steve40th

Well, I took the Vette out for a spirited drive and I decided to do a little run. Well, the car was throwing black smoke out for 2-3rd gear to redline, approximately 6200 rpm today.
Well, the last time I saw this much smoke was during a dyno day where I was running excessive black smoke and was down 25rwhp from the last dyno ran with this combo.
Before I dive into getting data, later today, let me say what I know was changed by me that I did have problems with. The heated O2 sensors. I , not the builder of the heated O2 sensor harnes, pulled a pin out of the right o2 harness and repaired it with a new pin within the connector as it did show a code of a low voltage to right O2 sensor. That code is gone.
I do have an exhaust leak on the right side, but it is after the O2 sensor. It is on the extended pipe that meets up to the Header, DRM headers, and is about 1-2 inches after the O2. Is that too close?
The exhaust flange has no leaks on either side.
The tune is PCMforless and worked great until I changed out the O2 for heated ones. SO I know its not the tune, which was made with ECM data from driving the car via TTS data.
The injectors are fine and dont leak, the pressure holds and is 43psi.
I am all ears guys, what do you think?

STL94LT1

Steve, it could be the tune if the old non-heated o2 sensors weren't letting it go/stay in closed loop. Now that the engine will stay in closed loop, maybe the tune really wasn't that good.


Just a thought.
-Mike

steve40th

Makes sense. I will email Alvin, and will see what I need to do. I didnt realize the sensors read differently, heated and non heated that is.

STL94LT1

Steve, the heated/non-heated o2 sensors don't ready differently. But, sometimes with long tube headers and non-heated o2 sensors the car won't go into or stay in closed loop. This definately make an impact on how the car runs.

bobmic93

I put in the new 4 wire heated O2s and was having problems with the one bank. I put a stock O2 on just the bad side and it cured the problem.

steve40th

Did you put a single wire back in on that side?

steve40th

Before the heated O2's it was not going into closed loop till you were moving, as it was getting cooler when idling. The heated O2's fixed that.
Maybe I need to fix the exhaust leak real quick, if I can, then re log the Vette, and send it off to Alvin for a look-see.

STL94LT1

steve40th

Okay, I tightened the exhaust as much as my torque wrench allowed, 110ft/lbs on the straps, 2 3/4 inch stainless steels from Napa.
Alvin is very good, so I am thinking it is the exhaust as the rest of the car is tight and ignition is new as I hardly drive it, and the DELTEQ fires right up and goes. It idles in gear pretty darn good too with a slight hint of fuel, as opposed to what it was with the original tune and unheated sensors (tearjerker).

steve40th

Okay , did some TTS datamaster on her and the right side is definitely showing a need for fuel. SO, I see that the O2's are workign fine, cycling very well. The right one goes into the low 900 milivolts, and the left high 800 milivolts at WOT.
The injectors on the left go to about 85-90% duty cycle while the right goes eventually over 100%. SO, the right has an exhaust leak somewhere. I was thinking of swapping the O2's, but they are working fine.
I am going to redo the right exhaust flange, even though I see nothing coming out (exhaust etc, and no burn marks). I will do a patch job as best I can on the right where the slip fit pipe mates to the headers.
Then I will try to doa temp fix with High temp sealant or something to try to temporarily fix the leak, or if it looks feaseable, seal it with new exhaust clamp or whatever. I can solve this.

steve40th

Okay no exhaust leak near the O2 sensor. The leak is on the back clamp where the Flowmaster meets up.
I put a smoker in the bung and watched for smoke to come out anywhere on my header or the flange etc. NOTHING.
Is it possible the O2 is just bad, without throwing a code?
I know I can swap sensors.

5abivt

Check your plugs

FD2BLK

Pull the O2 and inpect it to see if it is smashed in any way. The reason I state this in on my stainless works LT's I ran into a problem with my rightside O2 using the bung in the header. In my case I was able to move the O2 to the rear O2 sensor (The 94 has a rear O2 but the ECM will not throw a code for it) and plug the fron O2 hole in the header.

steve40th

Well, I went under and put smokers in the pipes via the bung hole (that doesn't sound right ) then I couldn't find anything so I changed the sensors from left to right. Well, now it ran very well. I have the data logs if anyone wants them to see before and after.
I am still confused as even though all I really did was swap O2s, unless loose, I am still skeptical about this. And my idle went up. HMM

bobmic93

Yes, on the passenger side I put the single wire back in and just driver side is a heated 4 wire O2. This cured my problem after H/C and header install. I was looking for intake and exhaust leaks and couldnt find any.

steve40th

These speed density's are very sensitive apparently, or are they? At WOT what is the computer reading, O2's?
I will keep checking it randomly. I am very skeptical that swapping cured this. But maybe it did.

Alvin

That is incredible unusual. Did both O2's report the same? Any chance there was a error in teh connection?

steve40th

I think the connection was bad/loose as it has been running very well. No ill smell of fuel, staying in closed loop. The O2's were dead nuts on after one run, as if the computer caught up, after the O2's were swapped.
Haven't had a chance to rerun/datalog the car, but haven't needed to.

Alvin

Good to hear.

Oil is a Major culprit when looking at harness connector issues.