QuestionI recently bought a 1988 chevy nova mfd. by Toyota. It has 173000 miles, manual trans, 2bbl carb. When I went to smog it they said it had 6000 ppm HC at idle. And that this was most likely caused by a massive intake leak they had found. The intake definitely leaks badly. Carb cleaner sprayed at the manifold/head area makes the idle rise. Problem is, it still does this even after I replaced the gasket. I followed the book to the letter when replacing it.
My questions are;
1. Could an intake leak cause excessive HC? (incomplete combustion?)
2. Since the intake manifold is siamesed with the exaust manifold, could they be out of alignment?
3. Can I have the manifolds surfaced together so they mate with the head evenly?
4. The manifold bolts were excessively tight when I removed them, could the flanges be warped?
I know I should rebuild/replace the engine (the whole car!!) but economics won't allow that, so I really need to get this car smogged. Thank you for your time.
Scott
AnswerHigh HC readings are caused primarily by an engine misfire, yes it can also be caused by an intake leak, before doing anything else make sure that the engine does not have a misfire either due to an electrical or mechanical problem(leaking valves, low compression) it may be a good idea to have the engine compression checked.
