Changed spark plugs and now getting misfires

Pretty interesting, the red flag is all was fine till the plugs were changed. Guess I would go back and retrace all the steps, literally remove the plugs again & reinstall... make sure one of the plugs didn't get cracked on the install etc.

 

Actually, he changed them because of misfires along with the fact that they were overdue. A logical decision. But now he has more misfires on more cylinders. So, I would tend to think that either he damaged all the plugs, or the original problem is getting worse.

Edit to add: Oops! I was going to hang up. Sorry.

 

Missed that, sorry, guess I better hang up too!

 

Off topic, but your avatar cracks me up.

 

What hump?

 

It's hard to stay away.

 

A simple thing to try is to disconnect and reconnect the 12V battery. This will reset the ECU and may help it adjust to the new engine parameters due to the new plugs.

Question: At what warmup stage are you getting misfires? Reference: http://techno-fandom.org/~hobbit/cars/five-stages.txt

Also - how's your corrosion level on the connectors to the spark plugs? May benefit from some good cleaning and a generous amount of dielectric grease.

 

SIGH.
Dielectric grease is an INSULATOR.

It is intended to be packed around connections AFTER THEY ARE PLUGGED TOGETHER........NOT on the connecting surfaces before they are put together.

 

Cops are bad. It's a 10 year old car. The rubber boot on the cop has been around burning hot metal for years.
You rip it out and it's not happy,

At the very least you need to inspect the rubber boot very carefully and hold it up to the sun and look for pinholes.
Then you have the spring in the bottom that's been compressed for 10 years and then you rip it out.
It's a maintenance item. Probably the most problematic thing in modern cars. That and a sooty throttle body or IAC
Prius has no IAC one less thing,

I bought 4 new oem cops so when I change my plugs it will be be done once and be good for another 100k miles. An old cop will drive you crazy.

 

Old cops drive me crazy! But they are usually nicer than the younger dumb ones.

 

This is the stupidest car forum ever.

 

A little fun is the spice of life..

 

I can't argue with that.
A good example is people who insist on using TLAs (Three Letter Acronyms) without explaining what it IS upon the first use.


P.S. And the Coil On Plug assemblies are the modern equivalent of spark plug wires and boots.

 

Often there is a serious gap between engineers and common folk.
We definitely appreciate engineer insight but this forum is the the benifit of common folk who are not necessarily mechanics nor have automotive degrees. Common folk are good at thinking out of the box.

In my field I too forget everyone doesn't know what I know and use everyday and it's easy to think little of them, however they usually excel in an area I'm void and I need and depend on their expertise.

Why forums are great! We all benefit from the whole!

So far I'm thinking there was a problem that was fringe being a real trouble spot and the manipulation of servicing aggravated it....

Would definitely be a good rule out to look for pin holes "against sunlight or very bright light" for abnormalities in anything not replaced.

Watching an engine in pitch black can also reveal issues tiny sparks and shorts, "at least in the old days", prius may be different.

 

did you replace them with oem plugs or el'cheapos
if he taps the coils with a screw driver handle when running is might tell him what one is bad, it will say ouch
is the blinker fluid full?
has the air in the tires been replaced with fall blend?

 

Yeah, in a Prius, the only place for tiny sparks and shorts will be down in the spark plug wells where you can't see them; though you might see some carbon tracks or other signs on the ignitor bodies when you lift them out.

I wouldn't worry so much about the little springs inside. When you're talking 20,000 volts or so, "delivering the electricity" really isn't much of a problem. The bigger problem is making sure it doesn't get delivered where it doesn't belong, so the advice about checking the rubber boots is probably where I would focus.

One thing I've thought about, but never tried, is getting a set of cheap aftermarket ignitors just to see if their rubber boots will fit on the original OEM ones. I suspect the actual electronics in the OEM ones are reliable for a good long time.

-Chap

 

Dielectric grease, while an insulator, IS supposed to be placed directly onto the plug connector, inside the boot and even on the OUTSIDE of the boot to help prevent water and dirt infiltration into the sparkplug well. It is also commonly used on external engine connectors in highly corrosive environments to help protect them from the elements. Doing this AFTER the connection is made is not recommended in the service literature of any OEM.

RTFB

To address the OP's question, the most common cause of misfires on engines equipped with Coil On Plug (COP) systems like the 1NZ are bad sparkplug boots! The HV will leak right thru them to the valve cover/head, especially if they are dirty or damp.

Boots are cheap, get a set. Could the coils be bad? Yes, given the number of Gen2 cars on the road and VERY low reported failures of COP modules, it is incredibly unlikely that you have two, much less 3 or 4 bad ones. If it was an early '00s Ford, well, buy a set of 8

 

Boots are integral to the electronic coil. It's all one piece the boot and the coil I have never seen a coil on plug That consists of 2 pieces. So I have no idea what your talking about get a set of boots there cheap.
Please show me a coil on plug assy that has a separate boot.

An misfire issues on a g2 motor are very common.

 

I made you go find out what the word cop meant. It's a really common term for coil on plug.
Then you tell me what the word cop means. Thanks I had no idea.