GT failed AirCare, need advice.

The only answer to a plugged muffler is to replace it. You really can't "clean" it out.    On a cost basis, trying to get a shop to replace your Fiero muffler will cost you as much in parts and labor as just buying a complete exhaust system from one of the major vendors like the Fiero Store or West Coast Fieros.   

When you do get the car through, please post up the Air Care results.

Here is the breakdown on my 88GT. I am really worried about taking it in next week.



And here is the last time it went though.

Its my idle hydrocarbons.   I believe when the motor was built they installed a performance cam, however they decided to set the cam in with extra advance. Which in a carbed motor would be great, would allow the motor to make much more high end power, however the car idles poorly, and is hard to start cold due to the lower cranking compression. To add insult to injury, With the stock intake, the motor does not breath well enough to even take advantage of the mod.

I had to lean out the mixture a lot in order to get it to pass the 2nd time around.

Ah well such is life.

I just installed the stock ECM and stock Chip back in it and will try it next week. If it fails I have a new catalytic converter here to install.

Okay, I understand. Thanks Chay.

I found this image of the inside of a Fiero muffler. Looks like lots of places for debris to get stuck.

Well, it's stopped raining. Guess I should crawl under the GT today to see if I can figure out what's going on.

 

Pictures as promised...

With all the symptoms I had observed (and with Chay's helpful comment about a possible "air blockage"), I suspected it was the muffler that was plugged (from the contents of the previous cat) because the current cat looked to be in such good shape from the outside.

Here's the top:

 

 

Here's the bottom:

 

Here's the outlet: (A little difficult aiming the flash down 10 inches or so of pipe.)

Notice how the "honeycomb" looks really good.

Are you now ready for the money shots, two pictures (with slightly different lighting) of the inlet?

Have a good look at why my GT was running so bad!

Remember what I was saying earlier in this thread about a fine white dust?

Patrick wrote: When I was re-doing my ignition components a few days ago and revving the engine by hand while at the back, it seemed to me that I could see fine white "dust" of some sort flying out of the exhaust tips. Hmmmm.....

Well guess what poured out of the outlet (through the intact honeycomb) when I tipped the cat on its end? Yep, you guessed it - a fine white dust! I wasn't hallucinating after all.

I sincerely doubt that this very fine powder would plug the muffler. My fingers are crossed however that the previous cat didn't send chunks of its innards into the muffler.

I think I lucked out as this appears to be the best-case scenario. I can probably beat the rest of the honeycomb out of this cat and then just put it back on. Won't even have to bother buying a straight pipe.

Edited by Patrick

Here's the entire contents of my cat in the bottom of a bucket...

I put the gutted cat back on and started her up... What a difference in sound! 

Didn't get a chance to drive the GT yet after getting the exhaust back together. However, judging from the sound, it should go a heck of a lot better.

While I had the cat off, I took the opportunity to have a look at my front exhaust manifold from underneath. Well, I found the reason for the slight "tick, tick, tick" sound coming from it. The bottom bolt is broken off on #2 cylinder.  That's a chore for another day (next spring).

Next step is going through AirCare again. That'll probably be next week. Reports to follow. 

Edited by Patrick

CFoss wrote: After running it for a while it'd be interesed in seeing another log file to see if the blms numbers get back to around 128.

You bet. Yeah, I'm interested in learning what the numbers should look like when the engine is (hopefully) running normally.

 

Just want to add that last night was the first time since I unplugged the cat that I was able to take a decent run on the freeway (to the club meeting). Quite a difference in power!

The biggest surprise was that club members in the parking lot thought the GT was "quiet" when I pulled up.  ....

 

I got an informative PM from Chay (CFoss) regarding my WinALDL log. Much appreciated!

I've copied it here so that others might gain from his knowledge.

CFoss wrote: Hey there. I looked at it. It looks much better to me. At idle, the ecm is still compensating for a rich setup, having the blm at 120 still. The good news is that it seems to be successful there, as you notice the 02 readings are varying from low readings to high readings. This means you are in a band around stoich and it's probably ok.The low readings indicate a lean condition, leading me to believe that the fuel is within the ecm's capability to control.  When the throttle is off idle, the blms are consistent around 132, which means the ecm is richening the fuel a bit (128 is the balance). This is a huge change from when the cat was plugged. I'd take a shot at air care. You may still have too much fuel at idle, but it should show marked improvement and then you can contine from there if need be, because that would be conclusive proof you are on the right track.

Could any of you perhaps explain what's happening with the INT readings between 150 and 200. It demonstrates the same behavior elsewhere, but it's more noticeable there. What is actually going on when it peaks like that?

Edited by Patrick

CFoss wrote: This is some black magic eh?

Yeah, that's for sure.

Thanks Chay, I appreciate your feedback.

In This thread I reported that I'm only getting 15.5 mpg, mostly city driving.

Is it reasonable to be expecting a lot better gas mileage than that if everything is performing as it should, especially considering I am NOT racing around?