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Vapor lock in the 2002 Miata

My Miata stalls out on the highway but not on residential streets. If I open the gas tank ,it starts up again. This has happened with a full tank, 1/2 tank and 1/4 tank. How can I fix this?

What year model? Apparently the vent is plugged.

How many miles on your 2002 Miata?

It’s not vapor lock. Vapor lock only happens with carbureted vehicles. Fuel injected vehicles do not vapor lock.

I’m surprised the CEL hasn’t come on.

I would have the fuel pressure checked, and also the evaporative emissions control system.

Has the fuel filter ever been replaced?

I have 71,000 miles on the Miata and the CEL light has come on and off for two years. I have it regularly maintained. The 1st time it happened on the Blue Ridge Parkway.The second time in the mtns. again, so we thought it was an altitude thing, but it happened on the highway at home (in low elevation) the 3rd. time. I only drive a short distance (10 mins.)to work on residential roads under 45mph. It doesn’t seem to happen when I 'm not on the highway.

So, when the CEL comes on and off, what codes are stored in the car’s computer?

The CEL is an early warning system. It alerts you to developing problems before they become very expensive problems.

When you say the CEL has been coming on for two years it makes me think you’ve ignored the warning, and done nothing.

Is that the case?

No I haven’t ignored it. My mechanic can’t seem to find the source that sets it off. We have changed the filter, oil and do regular maint. He thought it might be a faulty sensor and he eventually replaced that. Maybe I need to switch mechanics, but I trust this guy.

If you had a light, then there should have been a code, or at least a stored code. Have you tried having the computer “read” at a dealership?

P.S. the CEL doesn’t stay on and I don’t know what codes come up on the computer. We have been attending to this CEL problem for two years and have gotten nowhere. That’s the problem. I get it in the shop and although my car always seems to be fixed in the short term, the light comes back on. Do you know why opening the gas tank fixes this last issue? Or is it possible that just turning off the car and restarting it helped? Urgh! I promise that I haven’t ignored my cars cry for help. I love my Miata and want to keep it till I can’t physically drive it anymore.

Sounds like you might need to try a different mechanic. The gas tank issue points to the evaporative control system or the fuel pump, both of which can be checked out. Also, any time the CEL light comes on a code will be stored, and your mechanic should be able to read the code. A car parts store can do it. Find out what they are and post them back here.

What year is it?

When you remove the gas cap, is there an inrush of air? Usually there is a vacuum relief valve in the gas cap. I have seen some used caps that do not relieve the vacuum well.

If you have not done it yet, try a new gas cap.