My 93 prelude (h23a 131K 5sp) smokes at idle sometimes, usually with slight uphill slope conditions. No smoke at speed or under acceleration. Several mechanics suggest its the valve stem seals are too old. The compression is good 178 -185 psi per cylinder, the plugs look good, the pvc valve checks out. No coolant loss or significant oil loss. We changed from 5W-30 to 10W-30 and the smoking seems to be significantly reduced. However the problem is intermediant. Could it be something simple?

Any other suggestions? If its the valve stem seals can they be replaced on the car, or should i pull the head and get it reworked?

 

Is it truly smoking under acceleration? Or is it doing it in between shifts or on decel. If it's doing it at idle while uphill, the valve seals are a definite possibility. Bad valve seals will usually be the culprit for little smoke puffs in between shifts and under deceleration.

 

i have a 2000 prelude 5spd and it smokes when i have a hard take off or rev da hell out of it. i went from 5w-30 to 10w-30 and it did stop smokin for a while. but then my check engine light came on n then i had 2 get a new o2 sensor n now it smokes sometimes like when itz really hot outside. also da honda dealership said it smokes cuz itz not lev or ulev rated(or sum bullshit like that) so dont worry about it, itz stilll a lude.

 

You described it well, there are "puffs" of smoke while shifting after idling a long while. If the car isn't idled for 4 or 5 minutes no smoke at all. Certainly nothing to remind you of bad rings. I thought valve stem seals would produce smoke at start up, and this one doesn't do that. Only smokes after extended idle. No smoke during hard acceleration only while shifting.

 

It's your valve seals. No doubt. My 93 Vtec does it, too. I got 138,000 miles on it. Nothing to start flipping out over, but definitely something that'll gradually get worse with time. You can buy seals, but replacing them is a PITA.