Check those MAP sensor hoses!

[VetteMed]

At some point, the PO of my car (or a sloppy mechanic) replaced the MAP sensor hose with a section of regular old rubber tubing. I noticed recently, after a backfire which blew the hose off, the hose was oil-softened and had a very loose fit at the MAP sensor nipple.

I ordered a NOS replacement MAP sensor hose from Jerry, and my idle has smoothed somewhat, and fuel mileage appears to be increased by 1-2 mpg so far, which is very significant. I was getting 22 highway/18 overall, previously. Now, I'm getting about 24 highway, 19.5-20 overall. Very significant improvement!

A poor seal at the MAP sensor probably causes all sorts of problems in calibrating proper fuel/air mixture, in addition to being an obvious vacuum leak.

[mike100]

Finding a 10 percent improvement in economy is a big plus with the current price of gas.

I might check mine soon, but I always preferred the old style German fuel and vac hoses that vw used on the air cooled cars with a high underhood heat. Those things are great. they have a cloth weave on the outer layer.

[scottfab]

I used a spring loaded pipe clamp design on the MAP hose in 98 and angled the loose part of the hose upward such that any oil accumulation drains back and out. No problems with it coming off or getting loose ever since.