Sudden accelaration kick when cold?

[viktor_k]

Busy with questions here... So i recall seeing a thread somewhere about this but didn't pay much attention to it, now can't seem to find it, maybe another forum?

Anyway, when the 5 is cold, and you're accelerating, and once you get passed maybe 2500 rpm, all of a sudden it feels like it just kicked into open loop or something and the car just GOES, i won't let it though, since its still cold. Makes me wonder what's going on there. If the car is cold, isn't it already in open loop? then whats with the extra kick? Is it trying to be in closed loop? would that explain the uneven/hesitating acceleration?

When I say acceleration, I do mean very light throttle, as light as possible...

 

[BRIAN_MP5T]

Electronic throttle body is controlled by the ECU and not your foot.

The kick can simply be something that happens in the code. The ECU may stumble or the throttle could just move quickly when the ECU is in its cold map.

 

[viktor_k]

Yea, i had suspected that electronic throttle could do something like this, but the hesitation at lower rpms made me think that it could be that ecu is switching between closed/open loop. Basically below 3k rpm it seems to be adjusting to the sensors and maybe some sensor is showing improper data so its a little hesitant and then all of a sudden it kicks in and smoothly accelerates.

Do you know if there are scanners out there that can show you more than just AFRs? like if you're in open/closed loop? something that isn't too expensive but can read the sensors?

 

[kw_da]

Ultra Gauge will do it. Shows a lot of stuff - much cheaper than scangauge. It's about $80 with mount. See http://www.ultra-gauge.com/ultragauge/index.htm. I just got one in my 5 - still need to calibrate the fuel.

Do you know if there are scanners out there that can show you more than just AFRs? like if you're in open/closed loop? something that isn't too expensive but can read the sensors?

 

[viktor_k]

Interesting, looks like it outputs raw sensor data, i'm guessing to determine if you're in open or closed loop you'd have to look at some sensor data and interpret it? like oxygen sensor?

 

[kw_da]

For open/closed loop, there is a circle on the default first page. I believe it's a complete circle when closed loop, the circle is open when open loop. I haven't found any definite definition - but it appears to work that way. When I start it in the morning, it's open for a bit. There's ~60 gauges for the Mazda5, I haven't played with it much yet. Just tracking my mpg and eng temp.

Interesting, looks like it outputs raw sensor data, i'm guessing to determine if you're in open or closed loop you'd have to look at some sensor data and interpret it? like oxygen sensor?

 

[00bluees]

Its the vtcs opening. Vtcs is a set of flaps in the intake manifold that stays closed and limits airflow during engine warm up. This helps keep initial exhaust temps higher to get the cats hotter for less cold start emissions among other things. Once the engine reaches a certain temp these flaps stay open, but during warm up they are closed, untill around 3k rpm they open to provide proper air fuel mixture.

So the surge you feel is the engine getting a sudden breath of fresh air whens these flaps open. And the colder it is outside the more noticeable it is. Its perfectly normal.