Iron Duke TBI smog fail - AGAIN

Well, fixing the vacuum leak didn't solve the problem. The DMV referred me to a special diagnostic shop.

What we learned: yes, the EGR diaphragm is leaking. However, plugging off the vacuum doesn't change the symptoms.

HC starts out normal, then randomly goes REALLY high. Then it will go back to normal, then really high again. CO stays normal and within range throughout the test.

The tech wasn't willing to say for certain whether the fact that the EGR won't hold vacuum was the culprit.

Then I had to go to work. Will return Sunday for more help.

In reply to EvanR:

fuel pressure? O2 sensor working properly?

My Iron Duke Fiero had no EGR, and it had no O2 sensor. I'd replace the IAC and the TPS, and make sure the throttle cable isn't loose anywhere, or hanging up on something, or even check the linkage on the TBI to make sure one of the bushings aren't loose. Have you checked the butterfly in the TBI to make sure it works properly?

Normal CO and high HC is misfiring, or running very lean.

I'm sure any emissions repair shop worth a damn already knows this, though.

Knurled wrote: Normal CO and high HC is misfiring, or running very lean. I'm sure any emissions repair shop worth a damn already knows this, though.

Most useful info I've gotten thus far. Will look for more vacuum leaks, and delve further into the ignition system.

Thank you.