Hi all,

Bought a 2010 Mazda 3 with the 2.5L and 6 speed back in March 2025. It had 230xxx km and in great condition and drives well. Initially at purchase it was indicating 9.4L/100km average at most times.

I stupidly attempted the throttle body grounding wire trick whereby you connect a grounding wire between one of the throttle body bolts an the neg terminal of the battery and it has been said to improve throttle response. At that point my fuel economy jumped to roughly 13l/100km but that initially was not a concern as the ECU was recalibrating following a disconnect.

I removed the grounding wire after a week and unfortunately my fuel consumption has remained high. in the 10-15l/100km range.

It has an aftermarket Corksport cold air intake which I bought a new cone filter for. I also bought a new MAF sensor and installed. Am planning on re-installing the stock air box because the faux cold air intakes are annoying.

Did I cook my ECU, injectors, or throttlebody with the grounding stunt? Cracked throttle body or intake leak/vacuum? Could a non Corksport air filter be acting as a choke on the intake, would a choke effect pull more fuel like in a carbureted engine, no right?
Anyone know a good ECU reset or tests I could run, no codes showing.

Thx Zoom Zoomers

 

Welcome to the forum

 

At that miles you may want to do a basic health testing of the engine first?
Compression test possibly both dry and wet depending on the results and if you do the test properly
Followed up depending on the compression test a Leak down test

No, you did not harm anything, nor did you harm the ECU by the install of the ground or disconnecting the battery. If it started and no check engine light = "don't worry about it"
Yes that BS about grounding the TB is a MYTH due to some that really only needed to clean a few things neglected and did a bailing wire and duct tape approach to resolving things. LOL

Your MPG is not really an example of good or bad. You need to do at least 100miles (160klm) and establish an average MPG? You cannot compare or use past vehicles or what other post without at least that established average first.

No you cant "re-set" the ECU as that requires socialized equipment but nothing you posted suggest that service needed?

When you say no codes did you scan all the minimum 3 area's of the ECU? And used a direct connected ECU scanner to the OBDII diagnostic connector in other words NOT a blue tooth scanning device/program? My guess is no! But here again nothing you posted suggest you have any issue?

 

** https://www.mazdaforum.com/forum/maz...tle-body-3069/


I saw you taking interest in this thread so posted a couple pictures for you .

** UPDATE : the picture I posted did not show.??

 

I installed a wire 3 years ago to proves that it is a MYTH about grounding the throttle body. If there is a problem, it is due to a connection issue at the connector or the connector mate on the throttle body itself. Attaching a ground lead is like placing a Band-Aid on a cut that needs stitches.


UPDATE: I am not sure what happened to the pictures I was on my ipad last night and that happens I will repost the pictures later.