Mazda MX-6 Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
Hello I am new here I have a 1997 MX6 2.5 V6 I recently installed a timing belt the engine runs smooth but very predictably when the engine is at full heat it will buck very hard approximately 3200 rpm every time. The car does not want to surpass those rpm. But when the engine is cold it can rev too close to 6000 smoothly. This makes acceleration almost dangerous as the engine almost stalls until i back off the gas and drop below 3200 -3500. I thought maybe injector fuel pressure regulator. Any advice?
 

·
Registered
Joined
·
2,376 Posts
Hello I am new here I have a 1997 MX6 2.5 V6 I recently installed a timing belt the engine runs smooth but very predictably when the engine is at full heat it will buck very hard approximately 3200 rpm every time. The car does not want to surpass those rpm. But when the engine is cold it can rev too close to 6000 smoothly. This makes acceleration almost dangerous as the engine almost stalls until i back off the gas and drop below 3200 -3500. I thought maybe injector fuel pressure regulator. Any advice?
Check your engine ground connections including battery - connection, If a ground wire connection to the engine was missed or is loose than the load on the other ground wires is increased, If the load on the remaining ground wires is greater than their capabilities they will get hot. The hotter the wires get the less current they can flow. Current (flow/amperage/volts...) demands increase as rpm's increase.

Why are engine grounds needed and what positive voltage do they have to match in current flow you might ask. The alternator, the starter but most importantly The spark plugs, they get a high voltage positive current from the coil, this high voltage + current is delivered through the center electrode, when the plug fires this High voltage + breaches to the ground electrode that is part of the plugs threaded body that screws into the head and grounds the spark plug to the head/engine. As rpm's increase so does the voltage discharged by the coil and the ground requirement to complete the flow of electricity are increased. Also working against the situation is the alternator, the higher the rpm's get the higher it's amperage output gets under electrical demand fighting for more of the ground path to the frame and battery.


The symptoms of insufficient engine grounds on the ignition system (spark) would be:
Start the car and drive without issue. Floor the car and at a certain rpm (no matter what gear) engine spark will break up and the car will stop accelerating.
Depending on the size and number of engine grounds when an insufficient ground path is connected to the engine, the engine may accelerate to higher rpm at first but the insufficient ground acts as a resistor and the energy (voltage) it can't pass through it gets converted to heat, as the wire temperature increases the current it can carry decreases and engine spark will break up at lower and lower rpm (coil voltage).

If your problem is insufficient grounds to the engine than the ground wires are at their flow limit way before 3200rpm and building heat between that point and 3200 rpm, so even if you don't rev to 3000rpm or higher or cause the car to buck the wires are getting hot.
Insufficient, corroded, broken ground wires can get hot enough to seriously burn you and because the wires are shielded (plastic coating) heat will dissipate through the path of least resistance and the wires will be hottest at the exposed metal connection points at the ends, this heat can travel all the way back to the grounding terminal on battery, I bet there are thousands of people out there who had engine issues or never noticed any issues but had engine ground issues walking around with - battery terminal burns on the palm of there hand.

So check grounds when the car hasn't been driven for hours or check them for heat before touching them.

If you want to test this ground theory without testing and checking grounds go to canadian tire or your closest affordable auto parts store and buy one of these:
https://www.canadiantire.ca/en/pdp/motomaster-braided-ground-0112000p.html
or these:
https://www.canadiantire.ca/en/pdp/...ery-cable-4-gauge-0110961p.html?rrec=true#spc
Or similar. 4gauge wire with bolt on ends. No longer than needed (The longer a wire is the more resistance it has, resistance = heat, therefor the shorter a wire of the same gauge is the more current it can carry).

Find a factory mounting bolt or stud near the strut tower/inner fender frame and ad one end of the ground strap to it. Locate a mounting bolt on one of the heads or the block or the transmission and add the other end of the strap to it. Ideally if you connect one end to the battery ground terminal loop bolt and bolt the other end to the transmission it will have the shortest and most direct ground current return path to the battery.
 

·
Registered
Joined
·
3 Posts
Discussion Starter #3
Thankyou for your detailed response I will look in that direction and see what comes of it.
 

·
Registered
Joined
·
167 Posts
Hello I am new here I have a 1997 MX6 2.5 V6 I recently installed a timing belt the engine runs smooth but very predictably when the engine is at full heat it will buck very hard approximately 3200 rpm every time. The car does not want to surpass those rpm. But when the engine is cold it can rev too close to 6000 smoothly. This makes acceleration almost dangerous as the engine almost stalls until i back off the gas and drop below 3200 -3500. I thought maybe injector fuel pressure regulator. Any advice?
I had a similar problem with my 1994 MX6, LS 2.5V6 5 speed. I would agree with checking for good ground wire(s). In my case, I chased this problem for months. Finally, I replaced my 12 year old Magnacore ignition wires with NGKs and the problem disappeared forever. Ignition wires were the last thing I expected because Magnacores are suppose to be high end. They were great wires, but 12 years is asking a lot from any ignition wire set.
Hope this might help.
 

·
Registered
Joined
·
2 Posts
Hello I am new here I have a 1997 MX6 2.5 V6 I recently installed a timing belt the engine runs smooth but very predictably when the engine is at full heat it will buck very hard approximately 3200 rpm every time. The car does not want to surpass those rpm. But when the engine is cold it can rev too close to 6000 smoothly. This makes acceleration almost dangerous as the engine almost stalls until i back off the gas and drop below 3200 -3500. I thought maybe injector fuel pressure regulator. Any advice?
Hi FernDog,

MX6 lover from Australia. My 1995 MX6 2.5L V6 had exactly this problem. It took me weeks to work out how to stop the 3000 rpm bucking when the temperature reached normal operating temperature.

I read the manuals thoroughly with respect to what controls the fuel injection system and the variable intake manifold solenoids. I found that the engine temperature has a lot to do with both of these important systems.

On that basis I questioned the operation of the water temperature sensor. My vehicle has 285,000 kms on the clock so I thought that perhaps the sensor had failed or was faulty.

I purchased and fitted a new after-market sensor. ( AUD 36.) The problem disappeared !

Mazda part no. B593-18-840A

The sensor is no.25 in the picture attached.
 

Attachments

1 - 7 of 7 Posts
Top