TunerLexx

Recently, I failed emissions because of high nox ppm. I first thought O2 sensors--didn't do anything, then I figured cats since it's the only thing specifically controlling that. When I went to bolt up the new cats (supposedly for 91-99 sc400) I noticed they were half the size of my originals--I have a 93 1UZ. They were also about a centimeter shorter lengthwise than the originals. I tried to put em in anyway--they bolted to the exhaust pipes fine but when it came time to tighten the nuts on the threaded studs for the exhaust manifold to cat setup they didn't tighten all the way flush( btw I had to slide the cats in to the exhaust manifold and tighten them on first--I only noticed the flushness was a problem when I saw how well the pipe went to the cats after the exhaust manifold was tightened to the cats).

My question is whether or not the fact that the cats aren't completely flush with the exhaust manifold give me an exhaust leak since I can't exactly fit my hand in between the engine and the upper part of the cat to check.

Also, would that exhaust leak jack my gas mileage? And does anyone think that since the exhaust manifold wouldnt bolt all the way up to the cats that maybe the studs are stripped--and if so would I need new exhaust manifolds if the studs 'are' stripped? I already had to grind down the nuts on the cat heat shield since the threads were lookin' like a pillsbury biscuit and they were welded on >_<

Thanks so much to whoever wants to try to answer all my crazy questions

TunerLexx

Small detail--when I slid the cats onto the studs on either exhaust manifold they both had about the same gap that I couldn't seem to lose (the cats slid on fine) the 'only' reason I brushed it off was because I have those aluminum gaskets--the cats didn't have gasket grooves on the cat to exhaust manifold side--I assumed the gap was from the gaskets even though they flatten as you tighten down on them.

Subjug4tor

iTrader: (1)

High NOx is rarely ever caused by a bad cat... it is a sign of high engine temp, or a lean mixture. The EGR not working correctly is a common culprit, run the tests on those parts as per the service manual.