Multiple cylinder misfire under boost

[LtNoogie]

Several months ago at an autox event, while under boost the Yaris posted a CEL and went into limp mode in the middle of the race. The codes showed misfires on multiple cylinders. Fortunately, the CEL cleared and the car ran fine if I stayed out of boost.

When I pulled the spark plugs, they were all coated with a dry reddish deposit. Today I put in a fresh set and the car runs as well as it did right after the blower was installed. The SC typically puts out 7lbs of boost. I use Shell V-Power gas at 91 octane.

What causes this type of deposit? The plugs are NGK BKR7EIX Iridium with a heat range of 7. The plugs have been in since December of last year.

I'm also running a set of 1ZZ injectors. AFR stays at 14.7 under normal driving conditions and then goes to 11-12 under boost.

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[scape]

fuel with additives

[LtNoogie]

Maybe I'll try someone else's 91 octane for a year and keep checking the plugs.

[thebarber]

isn't 14.7 a bit lean?

[yaris-me]

It looks slightly rich, which is because of the 11-12 AFR. The deposits probably cause the misfire and replacing the plugs is the best thing to do. Probably best to replace plugs on a regular basis.:smile:

[cali yaris]

Ten months on a boosted car is pretty long for plugs. I would check them more often.

What is the gap?

[LtNoogie]

What? Replace Iridium plugs every year or sooner? If I'd known that owning a S/C was this expensive, I... just kidding.

Thanks for all the suggestions. It's running great with a new set of Iridiums.

Not to save money, but I'm going to Harbor Freight to get one of those spark plug blasters. I've always wanted to see how well they work.

[LtNoogie]

Noogie that would be from octane booster or fuel additives. My plugs looked similar to yours.

Mike, what kind of gas do you use. With enough data points we can show what brands of gasoline leave what kinds of deposits. I've been using Shell V-Power exclusively. I put in one can of octane booster every other month on race day.

[yaris-me]

Not to save money, but I'm going to Harbor Freight to get one of those spark plug blasters. I've always wanted to see how well they work.

If I'm not mistaken you'll also need an air compressor. If you buy an air compressor, buy one with enough capacity to run air tools, like paint gun, impact wrenches, etc... Then I'll come over and work on my car. :biggrin:

[cdydjded]

Red to purple deposits on one side of the core nose are an indication of a fuel additive. While many of these deposits are non-conductive and do not contribute to lack of performance, some fuel additives contain octane boosters that leave conductive deposits on the core nose. Care should be taken to select fuel additives which are compatible with ignition systems and do not contain conductive materials such as octane boosters.

[LtNoogie]

If I'm not mistaken you'll also need an air compressor. If you buy an air compressor, buy one with enough capacity to run air tools, like paint gun, impact wrenches, etc... Then I'll come over and work on my car. :biggrin:

I have such an air compressor. Let's plan a weekend to work on your car. :smile:

[yaris-me]

I have such an air compressor. Let's plan a weekend to work on your car. :smile:

:laugh:Just Joking. I only need to do electrical work right now. :smile:

[cali yaris]

Race day? Did someone say race day? :biggrin:

[N3misiS]

Interesting, I just Turbo'd my car, there is a post...
It is good to know as I am also runing NGK Heat range 7 but the spark plugs are for the
1krfe 3cyl....

As far as I know fuel aditives is a no no, the cr*p they put in there is unbelivable sometimes, here is South africae we are quite lucky we can choose 93, 95, and 102.6 octain fuel for race day....

Have a look at my post, I found some stuff maybe worth mentioning.