Transmission Won't Cooperate With Cali Smog Test

[carlsbadGN]

Not sure whether to post here or in the smog forum but here goes. I’m due for a smog certification in southern Cali. Removed or disconnected all the alcohol related items and returned the vehicle to stock condition, with the exception of the air intake, adjustable FP regulator, and TT emissions chip.

While driving in city traffic to the testing facility, I noticed the car would bog down and shake like crazy at about 25 MPH. The problem would go away if I slowed down or increased speed to about 35 MPH. Also, would clear up if I lightly depressed the brake pedal, indicating that perhaps the TC was locking up just after the shift at 24-25 MPH. As far as I could tell, as soon as it shifted to third gear, the TC locked and bogged every thing down. Not wanting to chance failing the smog test, I cancelled the test.

As I recall, I had the same problem 2 years ago during the last smog test. The tech pulled it down to second gear and completed the 25 MPH portion of the test. The car passed then but the numbers for NO (PPM) were very high.

I have used this TT emissions chip since 2006 and passed with flying colors until the last time.The only changes made were that the torque converter was changed out shortly before the last smog test and the transmission front pump was overhauled by a local transmission shop with GN experience (Donnie Wang at DRW Transmission in Santee.

The car runs fine with it's TT alcohol chip installed but throws a fit with the emissions chip. Anyone ever had this experience or any insight into what is causing the problem with the transmission?

 

[bison]

Your last paragraph answers your question. Maybe the chip has a weird lockup parameter burned in. Unplug the 4 pin connector for the test. Then plug it back in after. Don't drive long distances with the plug unplugged. If oxides of nitrogen are high then your egr circuit is compromised.

 

[carlsbadGN]

Your last paragraph answers your question. Maybe the chip has a weird lockup parameter burned in. Unplug the 4 pin connector for the test. Then plug it back in after. Don't drive long distances with the plug unplugged. If oxides of nitrogen are high then your egr circuit is compromised.

Thanks very much for your reply, Bison. According to Eric at TurboTweak, the emissions chip is based off the stock chip. The stock chip is programmed to lock the converter at a relatively low speed in 2nd and 3rd gear. In 4th gear its programmed for a higher MPH, because the RPM's would be too low in 4th. Just seems odd that the chip worked fine for the first 3 smog tests but almost fell apart on the last smog test.

Eric could program another emissions chip for me with a higher MPH lockup in 2nd and 3rd gears to alleviate the shuddering problem but he isn't sure what effect that would have on the 25 MPH portion of the smog test. Bison, do you think a higher RPM lockup speed would have an adverse effect on the test?

 

[bison]

In the past I noticed much lower emissions with the engine rpm a little higher. Leaving the converter unlocked will probably let it free rev a little on the dyno and free rev will help get the cat converter hotter and less emissions. In CT i used to get cars through with hollow car converter. I'd request the test be done in 2nd gear and I'd run in open loop with lower fuel pressure and retarded timing. I always made sure I had some EGR flow to keep the cylinder temp down

 

[carlsbadGN]

In the past I noticed much lower emissions with the engine rpm a little higher. Leaving the converter unlocked will probably let it free rev a little on the dyno and free rev will help get the cat converter hotter and less emissions. In CT i used to get cars through with hollow car converter. I'd request the test be done in 2nd gear and I'd run in open loop with lower fuel pressure and retarded timing. I always made sure I had some EGR flow to keep the cylinder temp down

Thanks a bunch, Bison! Your input is very much appreciated.