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[Jason@SportsCar]

Originally Posted by Bluevitz-rs

Then are you running a different ECU? Or have you modified the signal going to the ECU to make it think there's a cat?

Because if the cat has been taken out with a stock computer, it'll set a code every time.

That would be a different code.

[Bluevitz-rs]

The missfire could be caused by the cat delete. The reduced backpresure could be the cause. The ECU could be retarding the timming due to the code and that the lack of power.

[Jason@SportsCar]

Originally Posted by Bluevitz-rs

The missfire could be caused by the cat delete. The reduced backpresure could be the cause. The ECU could be retarding the timming due to the code and that the lack of power.

The cat does not show up on my list of possible causes.

[Bluevitz-rs]

You have to think of it this way...

... with less back-pressure you get more exhaust out of the cylinder on the exhaust stroke, but the intake charge is still the same on a N/A motor. (ok, not EXACTLY the same due to valve overlap and the effect that has on pulling in air, but basically the same.) The intake charge will be "cleaner" than what a stock ECU is programmed for. The stock A/F ratio is based on the back-pressure being there and the amount of residual exhaust gasses still left inside the cylinder on the intake stroke.

A very simple cheat to make the ECU run richer is to trick it into thinking the engine is colder that it really is. If you add a resistor to the Water Temp Sensor and make the ECU think the engine is only running at 110°F or so it'll think it needs more fuel for running in the cold weather. (this might also set a code for the thermostat, but it's nothing major.)

Another method is to add a resistor to the intake temp sensor in the MAF meter. You can trick it into thinking it's sucking in air at -40°. This should have the same effect, but with less chance of setting a code.

[Jason@SportsCar]

Originally Posted by Bluevitz-rs

You have to think of it this way...

... with less back-pressure you get more exhaust out of the cylinder on the exhaust stroke, but the intake charge is still the same on a N/A motor. (ok, not EXACTLY the same due to valve overlap and the effect that has on pulling in air, but basically the same.) The intake charge will be "cleaner" than what a stock ECU is programmed for. The stock A/F ratio is based on the back-pressure being there and the amount of residual exhaust gasses still left inside the cylinder on the intake stroke.

A very simple cheat to make the ECU run richer is to trick it into thinking the engine is colder that it really is. If you add a resistor to the Water Temp Sensor and make the ECU think the engine is only running at 110°F or so it'll think it needs more fuel for running in the cold weather. (this might also set a code for the thermostat, but it's nothing major.)

Another method is to add a resistor to the intake temp sensor in the MAF meter. You can trick it into thinking it's sucking in air at -40°. This should have the same effect, but with less chance of setting a code.

This issue is not cat related. Thanks.

[CTScott]

Are you running the stock drive by wire throttle body, or is it upgraded to a cable throttle? If it's still DBW, going into limp mode is indicative of a failure of one of the two APP (accelerator pedal position) sensor circuits.

[Jason@SportsCar]

Originally Posted by CTScott

Are you running the stock drive by wire throttle body, or is it upgraded to a cable throttle? If it's still DBW, going into limp mode is indicative of a failure of one of the two APP (accelerator pedal position) sensor circuits.

Yes, still DBW. And it does seem to be in limp mode.

[Jason@SportsCar]

Test day pics:

[YarisSedan]

LOL if i didnt know what HP means for SCCA i would look at your car at quick glance and it looks like your advertising your car has 51 horsepower.

[markitect]

Guys, he knows what he's doing

If it started when he was almost out of gas then there was probably gunk floating on top of the fuel which has now clogged the fuel filter, fuel pump or an injector(s).

Although with it being only one cylinder I would probably rotate the injectors around and see if the misfire moves, before I pull the fuel pump/filter, but I also have an interior in the way.

Good to see it on the track!!!!!!!!!

[Jason@SportsCar]

Just to eliminate it as a possibility, and so we don't have to do it later, we are taking the fuel injectors and pump to RC Engineering this week to have them tested and cleaned. One less thing.

[kngrsll]

i thought about putting a 89.5 wHP sticker on my rear bumper just to rub a little more salt in the wound :)

[Jason@SportsCar]

Originally Posted by kngrsll

i thought about putting a 89.5 wHP sticker on my rear bumper just to rub a little more salt in the wound :)

I started with 5 HP (last digit of the VIN), but someone in the same race group had 5 reserved, so they asked me to change it.

It is all temporary anyway... Once the new graphics are done it will have a number that is significant to Toyota's racing history.

[Loren]

Um... did you put new plugs in?

I've put more than a few track miles on my Yaris and the only misfire problem I ever had was due to the factory "100,000 mile" iridium spark plugs.

Replaced them with a set of plain ol' parts store NGK's, problem solved.

I got two different codes from this problem, and at least one "shut down" that happened 2-3 times, but didn't set a code. Apparently, when the ECU detects repeated misfires (such as when I graze the rev limiter in 3rd coming out of turn 17 at Sebring), it just says "NO" and goes into limp mode until you cycle the ignition.

So, if you haven't already, put a new set of plugs in it.

[Jason@SportsCar]

Originally Posted by Loren

Um... did you put new plugs in?

I've put more than a few track miles on my Yaris and the only misfire problem I ever had was due to the factory "100,000 mile" iridium spark plugs.

Replaced them with a set of plain ol' parts store NGK's, problem solved.

I got two different codes from this problem, and at least one "shut down" that happened 2-3 times, but didn't set a code. Apparently, when the ECU detects repeated misfires (such as when I graze the rev limiter in 3rd coming out of turn 17 at Sebring), it just says "NO" and goes into limp mode until you cycle the ignition.

So, if you haven't already, put a new set of plugs in it.

We have not yet, but we will be replacing the plugs and coils while we are waiting on the injectors. Better to have it all fresh.

[Loren]

If you shotgun everything, you'll never really know what the problem was or which of your spares are actually good parts.

Troubleshooting 101: Change one part at a time.

[Jason@SportsCar]

Originally Posted by Loren

If you shotgun everything, you'll never really know what the problem was or which of your spares are actually good parts.

Troubleshooting 101: Change one part at a time.

Spares are not used parts. At some point it will all be new, so might as well get this stuff out of the way.

Change one part at a time if you want to take a week. Replace it all with good stuff right off the bat, and hopefully you never touch it again.

If I had a spare motor I would just put it in, God knows what was done to this thing when it had FI. But I don't have a spare, so we will just wait till there is a break in the season for a proper build.

[cali yaris]

such as when I graze the rev limiter in 3rd coming out of turn 17 at Sebring

name dropper