So I bought my firebird about a week ago. I got it smogged and it failed. NOx to high. So heres what I've done

I pulled off the EGR valve to check it. I bougth a vacuum bump and it held pressure. Next I checked the passages for clearance for the gases with a coathanger and it was free. Then I noticed the other line by the vacuum line (the little plastic brittle one) was broken where it connects to the solinoid AND at the throttle body. I bought some tubing today and some adapters and fixed it.

I plugged all the stuff in and fired it up. It ran different and I was getting vacuum on the EGR. It was no vacuum at no throttle, then tap the gas and it opens way up, but if i just increase throttle slowly, there is no pressure. the car runs smoother, smells better. However I can still here a vacuum leak (a small one) coming from under the throttle body. I've checked the lines above it and none leak. Intake Manifold Pressure is at a steady 15 inches. is the noise I hear coming from the butterflys in the throttle body? Before i get it smogged again, I may just replace all of the vacuum lines, but if this vacuum leak is only the throttle body I wont. Should I completely replace the lines

Yes it will be a bitch job and take some time. Thanks

 

TTT

 

They can't all be bad. Just inspect/ pinch each one and find the bad one/ ones. Check the brake booster too.

Once ya get the EGR to function right, your car should pass.
Should not flow EGR at idle or full throttle.
But flow at part throttle cruise. Be sure the timing is not over advanced. Less timing will reduce NOX too.

 

If you fail agian after that replace the cat.

 

Yeah, and if you fail agian (sp?) after that replace the injectors. And then the spark plugs. And then the wires. And then every sensor on it. And then the heads. And then the shortblock.

:lala:

Or...jump into the DIY_PROM forum and learn to read the ALDL data to find out what's really going on in there, so you can find and fix the actual problem.

 

thanks for all the help guys - i'm pressure sure the EGR is functional now. I'm gonna give it a vacuum test again before next test. The timing is 10 degrees. The specs say 6. Is that allright?

Also I'm getting a cat efficency test done before next test.

The engine idles rough but it runs smooth when running above 1000 rpm. THe idle bounces a little - a smidgen actually - and it sounds like it has a cam - the mufflers amplify that. I do get a cough when I'm going 2000 rpm or above and push in the clutch to idle - a cough coming out of the single chambered flowermaster. Im told by my friends that this is normal from the flowmaster - but I don't believe it. Are these 2 related? What should I do? I was going to do a full tuneup and replace radiator, waterpump, all the coolant lines, all the vacuum lines, and clean up some engine parts. How often do these engine mounts go bad? Also will my rough idle stop with new plugs/wires/rotor/distributor? Any other tips? How rough do your cars run at idle? Ok thats it - bye!

 

Not if it has a cam. You can get it to run smoother by adjusting the idle up some but that isn't like a catch all fix.

 

Put your timing back to 6, 10 is out of spec for passing smog unless the tech just doesn't care. After you pass, just put it back to where you had it.