1996 J30t SMOG issue.

[The Other Steve]

Hello.

I have a 1996 J30t. The car is typically driven once or twice per week, about 4K miles per year, about 85K miles total so far. It's been a very good, trouble-free car.



I do oil changes twice per year, June and December, but for several years, no other service except top-off fluids and clean the air filter since (1) it's driven so little and (2) I've had so much trouble finding a service shop familiar with the J30, and also been so disappointed with the ones I've tried. (The last shop I was in for an oil change, I told the Service Writer that the car is driven 4K per year and hasn't had anything except oil changes in a couple of years. So what services would he recommend for this car? He suggested a bundle of services that he said he had worked out from an aircraft maintenance schedule and pre-flight check list. I didn't ask him jet or prop, and I also didn't return.)

I'm in California. The car has been tagged with a "High Emitter Profile". Here are the results from its previous SMOG test:

15mph
HC
measured=44; max allowed=49
CO
measured=0.08; max allowed=0.47
NO
measured=0

25mph
HC
measured=21; max allowed=33
CO
measured=0.04; max allowed=0.44
NO
measured=0

The car has been called for a SMOG test this year.

1. Any suggestions about the car's poor SMOG test performance?

2. What's a reasonable bundle of services (timing, plugs) to do on the car? With the mileage I do, the 90K service is still two years away, for example.

Thank you.

[fourdrinie]

Looks like your J30 is looking like my 97 looked last year. I am in northern CA too.
I had to replace both my catalytic converters last year...
Looks like yours are on the way out as well, they just deteriorate over time and stop cleaning up the Hydrocarbons.
If you fail, you will need to go to a Gold Smog station to have your cats tested...
Sorry to say, it's not a cheap fix...

[driverdriver]

Have you been driving the car with the required premium gasoline or the cheaper stuff? My J30t is older then yours, is only driven during the non snow/salt season and still aces the Ontario emissions test (which is pretty strict).

[The Other Steve]

Thanks to you both for your replies.

Premium gasoline only, always.

The catalytic converter. Yes, it's interesting you mention it, because I have on occasion thought that the exhaust smells suspicious.

[The Other Steve]

Oh yes, forgot to mention, have a contribution to the J30 FAQ: Movies. The J30t appears in 2 Days in the Valley I believe. Believe Charlize Theron picks up Teri Hatcher from the Police Station in a white/ivory J30t. I'll see if I can get a screencap.

[The Other Steve]

In case anyone else has a similar issue, the conclusion:

Changed the oil, then paid the dealer $150 to perform an engine/emissions diagnostic, including a test of the O2 sensors and catalytic converters. In their smog "pre-test inspection", HC tested at 48 ppm against a max allowed of 49. "Low efficiency from catalytic converters bank1 and bank2" was the conclusion, and the tech cleaned the throttle body. No other issues were found. Estimate for replacement of both catalytic converters: $1133.86.

While in line at the smog test station, I sat in the car with my foot on the accelerator, revs to 2500 for the 15 minutes I waited. HC tested at 12 ppm (compare above at 48 ppm). The car passed, easily.

[J30tChumpCar]

Good deal, nothing like a bit of heat to burn those extra HCs up!

[fourdrinie]

I dont understand, did you 1) replace the catalytic converters or 2) just clean the TB and heated up the cats while waiting?

[The Other Steve]

^ #2. just cleaned the TB and heated up the cats while waiting

[driverdriver]

I take my J out for a good long highway drive before an emission test.

[The Other Steve]

Yes, it's what the service writer and tech recommended. Right before the test, long drive on the highway.

The problem (at least it seemed to me) was that none of the smog stations would take an appointment, and there was no way to tell how long the car would sit waiting (on the day I went, outside in the rain) before it was tested. I figured the best bet was just to go, sit in the car and keep it idling at a freeway rpm.

One other thing, in case anyone does have a similar issue: I had it tested on a full tank of gas. I don't know if/how much it matters, but my expectations were that I was going to be fighting for every last HC point, and I recalled in the past someone telling me that below a quarter, you could be sucking up debris that had accumulated in the tank, which could marginally affect the smog result. We're also on "winter blend" gas here in CA, and the car is always tested this time of year, in December. I wonder if it makes a difference to the HCs.