with my EGR valve. It appears that it was hanging open slightly and I could not control BLMs. I installed a EGR block off plate (before heading to GM to buy a new EGR valve) and all of a sudden, the IACs dropped to zero and as I adjusted FP, the BLMs would increase (with the lower FP). So when i returned home, I installed the new EGR valve and the IACs were still at zero, until I adjusted the minumum idle screw. On I/M240, I would not suggest removing the EGR valve. When you finally get fuel control, the NOx will rise slightly and without an EGR, you may have problems passing NOx during the acceleration from zero to 58mph.

I have two chips, both Street and 93 octane. One came with the 009s (used, unknown origin) the other I had Joe Lubrant cut, leaner for my high altitude problems. The BLMs from chip that came with the injectors were consistently low (at idle and steady cruise) . This is the chip I did the emissions test with. The Lubrant chip was much steadier around 128. So you may have something there. My attention was largely on EGTs to analyze for rich/lean, and didn't see much difference between the chips.

I'm going to do some testing by blocking the vacuum to the EGR as well. [By the way I've done extensive leak checking with an air compressor, and noted that the EGR is difficult to get sealed well, even with a new gasket].