Piston Slap: To Love A Sienna Like No Other? (Part II)

Piston Slap: To Love A Sienna Like No Other? (Part II)

TTAC commenter MatadorX writes:

Sajeev, I wonder if you wouldn’t be able to offer some of your wisdom on the continuing saga of the van.

The new automatic went in and worked perfectly. The engine got fully rebuilt. New crate short block direct from Toyota, heads rebuilt-surfaced/valve job/adjusted/stem seals. Entire engine re-gasketed with Toyota FIPG/OEM gaskets. New pretty much everything else on the front of the car. Wires, plugs, all three O2 sensors (Denso), IAC, Coolant Temp sensor, MAF, resealed injectors, OEM fuel filter. Brand new main TWC catalytic converter. Converted both the exhaust manifolds to 1998 Sienna California emissions spec (integrated warm-up cats), so now the car has a total of THREE catalytic converters.

Broke in the entire setup for 1,000 miles the proper way with varying RPMs, letting off gas to allow rings to seat, and occasional three-quarter throttle bursts, special break in oil for the first 500, then over to Mobil1. Tons of power, smooth, quiet. At idle she is so smooth you can’t even tell the van is on. Checked the entirety of the engine for vacuum leaks — nothing. Compression is strong across the board. Zero blow by.

However, I live in California, and — you guessed it — the van still failed the smog check.

I am failing HC Hydrocarbons at 25 miles per hour, and barely passing at 15 mph. Other emission categories are actually fine. My best test:

15 mph MAX: 47 ppm, MEAS: 47 ppm
25 mph MAX: 31 ppm, MEAS: 49 ppm

As you can see, the standards are incredibly low for my specific vehicle which came new in 1998 with 1994 technology: one cat three feet from the engine, no EGR, old-school heated O2 sensors (not A/F ratio sensors), wasted spark coils, and no VVT-I. Most vehicles are a pass if under 70 ppm here, or below 200 ppm for any other state. I have tried warming the car as hot as possible before the test, using 91, 89, and 87 octane (no real difference between those). I even tried the denatured alcohol trick, which had ZERO effect on my numbers — it just raised my NOx. I also tried one higher heat range plugs, but again the numbers actually got worse.

If I had to guess, the engine is pretty much already as healthy as it is ever going to be. I am about out of options. Registration lapsed four months ago (paid, so no penalties but can’t get my tags). I think the only thing I could do would be find a shop to rent with a dyno/exhaust gas analyzer, and pay the best tech they have to mess with it to try to get it through. This is pretty much the nuclear option, as the cost would likely run into the $1,500-2,000 range, according to estimates I got. Honestly, as far as this has gone, I would be willing to spend that if I knew 100 percent that this could make it pass, but finding the right shop with expertise in SoCal that wouldn’t laugh me right out of the place with the stock minivan would be nearly impossible.

Nine-tenths of shops here, if they are any good, require you to convince them to work on your car, which is honestly why I became such a competent shade tree.

I love my van, it has immense sentimental value to me, and I am willing to do what I have to in order to register it. I just want my baby back. I scored an amazing deal on a leftover 2015 XB 5MT the dealer really wanted gone in May. Basically, I should be able to sell it used for around what I paid new within two years if I keep it under 20,000 miles — so at least I have something to drive to work with a warranty for just the cost of reg, tax, and gas, but it just isn’t the same as the “fat” Toyota quality of the 1990s.

Any feedback you or your readers could offer would be very helpful, especially as relating specifically to California smog.

Sajeev answers:

This takes me back to the sadness/frustration felt when my Mark VIII wouldn’t pass emissions.  I did everything to make it pass Texas’ low and high speed dyno emissions test.  It always failed the high speed test, until a savvy muffler/speed shop said my RandomTech cats have a unique internal shape that performs poorly under 1500 rpm, which was my problem (third gear, 1100 rpm, 25 mph) at said high speed test. So I locked that sucker in second gear and all is well!

Immense sentimental value in mind, you and me seem to be cut from the same cloth! So let’s spitball some ideas:

  • Is your rear (aftermarket) cat the same basic design?  You never know, maybe testing at higher RPMs at those speeds might help!
  • Replace any soft/brittle/cracked vacuum lines under the hood
  • I want to say you should check fuel pressure but that might just be me reading ahead.  So without any further ado… 

MatadorX concludes:

Figured I’d send an update: she finally passed! Flying colors.

It ended up being something to do with the fuel pressure regulator and pump, two of the few things I didn’t replace on the rebuild, but did at the end just to make sure all bases were covered. Also went over to a California spec 3 catalytic converter setup, with the front two coming from a donor car (huge money new) and the rear main an aftermarket unit that is Cali legal. Pretty much no emissions, according to the final test sheet. Happy to have the van back again. Thank you for the tips/encouragement!

 [Image: Toyota]

Send your queries to [email protected] Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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