Mazda B2500 Misfire

[nashlaw]

I have replaced one of the coil packs, changed plugs and wires and still getting misfires on #4 cylinder. On the computer, it only says "misfire #4" and does not give the cause.

Motorheads, do you have any ideas? My mechanic is stumped.

 

[lazy21]

Re: Mazda B2500 Misfire

I had a multiple misfire code once, did all that you've done. It ended up being a vacuum leak.

 

[GUNNER75]

Re: Mazda B2500 Misfire

Got compression?

 

[The Mechanic]

Re: Mazda B2500 Misfire

Got to go to the basics. I will assume it is about a 2000 since it is the 2.5
First things first as said before, check compression. No more than 20% difference or it is cylinder head or motor time. As said before also a vac leak can defiantly cause this. Do you have a scanner? If you do have your mech check the "freeze frame data" this will tell you when the misfire is happening. Example is if misfire is at idle look for compression, vacuum leaks. If misfire is at higher rpm than look toward valve-train, fuel supply, ignition breakdown. If all the time look at ignition, injectors, very low compression 20% or more.

I'll throw a few more at you AFTER the basics. Have been seeing some fuel contamination issue in the last year where a small amount of water gets in the fuel rail and you will get a misfire on a back cylinder (accel) or front cylinder (decel)

Tip. Good way to check for intake leaks is cold engine (gaps are bigger cold) start and idle, squirt or poor water everywhere at a controlled location and controlled rate. You will notice that the misfire will go to a dead miss as soon as you poor the water over the exact spot.

Without a good knowledge of scan tools it is difficult for me to help to much more as looking at the data stream usually is all I need to do to tell what is wrong.

 

[nashlaw]

Re: Mazda B2500 Misfire

Thank you for the responses. I was told by "The Parts Store Guy" that one coil pack ran 2 cylinders(both exhaust and intake). The repair man also thought that. I went to another repair shop and the fellow said this was wrong. From what he said, one coil pack ran the exhaust and one ran the intake. So, I changed the other coil pack and things are 100% better. I still have a mis, but nowhere near as bad as before.

Where should I check for a vacuum leak?

 

[The Mechanic]

Re: Mazda B2500 Misfire

Actually they are both wrong or possibly you misunderstood them. The system is known as a waste spark. Old school coils had a low voltage side (battery) and high voltage side (coil wire). I will oversimplify but as you add power at a low voltage to the first winding you (charge the coil) at the moment you remove power the magnetic field collapses and induces (makes the magnetism and voltage) go to the second coil. It will have a lot more turns of wire thus increasing the voltage (a bunch like as in taking 12 volts and jumping it to 30 or more thousand volts 30Kv.

Modern ignitions will use both sides of the coil to produce a spark and will fire one coil two times in your system. One on the power stroke and one on the exhaust stroke. It will at times help ignite any possible emissions left in the cylinder before the cat.

You need to check for vacuum leaks any place there is a vacuum line. Also you need to check at the spot that the intake manifold bolts to the cylinder head. I happen to use a propane torch for this as propane is safer than using carb cleaner. (torch is not on fire just a stream of gas) this will cause an increase in idle speed when you find it. I don't recommend you do this as it is not for shade tree diag.

You did not mention whether the misfire was at an idle, under load, power braking, or hard accel.

 

[The Mechanic]

Re: Mazda B2500 Misfire

Forgot to add most modern ignitions are significantly more than 30Kv now. Many run in the 60Kv or more. Use to be we would have fun and see who could take a coil wire in the hand while cranking over the motor (bet I lost a brain cells and fucked up some sperm doing that) I could go for a while. But modern ignitions can actually hurt a bit. For someone not used to it, it will shock the krap out of you. So be real careful if the motor is running. I can remove a coil or plug wire as the motor is running to check for good coil output.

You never got back on whether compression was good

 

[lazy21]

Re: Mazda B2500 Misfire

who's the baddest? ^ that guy!

 

[The Mechanic]

Re: Mazda B2500 Misfire

Funny thing is when I was first dating my wife she told me a story how she got surrounded by some guys that were a little rough around the edges and she pulled out her stun gun. I told her that it may have scared these guys but not to totally rely on it to "stop" someone coming after her. She laughed and said "just one quick jolt would knock any man to the ground and that's where he would stay until he woke up" Needless to say I grabbed her purse pulled it out, pulled the trigger and as it was hissing and snapping away I pressed it against my right thigh. Don't get me wrong it did not feel good at all but I gave myself a good 5 seconds (felt like an hour) and as it is shocking me I asked her when I should fall down. She almost shit herself.
I have always wanted to give the tazer thing a try because I really do think I could take several steps during its getting up close and personal with me.

 

[lazy21]

Re: Mazda B2500 Misfire

Who's the kinkiest mofo you know now? ^ that guy!

 

[Yeticowboy]

Re: Mazda B2500 Misfire

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Mechanic</div><div class="ubbcode-body">Funny thing is when I was first dating my wife she told me a story how she got surrounded by some guys that were a little rough around the edges and she pulled out her stun gun. I told her that it may have scared these guys but not to totally rely on it to "stop" someone coming after her. She laughed and said "just one quick jolt would knock any man to the ground and that's where he would stay until he woke up" Needless to say I grabbed her purse pulled it out, pulled the trigger and as it was hissing and snapping away I pressed it against my right thigh. Don't get me wrong it did not feel good at all but I gave myself a good 5 seconds (felt like an hour) and as it is shocking me I asked her when I should fall down. She almost shit herself.
I have always wanted to give the tazer thing a try because I really do think I could take several steps during its getting up close and personal with me.

</div></div>

Trust me the Taser is a whole different ball game over the stun gun. It actually pulses at a frequency that interrupts the nerve signals that control your skeletal muscles. A proper hit with taser probes will make a person involuntarily "plank out". Your whole body becomes stiff as a board and you just fall down.

Stun guns are just painful and most people can fight through those pretty easily.

 

[The Mechanic]

Re: Mazda B2500 Misfire

Still want to give it a shot, or is it a shock.