2003 Mazda B3000 5spd Manual Problems

[Coltonk]

I have a 2003 Mazda. When the engine isn’t up to temp it runs fine but once it’s warmed up the problems start. Around 3k-3500 the truck falls on its face like the flip of a switch. And will randomly put power back in. This continues back and forth until you reach the rev limiter. I just can’t figure out what would make it jerk back and forth like that but only when warm. Thanks in advance.

 

[Dirtman]

I'd be inclined to check the ECT sensor first.

 

[Coltonk]

Would that cause the jerking when only reaching that rpm?

 

[Coltonk]

Replaced ect no change

 

[gw204]

Check engine light on and flashing? Any codes?

 

[Coltonk]

Yes on and flashing the only code is for evap system. And fuel cap light is on as well

 

[Coltonk]

Just started flashing today when I changed the ect sensor

 

[gw204]

Had a very similar problem in an '03 Suburban due to a bad O2 sensor. When cold and in open loop, it ran fine. As soon as it warmed up a bit, entered closed loop and began reading the O2s, it would start stumbling, pump black soot from the exhaust and the cel started flashing. I don't remember if it actually threw a code or not. That might have been before I had the bluetooth code reader.

 

[Coltonk]

How would I know if it’s a bad o2 sensor? Is there a way to test them or do you just replace and how it’s fixed?

 

[Dirtman]

Flashing check engine light means there is more codes than the evap system. The check engine light only flashes when there is a misfire condition so you must have a p030× code. You need accurate data for us to help. And saying "there is a code for the evap system" is not useful information. We need the actual code. There are about 30 codes for the evap system, some of which can cause engine running issues.

 

[gw204]

Get yourself an inexpensive bluetooth code reader. I have this one to work with a cheap Android tablet I got...

https://www.amazon.com/gp/product/B005NLQAHS/?tag=959media-20

Then download the free Torque app...or pay the $5 for Torque Pro. The combination of those will give you the ability to retrieve codes and look at live data (you'll have to google for the specific test to do). Don't just fire the parts cannon.