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Ask sprinkles08 Your Own Question
sprinkles08, ASE Certified Technician
Category: Mazda
Satisfied Customers: 22993
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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1993 protege runs fine when cold then starts to stumble.

Customer Question

1993 protege runs fine when cold then starts to stumble. Hard to start when warm.
JA: Will the headlights turn on? Is the battery fully charged?
Customer: Yes
JA: Are you fixing your Protege yourself? What have you tried so far?
Customer: Local shop replaced,plugs, ign wires, cap, air filter, fuel filter a $500 tune up still same problem.
JA: Anything else you want the mechanic to know before I connect you?
Customer: No
Submitted: 10 months ago.
Category: Mazda
Expert:  sprinkles08 replied 10 months ago.

Hello and welcome to JustAnswer!

There are quite a few things that could cause the engine to run poorly and it will take some testing to determine what is going on. If it runs fine initially when cold then one of the first things that comes to mind is an inaccurate upstream oxygen sensor, it's signal is ignored when the engine is cold.

Have you checked for fault codes?