×
ScannerDanner Premium Customer Support (15 Mar 2019)

Please add This email address is being protected from spambots. You need JavaScript enabled to view it. as a contact in your email system. I am having a very hard time communicating with some of you because my reply messages are ending up in your spam folder! So please check your spam folders too!

× Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!

Downstream O2 sensor voltage drops durring acceleration Normal?

  • Drunken Elvis
  • Topic Author
  • Offline
  • New Member
  • New Member
More
13 May 2019 09:06 #29597 by Drunken Elvis
2.2 litre 06 Chevrolet/220,000 miles, has had a P0420 code come and go twice in the last few weeks.
There is a slight possibility of a minor exhaust leak 12 inches after of the second O2 sensor. Car runs very well.

I have a simple scan tool but it is not capable of storing live data so I cannot post a graph of what is happening. The up steam O2 sensor fluctuates as normal.

Question is...
I was watching the live data while my wife drove in the city and when under acceleration the voltage from the down stream O2 sensor would drop to .1 volts for a second or two. Normally it was fairly steady at around .7 volts but not when accelerating. Is this normal or the sign of a worn CAT? Faulty down stream O2 sensor?

Please Log in or Create an account to join the conversation.

  • Chad
  • Chad's Avatar
  • Offline
  • Moderator
  • Moderator
  • I am not a parts changer.
More
13 May 2019 10:13 #29602 by Chad
ALL O2 sensors should go FULL RICH during WOT. If they don't, you have a fuel delivery problem, or a bad O2 sensor.

Someone correct me if I'm wrong. :)

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."

Please Log in or Create an account to join the conversation.

  • Chad
  • Chad's Avatar
  • Offline
  • Moderator
  • Moderator
  • I am not a parts changer.
More
13 May 2019 10:15 #29603 by Chad
An Exhaust leak near the O2 sensor could be suspect, too.

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."

Please Log in or Create an account to join the conversation.

  • Drunken Elvis
  • Topic Author
  • Offline
  • New Member
  • New Member
More
13 May 2019 10:18 #29604 by Drunken Elvis
When I say accelerate, I mean mild=mid acceleration, not WOT. The second O2 sensor voltage drops to .1 volts at this time.

I have had my hands all around the exhaust and cannot fine a leak but the wire mesh around the flex pipe is partly missing. So I suspect a minor leak.

Please Log in or Create an account to join the conversation.

  • Chad
  • Chad's Avatar
  • Offline
  • Moderator
  • Moderator
  • I am not a parts changer.
More
13 May 2019 22:00 #29632 by Chad

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."
The following user(s) said Thank You: Noah

Please Log in or Create an account to join the conversation.

More
14 May 2019 07:21 - 14 May 2019 07:23 #29637 by guafa
Hi drunken,

You can check for a exhaust leak by restricting the out of the pipe.

One person can do it for you and you can hear the gases going out through the leak
Last edit: 14 May 2019 07:23 by guafa.

Please Log in or Create an account to join the conversation.

  • Drunken Elvis
  • Topic Author
  • Offline
  • New Member
  • New Member
More
14 May 2019 09:48 #29639 by Drunken Elvis
That's not a bad idea. I was thinking of hooking my shop vac backwards [blowing] into the exhaust pipe but Im afraid of pushing debris into the cylinders. I was really asking if O2 sensor voltage normally drops when applying moderate throttle. I have searched for videos of the live data and I find examples where the voltage signal drops and some videos where the voltage rises. Makes no sense to me.

Also considering performing a propane enrichment test to gauge the condition of the catalytic converter but I don't have the best equipment for that. The P0420 has not come back for a while but if it does, I'll have to investigate further.

Please Log in or Create an account to join the conversation.

More
14 May 2019 14:04 #29646 by guafa
Well, i was testing a fixed car and paying attention to your request.

When mid aceleration, when upstream went rich (let's say 0.7v), downstream followed same voltage. Sometimes a little bit lower (let's say 0.5v).

Never downstream went to 0.1v

Please Log in or Create an account to join the conversation.

  • Drunken Elvis
  • Topic Author
  • Offline
  • New Member
  • New Member
More
14 May 2019 14:57 #29648 by Drunken Elvis
Thank you for the information. My wife drives the car every day so I don't get many chances to look at it and it's been raining here a lot lately. I'll have to do more examination. Perhaps an exhaust leak.

Please Log in or Create an account to join the conversation.

  • Tyler
  • Tyler's Avatar
  • Offline
  • Moderator
  • Moderator
  • Letting the magic smoke out since 2011
More
15 May 2019 10:16 #29664 by Tyler

Drunken Elvis wrote: That's not a bad idea. I was thinking of hooking my shop vac backwards [blowing] into the exhaust pipe but Im afraid of pushing debris into the cylinders.


I'm actually OK with this idea. :cheer: I use a rubber cone and an air pressure regulator connected to shop air for the same purpose. Very handy for finding leaks without having to run the engine, and for checking repair welds for pinholes.

To answer your first question, it certainly sounds like a catalyst issue. Manifolds and flex pipes are also suspect on that engine.

Please Log in or Create an account to join the conversation.

More
18 May 2019 16:47 - 18 May 2019 16:48 #29775 by Deltron
You need a graphing scanner that you can either watch live or record. You want to record the front sensor and the rear sensor at the same time as well as TPS or speed, some way to mark the location of snap angle changes. What you do is cruise along at 50mph or so and then instantly let off the gas. Watch your O2's at that spot. A healthy cat, the rear o2 will jam itself lean a few MS after the front one. If the cat is bad, they will simultaneously jam lean.
Last edit: 18 May 2019 16:48 by Deltron.

Please Log in or Create an account to join the conversation.

More
19 May 2019 02:34 #29788 by Jasondo
Tyler would you be able to show us exactly what you use for exhaust leak testing and where you got them. I like that idea.

Please Log in or Create an account to join the conversation.

  • Tyler
  • Tyler's Avatar
  • Offline
  • Moderator
  • Moderator
  • Letting the magic smoke out since 2011
More
19 May 2019 10:23 #29805 by Tyler

Jasondo wrote: Tyler would you be able to show us exactly what you use for exhaust leak testing and where you got them. I like that idea.


I bought one of these, but any brand will do:

www.amazon.com/OTC-6522-10-Leak-Tamer-Adapter/dp/B00KIL0P0Q

Added an air regulator to the hose end with a worm clamp, and a gauge. :) Stuff the cone into the muffler end and add some pressure.

One warning: It's possible to add a LOT of pressure to an exhaust system this way, which can 'create' leaks that otherwise wouldn't be there under normal operation. Take care to add a reasonable amount of pressure (5 PSI-ish).
The following user(s) said Thank You: Jasondo, Dtnel

Please Log in or Create an account to join the conversation.

  • Not Allowed: to create new topic.
  • Not Allowed: to reply.
  • Not Allowed: to add attachements.
  • Not Allowed: to edit your message.
Time to create page: 0.694 seconds