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Hi guys, i´m new to this forum but been watching eric the car guy on youtube since long time ago!
I´m a fairly rookie technician and i have a small shop in my house, i mostly deal with domestic brands (Ford, chevy, dodge, mercury, cadillac, lincoln, etc)
I almost never have this kind of hair pulling problems and most of the time, diagnostics are pretty much straight forward.
Recently a customer brought a 2002 Mazda Tribute DX 4cyl 2.0 5speed, he complaints about hard starts on cold engine, missfiring and low power.
Long story short, the missfiring and low power were due to a bad spark plug wire making cyl 1 miss, i replaced spark plug wires and that worked like a charm even for the cold start issue.
I performed basic maintenance as per customer request and tested the vehicle multiple times, in multiple situations (specially cold start) and the SUV never failed again.
Customer was happy with the result but a couple of days later the cold start issue was back, i now have the SUV in my shop again…
And indeed the cold start issue persists, the engine acts like it´s flooded and will only start if you press the gas pedal all the way down while cranking, it starts but backfires through the intake, and slowly catches up. the rest of the day you can start it as many times as you want and it will work like a champ.
I already checked fuel pressure, spark plugs, spark, fuel pressure regulator, ckp signal, cmp signal, battery….
The problem persists and it always act like it´s flooded, but only on first morning start…
I´m at a loss here…
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4 things come to mind,.. #1 check the PCV vacuum supply hose the rubber elbow to the PCV. (don’t just look at it, run your finger on the back side and see if it’s deformed) #2 I can’t emember without lookingit up.. but possible timing belt issue . #3 Wrong oil. causeing the VVT to go nuts. and #4 check out coolant level and your ECT for proper signal when COLD. And least likely a MAF signal… or even just try to clean it.
Thanks for your response Woody
1st. PCV hose is in ok condition, no cracks or any kind of damage to it.
2nd I tought about that too, but the car works just fine the rest of the time, it has power, idles fine, starts fine (when hot)
3rd Does this engine has VVT? i don´t recall the zetec engine having VVT
4th Coolant level is ok and ect signal on cold starts is ok tooMAF? I really don´t think that has to do with the cold start issue, because the pcm will disregard MAF and O2 sensors when the engine is cold, because it has a fixed fuel injection table for cold starts until the engine warms up. Correct me if i´m wrong here.
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