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Can't pass smog with brand new engine!

1998 Toyota Sienna 1MZ-FE v6

Owned the van since new, just completed a full mechanical overhaul of the van.

Crate short block engine from Toyota
Fully rebuilt heads
OEM gaskets
New Catalytic Convertor
Entire coolant system
Entire timing system
New OEM IAC, PCV, MAF, FPR, Coils/wires/plugs, fuel pump, temp sensor, injectors cleaned, all 02 etc, etc

Basically everything under-hood is new, including most all additional non emissions parts (Rebuilt transmission, all mounts, entire steering system, entire suspension system, charging/starting system, A/C system, etc)

Engine properly broken in with break in formula oil, according to manufacturers specs. Oil exchanged for full synthetic after 1500 miles.

Have tried several times unsuccessfully to get the car to pass smog. It passes in all categories by a wide margin except for HC (Hydrocarbons).
California wants it to run up to 49 ppm @ 15 MPH, and a 31 ppm @ 25 MPH. I have only managed a 47ppm/49ppm, failing the 25 MPH test.

I’ve tried different grades of fuel, vehicle is 100% warmed up prior to testing with 30-45 minutes of driving.

Compression is perfect. Car has plenty of power, and idles so smoothly you can’t tell it is on.

No check engine lights, all readiness monitors set.

Pretty much out of ideas.

Have thousands into the repairs of this van, and due to the incredibly low standards for passing may not be able to register it here in the future.

You may have answered your own question, sadly.

High HC comes from a rich condition or from incomplete combustion or from oil in the combustion process. A rich condition should be covered by the ECU’s control of the injectors and measured by the O2 sensor. Incomplete combustion would likely be from a weak ignition. Oil in the cylinders is a possibility of leaking valve seals or rings as well as a badly functioning crankcase evaporation system. It sounds like you’ve covered everything in the rebuild. What is the oil consumption? Have you replaced or re-built/cleaned the evap system? Look for excessive oil use and excess oil residue inside the intake manifold from the evap system.

I need to ask, though, why did you spend this much and work this hard on an 18 year old Sienna?

Where did the Catalytic Convertor come from?
Is it CARB approved?

I was thinking something similar, and I wonder if the spark timing or valve timing might be off.

are all the parts in the new install correct?

I got a shop van from another location, and could not get it to pass emissions- with an engine that wasn’t even 2 years old- in southern Arizona, where testings isn’t overly stringent. My issue, after spending months and months of searching, was that when the new engine was installed, the wrong fuel injectors had been put in, which were over fueling. The ECM was trying to lean the fuel mixture out, but just could not.

Take it out on a empty road, get it up to the lowest speed in its highest gear. Then add as much throttle as you can without the transmission downshifting. Accelerate to at least 20 mph higher but not more than 30 higher. Repeat 10 times. Then test.

One more thing, just about every spark plug has several heat ranges. Your OEM plug is a Denso PK20TR11 or an NGK BKR6EKPB11. If you are not using one of these, then switch to one of them. Assuming that you are using the correct plug, the 20 in the Denso and the 6 in the NGK part numbers is the heat range. Try the identical plug in the higher heat range. PK22TR11 or BKR7KPB11.

Thanks for the reply’s

Inspecting the plugs at 1k miles, and all look as new, no oil deposits, etc.

Compression both cold and hot was tested, numbers are all very even, in the high 180s-190psi

No oil consumption over the 1500 miles I’ve driven the car. Without tags it is tough to rack up any more miles. Ive been using one day trip permits.

Crank evap system fully reconditioned. New OEM pcv, hoses. Valve cover PCV baffles disassembled, all parts hot tanked, and reassembled. No oil cap pressure is felt running, neutral pressure as this engine should be.

Any the expense was great, but I did almost all the work myself, that way I could ensure everything was done correctly with top tier parts. Every single component on the rebuild came either directly from Toyota, or a Toyota OEM supplier, nothing but made in USA/Japan components. The few seals, etc that came in with other countries of origin were tossed in the trash and replaced with OEM.

Convertor is CARB approved, was burned in prior to testing for a few hundred miles. Nice and hot when tested.

Timing belt is OEM, aligned precisely with all new OEM components. Timing light is bang on. Car has just as much power as it did fresh out of the box, no stumbling/bogging. Starts instantly. Idles perfectly. No smoke.

As far as correct install, anything is possible. However I took my time with rebuilding the van, approximately 9 months working in my spare time. All procedures were as set forth in my copy of the official Toyota sourced repair manual for my model/year van.

Injectors were cleaned/balanced and were the originals. The car has been in my care since new. However, I am leaning towards just replacing them all with brand new Denso units, however the $700 cost gives me pause.

Plugs are the PK20TR11 OEM dual electrode units. I also tried one higher heat range to see if it made a difference. The HC numbers actually went up so they were removed.

Are you still using the old exhaust system. You have put enough miles since the rebuild that it should not matter but I was just wondering if it might be picking up residual hydro carbons left over from before the rebuild.

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That doesn’t mean that you shouldn’t try adjusting the timing to address your problem. If you retard the spark timing just a bit, you might reduce your unburned hydrocarbons.

But is it OEM?


Then test what?

Smog test.

and what would it indicate if the numbers improve? Just asking to learn. Obviously, that’s not what the OP can do at the emission test station to pass.

The hard accelerations at low RPM seat the rings better. Its a old school trick. The go to the test station to see if it passes.

At this point, I’d be inclined to go to a different test station too.

I would spend a little time looking at the fuel system

Tee in a gauge, since I know that engine doesn’t have a fuel pressure test port

Fuel pressure okay at idle?

Then do an injector balance test . . . maybe one of the injectors is flowing too much

What are your fuel trims?

Bank 1 short term
Bank 2 short term
bank 1 long term
Bank 2 long term

I’d be curious to know what the fuel trims are at 25mph, when the HCs are too high

If the new cat is a cheapo cat . . . even if it is CARB-approved . . . I wouldn’t expect it to be as effective as an OEM cat

If I were you, I would NOT mess around with the ignition timing . . . although I thought it wasn’t adjustable on this model year and engine

If it IS adjustable, and you mess around with it, you WILL fail if the guy is supposed to check ignition timing and actually does check. Any smart smog guy WOULD check, because any car could potentially be a “sting” car sent by the CA BAR or whoever monitors the smog guys

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Vacuum hoses come to mind, a vacuum leak could be the issue.

It has been my experience that a vacuum leak will have an effect at idle, but not 25mph

I know your downstream O2 sensor is new, but I suspect that is where the problem is. You may have a defective sensor or more likely, the connector has gotten some corrosion or other contamination on one or more of the pins during the rebuild.

Well today I am pleased to announce my 1998 Sienna PASSED!!!

1ST of all went to a different shop for the test. Didn’t like the vibe at the other one.

2nd. I figured out that when I had thought I replaced was the fuel pressure regulator it was just the fuel dampener on the rail. So I went in and put a new fuel pressure regulator in the tank. I have no fuel pressure symptoms, starts easily and plenty of power, but maybe too much fuel? I scored a new surplus OEM Denso USA one for $45 on eBay so what the heck.

The final numbers? Pretty much perfect. Ran “0.00” %/PPM in all three important categories. Now this is the result I expected out of all new everything. Very happy to have my beloved van back again. Has to be the cleanest 1998 Sienna in the country now. Especially with the ODO of 229,000 haha

15 mph…14.5…0.1…49/7/0…0.62/0.03/0.00…501/90/0
25 mph…14.5…0.1…32/6/0…0.75/0.03/0.00…754/84/0


Congratulations! Hard work pays off. So does tenacity.

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