Smoking after down shifting (Black smoke) All comments welcome!

[97$Cobra]

The car is a 97 Cobra with 43,000 miles. The last owner didn't drive it very much..... I sometimes get a puff of smoke at start up, but, not always. Lately, after getting on it and then down shifting to a stop, it will let out a pretty decent amount of black smoke. I do have an offroad H-Pipe on it without MIL Eliminators.

1. Are my 02 sensors causing my car to go very rich and thus cause black smoke imp2: on down shifts? Would mil-eliminators help this?
2. Did the valve seals maybe go bad from the car being stored for so long?
3. If it is the valve seals, how much in labor would I be looking at to replace them with better than stock seals? I'm in the process of selling my house and I don't want to be tearing into my car...........

Any other ideas? I have not pulled codes as of yet.

Thanks for any responses!

 

[Jrgunn5150]

Offorad pipes tend to that to a small extent, since the cats aren't catching and burning that little bit of fuel that's epelled during a rapid change in engine load. It's not like James Bond style is it?

 

[97$Cobra]

It's a decent amount. A nice little dark black cloud

 

[Jrgunn5150]

I'm pretty sure all you are experiencing is normal offroad pipe behavior. And just so you know, the rear O2's only tell the computer whether or not the cat's are functioning, the front's are the ones that control your A/F ratio.

 

[clobato]

I just bought my Cobra about two months ago. It had an O/X on it when I got it. I was having a similar smoking issue when the O/X was on. I swapped out the O/X for the stock H pipe with cats, and the car doesn't smoke anymore. The cats definitely take care of the smoke.

 

[ripper]

Could also be sumthin stupid like your pvc valve. If its stuck you will smoke.

 

[WyoTechMSA]

After I put my O/R H on my car it did that for alittle while, especially if I ran the shit out of it. Have you tried Seafoam?

 

[Jrgunn5150]

It does it after running hard becuase it was dumping lots of fuel under load, then suddenly it isn't needed, so it goes a bit rich for a moment. Normally the cat's would catch it.

BTW, at best the active ingredient in Seafoam is Kerosene, but I put that crap in my engine and about 200 miles later I needed new o2 sensor's.

 

[ripper]

Run away from seafoam. Ive heard nuthin but bad stuff about it.

 

[WyoTechMSA]

Well Ive had nothing but good experiences with it so take it for what you will. Of course you need new 02s after using it, look at the shit that comes out of your exhaust after you use it, it has to clog the 02s, no way it wouldnt. ATF does basically the same thing.

 

[Jrgunn5150]

It's Kerosene, of course it smokes, look at the MSDS sheet on it.

 

[GREG@SN95]

If you have an OBDII mustang (96-04) and an offroad H... you need mil eliminators... they help correct the A/F ratio...

Black smokes means you are running rich...

Check your timing too...

 

[97$Cobra]

OK, I'll try replacing the pvc valve and I'll add some MIL-Eliminators and let you guy's know if it stopped smoking.

 

[97$Cobra]

Good info from Greg@95.......... I talked to a performance shop about the MIL-ELIMINATORS and he said the smoke I'm seeing is definately being caused by the air/fuel ratio going bonkers due to missing cat's. I ordered some up and hopefully everything will clear up (including the CEL L ight!) I will also be changeing out my pvc valve while I'm at it.

Thanks guy's.

 

[Magic]

Well Ive had nothing but good experiences with it so take it for what you will. Of course you need new 02s after using it, look at the shit that comes out of your exhaust after you use it, it has to clog the 02s, no way it wouldnt. ATF does basically the same thing.

How are you using the ATF? Method?

 

[GREG@SN95]

Good info from Greg@95.......... I talked to a performance shop about the MIL-ELIMINATORS and he said the smoke I'm seeing is definately being caused by the air/fuel ratio going bonkers due to missing cat's. I ordered some up and hopefully everything will clear up (including the CEL L ight!) I will also be changeing out my pvc valve while I'm at it.

Thanks guy's.

Yeah.... MIL Eliminators do more then turn off the Check Engine Light... Thats why they are important for OBDII cars without cats

 

[voidfinger]

Well Ive had nothing but good experiences with it so take it for what you will. Of course you need new 02s after using it, look at the shit that comes out of your exhaust after you use it, it has to clog the 02s, no way it wouldnt. ATF does basically the same thing.

Why not temporarily take your o2 sensors out? since when you crank the car up cold it runs for a couple mins with out reading the 02's... is this possible, about 10k or 15k ago i did it and i had to replace my drivers side upstream 02