Misfire continues after I change the ignition coils and spark plugs

Except, as keeps needing re-pointed-out, that the changes made with 4th gen are largely accounted for by the changed application in 4th gen. The move to a post-cat EGR tap was based on industry-wide research into its different chemistry and effect on combustion, going on during the gen 3 years, and the upsized bores of the EGR plumbing necessarily came with that change: the pressure is lower at a post-cat tap, so the bores already have to be bigger for that reason alone, just to deliver EGR at rates like gen 3. (Which is why G4-into-G3 retrofits that try to use the G4 EGR end up with too much of it.)

One gen 4 change they did make that seems independent of that is coolant nipples now on the valve itself. That may help keep it from getting so hot the ski jump gets mashed.

 

Could there be a corellation between carbon build-up and mashed ski-jump? If the cooler's radiator is carbon-coated, it will cool less efficiently?

I know the 4th gen EGR has improvements, very effective ones apparently, but I'm thinking chauvinistically, having a third gen, and wanting to avoid "issues", I'm employing periodic carbon cleaning.

My main argument in my previous post, was that carbon build up in the 3rd gen EGR happens even if the car is not burning oil. Regardless of who's to blame, who's hands are clean or not, oil burning or not, the 3rd gen EGR system reliably chokes up with carbon.

If there's ever a class action law suit regarding 3rd gen EGR issues (and head gasket failures), a lot of your points would be useful, for Toyota's lawyers.

 

Or the fuel......or both.

 

The fuel is efficiently metered and burned. It has the detergent additives designed to keep the valves clean. Excessive and undesigned for hydrocarbons are overwhelming in this engine. If any combustion based byproducts are contributing, its excessive blowby pushing oil byproducts into the intake thanks to low tension oil rings and a poorly designed pcv system. An experiment in mpg across Toyota models that failed.

(ps I thought Sam had placed me on his ignore list. All good things must come to an end.)

 

Sell it and get a car that you can drive another 200,000 miles...... sold my v to a guy that had to have it.....I bought a matrix with the money.
It had 156,000 on it...... runs perfect getting close to 35 mpg......... and no worn out hybrid crap...........

 

Sure. IF everything is working right.
Sometimes it isn't.

 

I think any exhaust system will be somewhat sooty, oil burning or not.

Again, the EGR components on my ‘10 were accumulating carbon on par with reports here, and I’ve yet to the oil dipstick level budge between oil changes.

 

If that's true, why am I getting EGR restriction test results of 18.4 kPa and above at over 131k miles?

 

What does that number mean? Assuming it means minor flow restriction, it is not aware of inequities in degree of clogging in the intake manifold EGR passages.

but hey: just go by those numbers, see how it goes.

 

Not perfectly, though. All gasoline engine exhaust contains carbon particulate. GDI engines are worse.

 

It means there wasn't much restriction in the EGR cooler yet. "Inequities in degree of clogging in the intake manifold EGR passages" shouldn't have been a factor, because that was soon after I cleaned out the manifold passages.

Try again!

 

It means that during the ECM's last test of EGR flow, opening the valve to whatever degree is used in the test caused the intake manifold pressure to increase by 18.4 kPa, confirming flow. Around 21 or 22 is seen with squeaky-clean systems, and the number goes down with increasing restriction.

Yes, that's been covered before, in pretty much every post where I've explained the test; it's why, even if you are watching this number to keep tabs on upstream restrictions, it is still good now and then to take the intake manifold off and check its passages directly, as they are the only part of the path this number can't tell you about. (And, also, because there may be stronger reason to look for a link between unbalanced EGR flow and engine damage, than one simply between uniformly reduced EGR flow and engine damage.)

It's also worth remembering that this test is not completely specific for clogging; a mashed ski jump in the valve will also pull the number lower. We don't have enough reports yet to tease out, if you have both clogging and a mashed ski jump, how much reduction in the reported number was due to each.

We also have too few reports, still, that combine flow test numbers from the car (which are in kPa and a kind of indirect measurement) with an actual bench test of flow through the same EGR cooler, removed at that stage.

