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| Exhaust smell / o2 sensor http://classiccamaroclub.mfatw.com/viewtopic.php?f=5&t=4326 |
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| Author: | 78 Camaro [Tue Feb 17, 2015 11:52 am ] |
| Post subject: | Exhaust smell / o2 sensor |
I guess without smelling the exhaust fumes it's hard to diagnose over t'internet but the exhaust has always smelled and i've noticed it more so recently as i've been de-icing the car while it's running in the morning, then i'm walking around and scraping the windows and it leaves a bit of a stank on my clothes and hands. I guess it's unburned fuel? Happens all the time, even when warmed up, if i'm sat at traffic lights and the wind brings the fumes to the front of the car i notice it, quite a strong / bitter / unpleasant smell. It does have an aftermarket exhaust, no cat (looks like a high flow cat box, but beleive it's empty), stock headers but from the headers it's stainless to the back, with dual boxes, has a nice moderate sound. I noticed when changing the heater hose that there was no o2 sensor plumbed in, just the plug end of the wire hanging there. I wonder if plumbing in an 02 sensor would make a difference? Or if it could be something else? Thanks in advance! |
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| Author: | NeilTheCop [Wed Feb 25, 2015 4:45 pm ] |
| Post subject: | Re: Exhaust smell / o2 sensor |
The O2 sensor only makes minor corrections, this sounds like a major rich mixture problem. Pull a plug or 2 and see if they are black |
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| Author: | 78 Camaro [Wed Feb 25, 2015 5:25 pm ] |
| Post subject: | Re: Exhaust smell / o2 sensor |
Hi Neil, Got a couple of pics here from the plugs that i replaced about 3 months ago. Replaced them all, smell is the same before and after. The plugs seemed ok but i wouldn't class myself an expert lol. Is there a way of adjusting the fuel / air mix on an EFI engine do you know? Cheers! Ray  
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| Author: | Yappy [Wed Feb 25, 2015 7:30 pm ] |
| Post subject: | Re: Exhaust smell / o2 sensor |
This how I see it. If you have no O2 sensor fitted the car will run in a default mode which is normally richer then normal. If you can fit an O2 sensor I would do it, you will also notice better fuel economy. I had a friend who had a jap import car and when he had his exhaust replaced by some back street garage the original O2 sensor did not fit(different threads), so they left it off and plugged the hole. The car stunk until I managed to get a sensor fitted. |
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| Author: | 78 Camaro [Thu Feb 26, 2015 11:34 am ] |
| Post subject: | Re: Exhaust smell / o2 sensor |
Cheers Yappy, I have a list of service parts to order for it (belts, hoses, stat etc.) so i'll add an o2 sensor to it and a bung to weld in with it. Hopefully that will help, or at least reduce it to some extent. I'm sure my colleageues will appreciate it when getting in the lift first thing in the morning lol. This looks like the ticket http://www.rockauto.com/catalog/moreinf ... 442&jpid=3 Any idea what / how i can find out what the thread is? I'll need to weld in a bung, so not sure what size look for. Maybe this will work? (i have a stainless exhaust, hence the 316): http://www.ebay.co.uk/itm/316L-Stainles ... 0999&rt=nc Starting to put the parts list together, hopefully be able to sort it sometime in March, will update once ordered. Thanks, Ray |
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| Author: | Yappy [Thu Feb 26, 2015 7:41 pm ] |
| Post subject: | Re: Exhaust smell / o2 sensor |
If I remember correctly it should be the same size thread as a spark plug but pleas don't quote me on this  2 things to take into count. 1. You have headers fitted so the headers will run cooler then the standard ones, this may effect the O2 sensor as it relies on the exhaust fumes to get it up to operating temp, and it won't be effective until it is up to temp. There are self heating heating sensors which you can retro fit these normally have 3 wires, one as the sensing wire and the other 2 are for positive ignition power and one as an earth. There is info about this on the net. 2. Make sure when fitting the plug it is in the right position, if you mount it further down the header tube it might not be as effective. I am sure there will be info on the net again. I think that it lol |
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| Author: | 78 Camaro [Thu Feb 26, 2015 8:21 pm ] |
| Post subject: | Re: Exhaust smell / o2 sensor |
Thanks for the advise, i was actually looking at the difference earlier as there were a few options for heated o2 sensors. I forgot to check the wire and plug earlier, so will check it tomorrow, i'm pretty sure it's a 1 wire plug at the mo. Probably should have been a bit clearer about the exhaust - it's stainless all the way from the back to the headers, but the headers are the standard log ones that are original to the car, they still have the AIR pipes plugged into them (tried to remove the AIR pipes, that's a story in itself lol). So yes, the manifold log is stock, then the stainless system connects to the manifold, it goes into a Y collector behind the engine, off to the side a bit. I was thinking of installing a sensor a few inches into the Y, to ensure both sides of the exhaust had a chance to mix but it was close enough also to the engine. Effectively it would be position inline to the inside of the wheel. I will take a pic, and also try to find the stock mounting position. I think you're right about it being 18mm, that's what i seem to be finding in generic search results but i am yet to find official confirmation about it when it comes to GM related info. Thanks! |
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| Author: | NeilTheCop [Sat Mar 07, 2015 4:00 pm ] |
| Post subject: | Re: Exhaust smell / o2 sensor |
I misunderstood. I assumed you were talking about the engine on your signature, Edelbrock carb etc. What engine do you have? |
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| Author: | 78 Camaro [Sun Mar 08, 2015 12:31 pm ] |
| Post subject: | Re: Exhaust smell / o2 sensor |
Ah sorry Neil, you didn't misunderstand - i probably should update the signature as I have 2 lol, the 79 Camaro has the Edelbrock carb, the 87 Trans Am has the 305 TPI. It's the 305 TPI that has the sensor disconnected (no sensor hole in the exhaust as it's aftermarket) and is the one with the exhaust smell. Haven't started the 79 in 2 or 3 years  but i have put oil through the spark plug holes and turned it by hand with a wrench. I actually plan on cranking it today via the starter for the first time in years (no fuel in the tank, just want to keep the engine and oil moving). Hope that helped!
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| Author: | jon_buss [Mon Mar 09, 2015 7:11 am ] |
| Post subject: | Re: Exhaust smell / o2 sensor |
I haven't replied to this before as I don't actually have an answer. However, your car doesn't sound altogether different from mine which has the standard log headers and then a full aftermarket exhaust from header back. Mine has a full dual system with no cats, but did have the air system welded back in (despite there being no cats to heat up, which is now removed) and the sensors welded back in. To be honest (I may be wrong) I thought the O2 sensor went into the standard header on the drivers side. I certainly have a sensor here, and when I've looked at aftermarket headers some say they have the mount for the sensor (which I'm assuming is the O2). However I also have a sensor half way along the exhaust (roughly underneath the storage in the centre console), I think this may also an O2 but is the 'after' sensor while the header one is the 'before' sensor? With this setup my car smells rich when I first fire it up / it's cold. However the smell goes once warm and the MPG isn't that bad (actually got 26 on a long run, but recently with all the short journeys and work I've been doing it was 15.6). It was much worse, but I had bad injectors and it was only running on six so I don't think that's your problem thankfully  I do have the factory service manual (for a 1991 model) which has some diagnosis steps in. I can have a look tonight and let you know if that helps? Sorry I can't give you any proper answers, but thought my setup 'may' help you diagnose it. |
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