I was having a problem with the car idling really high and when coming to a stop the rpms would drop suddenly and it would idle like junk. It was a stuck IAC so I replaced it. I did the normal relearn and the topgun relearn procedures. It idles normal now but it sounds terrible and is shaking the whole car. The exhaust is really loud... REALLY LOUD! Like I've got a cammed big block under the hood, and there is an occasional knock coming the passenger side of the engine. You can hear over my noisy water pump pulley. Whats going on?

http://www.youtube.com/watch?v=xlbYAw5i6zg

The tach isnt right

Couple of ideas:
1. When was the last time you did a top end clean?
2. How old is your 02 sensor?
3. How old is the PCV?
4. the shaking sounds like a bad plug wire...

1. Haven't done a top end clean, but it didn't look bad at all when I had it apart last.
2. It's about 3 months old, but I didn't buy it new. It's a heated o2 off of a 2000ish chevy v6
3. Theres no PCV system hooked up. Both valve covers just have filters.
4. All new plugs, wires... within two weeks actually. Gapped at .030 I swapped working ICM and coils from a 94 prix before winter, but Im losing spark under heavy load (WOT) so I think I have a bad coil again. But Im ONLY losing spark after half throttle or so.

Also... There are no vacuum leaks anywhere and its got new topend gaskets (except the LIM and heads).

Did this start happening right after installing the heated 02?

Its hard to say... I know that we tested the o2 sensor after putting it in. My buddy hooked up a scan tool and we watched it read while we were driving it around. Oddly enough... It would read totally lean when we came to a stop.

Damn I wish mine was that loud :laugh:
But seriously I wonder if the fuel system would have something to do with it. Such as a ruptured fuel pressure regulator or bad injector. I think I'm just guessing. My black TGp does have some similar problems but it still has the stock chip in it. :icon_question:

Its worse now. When I took it out driving last night, It would idle super high but only when moving. In the video you can see it'll rev up when I put it in neutral. When I put it in neutral and come to a stop the rpms will drop suddenly. Also, when cruising for more than a couple of minutes... the SES light will come on for a while and then go off. It seems like the knock at idle is getting worse.

http://www.youtube.com/watch?v=a0FaUStvOCs

AHHH this wasn't happening before :willy_nilly:

Quote from: NTRCOOL on March 16, 2010, 01:10:18 AM
But seriously I wonder if the fuel system would have something to do with it. Such as a ruptured fuel pressure regulator or bad injector. :icon_question:

x2 did you ohm your injectors?

No, but im starting to think the same, that would explain the knock???

What I don't understand is why the computer is keeping the IAC open so much while driving. It'll rev right up to 3500 if i put it in neutral now matter what speed Im going as long as it isn't 0. As soon as I come to a stop the rpms will drop like Paris Hiltons panties.

What I'll bet is happening is there's something wrong with the ECM and it's keeping the IAC open. Then when I come to a stop, the rpms drop suddenly because the ECM is only fueling enough for idle while the IAC is giving enough air to run at 3500 rpms.

That would explain why the scantool showed the o2 reading totally lean when idling and normal when driving. It would also explain the knock. Is there anyway I can test this theory or better yet... fix it?

Got the problem fixed!!!

Here's what happened:

I went over to my friends house to pull out his scantool. We hooked it up and read the code which was rich exhaust. So we started the car and watched the o2 sensor readings. When first starting the car it took only a minute for it to go into closed loop. When it did, it started running a little rougher, the o2 was reading rich. As time went by, you could see the ECM pulling fuel and the car would run worse. The o2 was still reading rich. After about 2 minutes of idling, the car was just barely running and was pinging pretty badly. Then it threw the error code and went back to open loop. It would start to run better, just barely. The first thing we thought was bad FPR. We checked the vacuum line and there was no fuel. We got to talking about it and we knew there was no way that the engine would ping and it would be running rich, so we decided the o2 was bad... even if it was still reading. I went and bought a new one (17 dollar bosch at autozone) and hooked it up quick as I could. Bingo bango problem solved... an idle relearn later and I was good to go.

Thanks EVERYONE!!!!  :icon_mrgreen: :icon_mrgreen: :icon_mrgreen:
I'm learning more and more about this car and finally starting to figure it out. Here's the new exhaust vid... although it doesn't sound as cool as a VERY lean idle, I prefer this to a knocking engine.

http://www.youtube.com/watch?v=9jM4a9kAJTs

Glad it is fixed..........not to rain on your parade but that Bosch is not going to last very long.

My tgp keeps killing bosch ones every other oil change, lol. I work at a parts store and defecting them out and putting a new one in is too easy for me to get a 75$ Delco one.

Quote from: Prospeeder on March 17, 2010, 03:23:49 PM
My tgp keeps killing bosch ones every other oil change, lol. I work at a parts store and defecting them out and putting a new one in is too easy for me to get a 75$ Delco one.

I took out a heated o2 and swapped in the bosch. I don't plan on keeping the bosch... Ill be keeping my eyes open for another heated o2.

Glad you got it fixed now it will be more fun at the track.