I'm getting a downpipe from a member here soon and also a gutted high-flow cat. I don't want to get a CEL for a missing/inoperative cat so I'm thinking about doing something a lot of the 1.8T VW guys have been doing for years. It involves using spark plug non-foulers to space the O2 sensor out of the exhaust path and prevent the CEL.

Searched and searched all over the net, found some very interesting stuff, but most of it pertained to "tuning" the amount of oxygen the sensor sees, causing the ECU to recognize a "rich" condition and lean out the mixture and boost fuel economy. That's not what I want, obviously, but I understand a stock ECU makes the car run a bit richer than needed as a safeguard so it SHOULD be ok.

The car in question has been getting terrible gas mileage-- 13-15mpg, so I just replaced both the front & rear sensors a couple weeks ago. Mileage has gotten a lot better, hitting 20-22 in the city which I consider pretty good. I don't want to lose this and revert back to the terrible mileage I was seeing before just to avoid a CEL. Does anyone here know what the effect is on gas mileage by using a spacer like this to avoid a CEL? Theoretically, using some kind of O2 simulator does the same exact thing only with an voltage signal, so I'm interested in knowing the effect of such devices on mileage as well.

Well first off you're probably still running very rich from carbon buildup in the cylinders. I would start by Seafoaming the engine to get rid of that.

I haven't heard of any 2gnter's doing a spark spacer on the O2 but I understand the concept. in theory it should work, but I believe most people just use O2 eliminator kits.

Erik P.
Official 2GNT thread Hijacker
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Seafoam was already done, what a nice show for the neighbors

Got my new exhaust sitting here in the office waiting to go on. When I do it I will use a spacer and see what happens.

LMAO on the Seafoam show. It brings all the kids out in my neighborhood-and a few disgruntled old bitches.

I put the spacer on my rear o2 sensor about a year ago and the light stayed off for awhile. But the spacer gets dirty and i have to clean it every month it seems like. Next paycheck im getting the simulator so i dont have to worry about it. Let me know how it works out for you

I actually got hasty and just threw it all back together without the spacer, expecting to just deal with the CEL. Nope, no CEL here.. runs great and no light. I'll probably get it, eventually.