Bought a brand new 350 from the local dealer for only $1744 for my 220K miles '94 Suburban. The old one had barely flunked the ASTM 5015 elevated rpm "roller" test for CO (10% high) and HC (5% high). It was "using" oil; I never found a leak but had to add 2-3 quarts every 7500 miles, and the plugs never looked bad. Leaking antifreeze from freeze plugs. Plus I plan on keeping the truck for a long time, with the price of new Suburbans being what it is. The new motor shows borderline CO, NOx, and 50% high (first test) to almost 100% high (second try) HC. I've got almost 1000 miles on the motor. I'd have expected the rings to be seated by now, no?
Tomorrow I'm going in to try to get an emissions waiver, but the car still has to pass an idle test for HC and CO. My elevated rpm (roller test) HC reading this last time was 217 ppm (versus a limit of 118), and the idle limit for HC is 220. I don't think it's gonna make HC, since all of the postings I've looked at show higher emissions at idle than elevated rpm.
The plugs are new, the plug wires have 18K miles on them, catalytic converter has 100K, the O2 sensor has 20K. If not the rings, I'm thinking it's the cat. Check engine light is not on and no trouble codes (except system OK) are flashed when the appropriate wires are jumpered.
I plan to change the oil to 10W40 (from 5W30) and check the plugs tonight.
Any way to diagnose the catalytic converter without just buying a new one and trying it? Other comments?