So I was wondering what people have found to replace the tubing that would have been on the air intake duct that comes from the air filter and t's off to the electronic box on the firewall. The plastic parts I have are in good shape but I am having a hard time finding any 3 1/2" ducting to rebuild. I have purchased some 3" plastic tubing pictured and 3d printed a reducer but not really sure how well it will hold up in the long run. My next trip to Home Depot will hopefully yield some kind of ducting but I feel it will be only available in 3" and 4". Any insight would be helpful
Just a follow up to the initial post. Remade the intake hose and hooked up the lean burn tubing on the firewall and the van drives 100% better than previously. Super smooth acceleration with no sputtering at all. Next up is oil change spark plugs then SMOG inspection.
Best of luck with the smog test. Set an appointment, and get the new engine oil good and hot. Lots of smog test centers got rig of their ability to test OBD1 or earlier vehicles. the remaining have raised their prices. Offer to take off the engine covering and have it off to the side, so the tech does not have to do it. They charge extra for vans because of the engine cover potential pain in the ass removal and return time consumption.
Also make sure the battery is totally and completely charged, so it cant accept much amperage from alternator, atwhatever voltage the regulator is commanding, and increase load on engine during the roller/sniffer test.
Running some gumout regane or redline SI-1 through less than 15 gallons before the smog and oil change will likely help it run cleaner.
Would love to see pics if you fabricated new Air hoses. Mine are all beat up, and perhaps restrictive or allowing some warmer underhood air into the tube than there should/could be.