Hello, my first post here so here goes.

I got a 89' GTA and shes running bad. Ive had her for mabye a month or two. My cats were plugged so i just got headers and choped em off. I changed the O2 sensor and fuel filter and the MAF sensor(160$ wtf?) I changed the wires and the plugs when i first picked it up. recently changed the cap and rotor.Air filter is clean.

She has always ran rough at idle only stalled on my a few times but shakes when im just slowing down to a stop (it not my rotors). The rpms go up then fall back down then it goes back up and falls back down while im sittin in park.

I had the MAF code but i changed it and then i got the o2 sensor code after i changed that so when i put my headers on I put a new 02 sensor in and that code went away. Now I got the 33 code.
-MAP sensor signal voltage was too high (low vacuum)

Now when i did my headers the plugs where like black from it running to rich.

question # 1 where do i look too now????????????
question # 2 from it running rich before could i have foiled out a few plugs?

p.s. ive searched and couldnt really find an answer to my questions.Thanks in advance!!

EDIT: its got a 350

 

Welcome Aboard!

Run the procedure to set the throttle minimum air position, clean the IAC and throttle body, and set the TPS voltage. Check your base timing, and inspect for vacuum leaks and a leaking EGR. The '33' error code is likely related to the TPS voltage being set incorrectly.

 

Check your fuel pressure. Also check the vacuum line that runs from the fuel pressure regulator to the upper plenum. See if its sucking fuel. Happened to me because the diaphram was torn and sucking fuel. Ran horrible. Let me know
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Oh yea. check the egr valve. Get a vacuum pump and suck it open at idle. See if it runs rough/dies. Also hook a vacuum gauge to it and see in it holds around 18in/hg at idle and steady. This will give you a good idea what condition the engine is in.

 

From what I read sounds like you have made some changes to the engine. Did you reprogram your PROM to compensate for the changes. If you didn't, this is where alot of your trouble is. The car will run like a pile of crap, it sucks!

 

Definitely symptoms of running rich, the idle surging in particular....usually vacuum leaks will cause a lean condition..... Definitely check the fuel pressure reg as blown suggested.....

 

It wouldn't be a bad idea to check the vacuum line at the FPR for leakage, but that doesn't explain the '33" error. Also, as soon as the error is set, the ECM will default to Backup Fuel Mode, which is considerably more rich than normal Closed Loop Mode.

Further, with no cats installed, the exhaust is going to smell rich even though the mixture may be "perfect" - You old guys remember what that smells like?

 

Very true....

And I'm not old, but I know that smell very well....there are 4 cars, including mine, on my culdesac, all making between 300 and 600 hp, and none have cats....

 

will leave the whole taste, feel, smell method to the old school. We have five gas machines and ossliscopes now.

 

We had 3-gas analyzers and oscilloscopes back then, too. Every Sun 920 and 1120 had them, and they worked well. My point was that the well-trained nose can probably detect an over-rich condition without the need of an analyzer, but if he was thinking it was rich, it may actually be due to the different (old-school) exhaust aroma with the cat converter missing, while the mixture is actually just fine.

 

I think you got my meaning. He may only think it's rich because of the different exhaust aroma.

That's cool. I've got five cars, all making 1,050HP. One makes 90, one makes 195, one makes 260... You get the idea. 300-600 between four is not all that much to brag about.

Oh - You meant "EACH" making between 300-600HP. That's a little different.