Mazda3 Forums banner
1 - 7 of 7 Posts

· Registered
Joined
·
17 Posts
Discussion Starter · #1 ·
Hey all!

Just took a PERFECTLY GOOD running car and dorked it up....a bit... after a spark plug change at 104K-ish miles. First went after the new (not recommended) Autolite plugs I had just put in.....as lots of posts about using NGK is best. SO, pissed off the Autolites and came up with a set of NGK Laser Irirdium ITR5H13 plugs to reinstall. (Pulled out ITR5F13's but no longer available. the ITR5H13 is the NGK recommended sub.) No change with new proper NGK's......!? Gap'ed them to around .050".....

Car has been largely trouble free but for a trans output sensor that failed somewhere around 60K. No biggie. Synthetic oil changes at 6-8K. Tires and brakes.... But this is challenging me. ECU is throwing no codes to point me.....

Engine runs "growly" now at low rpms when accelerating normally. I thought maybe I had bumped the exhaust system with a wood block that I had used to hold the car up to work on it (oil change).....but exhaust is no where near.... I can definitely hear a stutter or miss in the firing (exhaust note coming thru the firewall..turn down the tunes!) from idle up until you get on it and bring the RPM's up to cruise, then the stutter clears up and goes back to "sewing machine" smooth.

Wife claims it is down on "scoot".....power..... To me.....it seems like the miss goes away after things warm up after a short-medium long drive of say 5-10 miles....... Again, at normal 3K-ish rpms and cruise, I cannot hear any missing.

I'm more of an old school "coil n carb" guy, but I have read up on COP/MAF engines and have owned Ford 4.6 powered vehicles for some time, and am really impressed with the technology, so this engine presents nothing new technically in that regard...... (other than using an INCH-LB torque wrench to install plugs!) :)

HOWEVER I NEED TO ASK: How do you put this car on a scope to see the 4 cylinders/COPs firing to tell you who is being bad??????? Is this even possible or are you supposed to wait for a code..... :( HOW DO SHOPS Deal with pinpointing which coil is "failing," but not totaly dead yet??

I understand the idea of swapping a good coil in place...rotating it thru....and maybe indeed this is the way to attack this, but want to be certain without spending money not needed. Is the only way to check COPs while operating (ie see them on a scope) to simply swap a new COP in one location at a time????? Seems like technology fails to deliver? But that's why I'm asking!

I tried searching this forum on the spark plug threads but got nothing worthy, nor under testing COPs. Figured there would be more....found bad links to shop manuals.....

SO figured I'd ask see if some of the more tech savvy mechanics would have any suggestions beyond swapping plugs again........ I dug the old plugs out of the garbage....as a last resort just to test....could throw them back in!

I don't know how fragile the COPs get in these cars.....but I'm also aware of how to remove them gently as to not stress the wires etc. (I have worked on limited GM products also....ugh!) Made sure I wasn't pulling on the harnesses, popped them off of the valve cover restraints.....

If anyone can shine a lite on this, I'd appreciate it!!! Actually my wife would.......

Cheers!
Steve
 

· Registered
Joined
·
1,585 Posts
My first thought is, NGK does not recommend gapping their Laser Iridium plugs. Hopefully you didn't damage one of the electrodes when you did it. They are very fine and easy to mess up.

Pull the plugs, and carefully look at each of the tips.
 

· Registered
Joined
·
17 Posts
Discussion Starter · #3 ·
theblooms,
Thanks for the comment!

I was certain to adjust the gaps carefully, attending to the ground electrode only. I found the gaps to be off by a few thousandths of each other across the batch.....

My original question still stands......how does one "view" the ignition system firing during operation. This would or should indicate a misfire whether due to damaged plug or failing coil. This info I can hopefully carry forward to working on the Ford 4.6's and more which are gaining more popularity in engine swaps.

Cheers!
Steve
 

· Registered
Joined
·
284 Posts
It is easier than people think to damage a spark plug during installing them. Its also easy to cause a continuity problem between the spark plug terminal and the coil terminal connector.
Gapping (if experienced) with some specialized spark plug types and better to use a gapping tool even the NGK Laser Iridium plugs as long as you do not break or crack the insulator is fine. I think that is what theblooms meant to say about the warning?
I change the gap on most every sparkplug I use no matter the type or brand with very few exceptions.

It is only my opinion but using a .050 gap is to big no matter who recommend it for even a brand new ignition system . I recommend no more then .040(+/- .002 )The Mazda ignition can not fire the plug very well above 3000 rpm with the gap at .050.
 

· Registered
Joined
·
284 Posts
Testing the coils requires either a scan tool plugged directly into the OBDII Diagnostic connector that can read coil active events or an experience induvial using an oscilloscope. My personal preference is generally with an oscilloscope. I do occasionally for fast evaluation will use my Snap-on Solus but for more detail and evet comparing between cylinders its really hard to beat a good old fashion oscilloscope.
 

· Registered
Joined
·
15 Posts
i went to the ngk website directly and got a totally different spark plug numbers (for the 2.0L & 2.3L)

so how did you come up with that plug number, since the site says itr5h13 not compatible?



wow, site's plug gap specs is .052" which are supposedly pre-gapped already
 

· Registered
Joined
·
284 Posts
Pre- gapped spark plugs from the Spark Plug manufacture may not be the gap recommendation by the auto manufacture also may not even be the best gap for an engine. The spark plug gap recommendations given by auto manufactures are based on new engines. As engine get older typically for the highest possible performance from the ignition system and the spark plug altering the gap may be necessary. Generally, this means a smaller gap then when the engine was new.
 
1 - 7 of 7 Posts
Top