Mazda stalls intermittently while driving

Maintenance/Repairs
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1

I have a 2000 Mazda 626, V6, 5-speed with 157,000 miles. The car cuts out (as if it’s loosing fuel) and stalls intermittently. This has been happening for 3-4 weeks and neither my regular mechanic nor the Mazda dealer can figure out what’s wrong. Here’s what they’ve tried: new fuel pump (replaced 3 times to make sure parts not faulty), new wires and plugs, new alternator belt, replaced fuel pressure regulator, replaced mass air sensor, cleaned/checked fuel & air filters, replaced coil/distributor (2 times to make sure part not faulty), checked for vacuum leaks, checked ignition/sensors (CAM and others). It has been stalling intermittently for 3-4 weeks, though for a while would not do it when with the mechanic. Also, the check engine light would never come on, so there were no codes to check into. Sometimes after it would stall, it would not start up again until the engine was cold. Recently, it stalled when the mechanic was test driving it. He pulled off the mass air sensor and it started right up. He replaced that part and the car was driving OK for several days. I even took it on a couple 2.5 hour round trips. Today, however, I could not get it started. It would turn over, but not fire and it seems to me that it wasn’t getting enough fuel. Does anyone have an idea about what this could be?

2

@Vagabond
This Must Be Driving You Crazy (And To The Poor-House).

The mechanic should have had opportunity to narrow this down to either a fuel problem or an ignition problem. Is that the case?

I don’t get why the mechanic replaces some parts, even twice, and just checks others, but doesn’t replace them. If the mechanic checked all items then why did he replace them after passing his/her test?

If it’s ignition related and the new coil/distributor didn’t fix anything (twice) then I’d be strongly reconsidering the health of the crankshaft position sensor. They can become intermittent.

What did the mechanic determine… fuel or spark (ignition) problem(s)?

CSA

3

Thanks for the reply. Is there any particular part you think mechanic should have probably replaced but didn’t? Mechanic thinks problem is probably fuel related. Thanks for the tip on the crankshaft position sensor. I’ll have to see where that’s located on this car and, if it’s accessible and easy to replace, I might try doing it myself.