daltvater

Need a little help here. I removed the cats and now the car is running really really rich. So bad that my wife is getting sick of the couch smelling like fuel.

My question is how do I fix this and was it running rich before the Cat-Bypasses? I’m debating on if I should put the Cats back on or should the chip be remapped? Pretty sure it an aftermarket chip, I’m going to dig through my stuff tonight to see what kind of paper work I have on the chip.

Car is a 95' with Maxflo mufflers and a Fabspeed Bypasses.

thanks!

herman maire

Probably the 02 sensor is damaged.... Your sure you reconnected the o2 ? I gutted my cat and it does not run rich at all.

JDHertz11

I had the Fabspeeds with a chip and the car still smelled rich, but not as bad as yours sounds to be. I recently sold the car, but I still have the chip. Would you like to try it to see if it helps your problem? It is from a 1995 6 speed 2WD. The car was noticeably quicker as well (maybe it made 12HP...)

NP993

How do you know that it is running rich?

Obviously, the exhaust is going to smell different once the cats are gone. That's perfectly normal. Have you actually tested the exhaust with a CO sniffer or an LM-1?

daltvater

I reconnected it. Maybe I broke it at the time? I did twist the wires up getting it off.

daltvater

I am getting heavy backfires on upshifts and deceleration. Maybe it's not running rich. I've ran a bypass on my last Porsche but the strong smell of unburned gas wasn't there before.

daltvater

Thanks JD, I may take you up on that. Thanks for the offer, I'm new to this site but I'm loving it already.

Wilder

Welcome to the wonderful world of cat bypasses. There is nothing wrong with your 02 sensor. It'll run rich (as defined by poor fuel consumption) and smell like gas and you and your wife will either get used to it or not. It made my fiancé sick and she wouldn't get in the car after a while. A chip won't help either. I have Rennsport.

Bypasses sound awesome and there's a thread kicking around with dyno numbers showing ~12HP increases IIRC but you may want to consider sport cats for a DD and wife hauler...catbypasses belong in track cars IMO.

JDHertz11

Just PM me your shipping address (FedEx deliverable) and I'll send it to you to try. It seemed to make the car feel smoother and more responsive, but that usually happens when things cost you money....

Black993

the big question is how does it sound!

NP993

I've got bypasses on my car and don't have any of these symptoms, not does the car smell like gasoline, nor has fuel consumption worsened, as Louis claims below (in fact I've never heard of cat bypasses affecting fuel consumption).

The way to tell for sure if you're running rich is to hook up an LM-1 or have the CO checked at idle by a shop with a sniffer. Neither of these is hard to do. And keep in mind that installing the bypasses might not be the culprit here -- cats do a good job of concealing engine problems, like high oil consumption, and the odors caused by a rich condition. Your problem might have preexisted the bypasses.

Wilder

Noah, prior to install of my cat bypass, fuel consumption was normal...~18MPG city. Directly after install, consumption dropped to ~11MPG. I recall searching here and finding posts that confirmed this to be normal. The same search confirmed that gas smells are also normal, in fact, the seller warned me about the issue prior to my purchase. I got used to it and didn't notice it much after a while but my fiancé could never get used to it. After I took them off, consumption went up agin to within normal range.

Bill Verburg

My guess is that the O sensor is not functioning correctly. W/o a functioning O sensor the engine does go into a rich, open loop, limp home mode. The connecting wire is the ingress route for the comparison sample air necessary to proper O sensor function(the O sensor develops it's control current from the difference in O content between the exhaust gas and sample air)

As an aside, a cat does clean the air, those of us that are old enough remember when all exhaust smelled like that. However there is also a spectrum, almost clean from a newish tight engine to the rank aroma from an older loose engine. The odor is a combination of burned and unburned oil, and cumbustion byproducts. Neither of my 993 engines has a cat. The new tight 3.8 is fine, the older, loose 3.6 is noxious, even to me, though i've owned worse.

Wilder

Bill, when I was running my bypasses, I was running them with RSRs. I also notice that the OP has Maxflows. Wouldn't the higher-flow mufflers make the odor even more evident?

daltvater, also in regards to the "backfires", do you mean more bite and burble perhaps? It's normal for cat bypasses to burble and pop on decel.

Bill Verburg

I don't believe so, I go back and forth between stock mufflers and RSRs a lot. The only difference I notice is noise