I do still have a cooler here that I removed and had the car's numbers when I removed it, so when I get around to making a bench measurement I can post that and probably be the first one, unless somebody beats me to it.

Until then, the closest we've got is some reports where people held their coolers up to a light and then offered bafflingly precise percentages for how clogged they were.

 

Soot on the cooler fins may not be impeding flow too much, but still it could be reducing its ability to cool (mashed ski ramp?).

I’m not gonna debate endlessly; it’s your car lol. I’d rather over-maintain than leave it late in the day. I think the odometer is a decent gauge as to when it needs cleaning.

 

Makes you wonder how gen2 survived without egr

 

I understood they did EGR through valve timing that retained more exhaust from the previous cycle than conventional timing would. That technique is simpler, but has a different set of drawbacks.

 

All Prii did (still do) that. Gen 3 can even do more of that than Gen 2. From another thread:

Yes, the Gen 1 and Gen 2 variable intake timing can be advanced as far as 18° BTDC on the exhaust stroke, so that a bit of exhaust gas does enter the intake manifold under some operating conditions, and they do even refer to that as "internal EGR" in the New Car Features manual.

Interestingly, they changed the range of timing adjustment between Gen 1 and Gen 2. The most advanced is the same 18° BTDC for both, so they can do the same amount of "internal EGR". They cut back on how far the timing can be retarded: in Gen 1, it could retard as far as 25° ATDC, but Gen 2 can only retard to 15° ATDC. I assume the 1NZ engine used in the c is similar, but I don't have its exact timing specs handy.

Of course the 2ZR-FXE engine used in Gen 3 also has variable valve timing and can do the same trick, even more so: the 2ZR's intake timing can advance as far as 29° BTDC. It can only retard to 12° ATDC. So they've restored some of the adjustment range they took away between Gen 1 and Gen 2: Gen 1 had a total range of 43°; Gen 2 trimmed that to 33°, all by reducing the amount of available retard by 10°, and Gen 3 expands the total range back to 41°, all added back on the side of advance (in fact, reducing possible retard by still 3 more degrees).

So Gen 3 is already able to do more "internal EGR" than Gen 1 or Gen 2, without its external EGR system.

So the added system must be serving one or more other purposes for them, like:

• Allowing them to decouple the amount of EGR from the intake valve timing. Maybe there are some driving conditions where they don't want the valves advanced that far, but still want to use EGR. That's not possible when it's only done by valve advance.
• Allowing them to used cooled EGR. Obviously the "internal EGR" is putting full fresh combustion-temperature exhaust back into the intake. Cooling the gas has benefits. A search for papers on "cooled EGR" turns up the research that was being done industry-wide showing why that's a good development.

 

I understand the cooled EGR and delaying the closing of the exhaust valve to allow higher compression with more open throttle positions to reduce "pumping losses". One of the reasons I bought a higher mileage Prius C versus the larger displacement engines in the 2010 and later models. I thought they were working on using valve lift and camshaft timing to run the engine with a more open throttle position with higher compression, like the 14 to 1 on my C. This helps with partial load efficiency by lowering throttle restriction and using the EGR as an inert gas buffer to use with more open throttle position.

 

I have a 2014 Prius and I had seen this post and had my mechanic check my car and they did a pressure test to determine if it was a head gasket leak and said that it was not that. I have since had the plugs and coils replaced, and the fuel system cleaned And I am still having the problem when it's cold. Any ideas? Was a pressure test sufficient to determine a head gasket leak? I haven't noticed coolant consumption or oil consumption.

 

It can be very difficult to look at a pressure gauge (only) and see the impact of a few drops of coolant being forced through a breached gasket.

The most positive determination is made when you combine that pressure test with a borescope inspection. They thread a tiny camera in through the spark plug hole.

When you do it that way, it's visually quite obvious. You'd see a few CCs of pink coolant dribbling in.

But because the volume of that leakage is relatively small compared to the volume of the entire cooling system, you might not notice the pressure gauge needle tip downward a tiny bit.

 

Mark coolant level with marker or tape.
I have experienced the junk toy head gasket problem like thousands of others.