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1998 Mazda Protege Won't Start Cold

I have a 1998 Mazda Protege LX 1.5 L 4 Cylinder and i have been having some starting issues, and stalling at stop lights.

To be clear i have replaced/cleaned, Injectors, Spark Plugs, Spark Plug Wires, Distributor Cap, Distributor Coil, Air Filter, Cleaned MAF, Cleaned the EGR Valve,

My car won’t start in the morning, just gives cranks but if I press gas pedal it starts and have to keep it until engine gets hot enough. then it works till the car cools down again, and repeat the problem in the morning when I have to go to work.
When the car is warm it starts fine but has idle issues regardless of temperature.
As usual when the engine is cold or cool, it won’t start. Visited 2 different mechanic shops and the problem still exist, I don’t know how and what they did it, it only worked for couple of months and the engine noise was bit high, I believe he just increased the idle, When i am at stop lights it has a rough idle and tries to die, When it idles it idles rough, Every once in a while i get a CEL Cylinder Misfire on cylinder 4. I’m confused on want to do , Don’t know what else to do and its getting tiring, The car also feels like a lack of power. Gonna Change the fuel filter today, and see how it goes, If anyone has any suggestions please let me know.

My wild guess would be that the temp sensor is bad and the ECU has no way of knowing the engine isn’t at full operating temperature. When the engine is cold, the ECU bypasses the upstream oxygen sensor and runs the engine rich based on a predetermined algorithm. If the ECU doesn’t know the engine is cold, it’ll run it too lean based on the O2 sensor input. It also won’t elevate the idle, also necessary on a cold engine. Since the ECU has nothing to compare it to, a bad temp sensor also won’t trip a fault code, so you probably don’t have a CEL illuminated.

However, this is just an educated (?:stuck_out_tongue_winking_eye:) guess. The output from the temp sensor should be checked, although a new sensor might be cheaper.

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Will look into this, Thank you!

I agree with mountainbike, but you should not guess if the temp sensor is bad. See if you can buy/borrow a scan tool to read the sensor information from the engine computer. You can start the car and see the temperature reading increase as the engine warms up. If it doesn’t look right, you know to fix the sensor.

The problem might be with a dirty/defective Idle Air Control valve.

The IAC valve controls the engines idle speed under all conditions.

Some of the symptoms of a dirty/defective IAC valve is, the engine won’t start unless the gas pedal is depressed, the engine idles rough, and the accelerator must be depressed to prevent the engine from stalling.

Sometimes the IAC valve can be removed and cleaned to fix this problem, and other times the IAC valve needs to be replaced.


In addition to the other good suggestions already given . . .

Check compression

On this engine, the valve lash tends to get tight over time, which leads to lowered compression, which leads to hard starting cold

Okay thanks everyone!

All good ideas. I’d guess it is the idle air control gadget. A car of this vintage, if it were mine I’d remove it and do a bench inspection and cleaning of the idle air control contgraption and probably remove and clean the whole throttle body unit while I was at it. Depends on how the engine is configured tho, on some engines this would be too much work. On my Corolla its a pretty simple job. And I had to do that due to a similar problem.

Other ideas

  • EGR problems can cause this, if you have an EGR.

  • Vacuum leaks can cause it too. A shop can check all the vacuum hoses and vacuum operated gadgets to make sure they are holding vacuum properly.

I agree and would be looking at either the IAC or the temperature sensor. That would be the engine temperature sensor. Sometimes there are two. One for the engine management system and one for the instrument cluster.

Okay Thank you! I haven’t had time to clean the IAC yet, I’m gonna look at it, But i’m hopeful that its just that.