Dorman 42009 Spark Plug Non-Foulers - 18mm Gasket Seat, 2 Pack

I used these to extend my number #2 O2 sensors because I was getting the catalytic converter inefficiency codes. You will need to drill them out so the O2 sensor will fit. I also painted them flat black so they were inconspicuous. I cleared codes and drove vehicle about 150 miles with no check engine lights. I then had it smog and have been driving it ever cents with no check engine lights. Much better than a $1200 catalytic converter!

Used this on a 2003 Toyota 4runner. I stacked them and drilled them out but could not get my sensor to thread in correctly as it would barely "catch" the thread. I drilled perfectly straight with new titanium bits but the sensor just didn't want to cooperate. The sensor was going in lopsided, indicating an error on my part. Ok, I can accept that. However, let's say I drilled perfectly straight, the sensor was too thick to get seated where it should be anyway so moot point. Anyway, after some time I was about to toss these things and call it a day. I ordered something else which I thought might work and figured while I wait the couple of days for delivery I would just slap this on since I had to drive my vehicle anyway. To my surprise, with not even a full turn of my sensor biting into the top adapter, my catalyst inefficiency code cleared after a few miles of freeway driving. I went to go smog immediately the next day and passed in...wait for it...California. Super happy but 4 stars for the grief of drilling through these things, they are tougher than one would imagine.

need to replace my catalytic converter on my Prius it kept popping up the code P0420 and I have these installed three days later my launch show that everything passed even though my evaporator system was good ! If you can prolong it to years I would say go ahead and do it the system that you can buy to replace your old Catayltic converter on your Prius is only $189 plus installation But for six dollars this is the sure bet!

So I did a thing. I bought a used, high mileage Prius to tool around with, and well, get 50mpg in the meantime. Lets me keep the miles off my truck. The guy I bought it from was super forthcoming about the Check Engine Light and the "oxygen sensor" that had "gone bad", but I knew better; at 212,000 miles and a known oil burner, the catalytic converter had become marginal, at best. After pricing out converters, on a Prius that I had only paid $2,000 for, I set out for alternatives. Found a great write up on using the Dorman 42009 non foulers on the downstream O2 sensor. Put them on the other day (drilled one of them out with a 1/2" drill bit), cleared the P0420 code, drove around reading live data and holy smokes!! It DOES work. My downstream O2 sensor was reading significant difference than my upstream, which indicates (read: tricks) my ECM into thinking it has a healthy working catalyst, and thus, no more check engine light!! VERY happy with the non-foulers.

Worked for my 2001 Audi A6 Avant!Like everyone else, these needed to be modified in order to fit the Bosch Oxygen Sensor. I used a ~15mm drill bit, and drilled down until it almost hit the bottom (see picture), and which point I installed these.After driving the car, and checking readiness, the catalyst readiness monitors passed!!My 242,000 Audi now has zero faults!

If you trying to de foul the oxygen sensor those they won’t work like plug and go ... the oxygen sensor won’t thread inside them because it’s long enough not to let the threads touch each other and they are way far ... so you will have to drill out (one of them )with 1/2 inch drill bit or maybe give it a little more and then stack the other one as is on the bottom ... so they will be like o2 sensor on top then the drilled one then the original one and attach it to the catalytic converter.You need to be aware of something ... they will be long all together so if you don’t have room to suggest to get an elbow shape.P.s: those spark plugs de fouler and you have to do this work .. if you wanna cut the time just buy the o2 de fouler it’s plug and go ... no need to drill anything.Hope this will help you guysUpdate: it didn’t solve the problem either ... I still have check engine light again

Works like it should be. Love that these comes with crush washers. It makes the purchase worth it. Not like others on here that doesn't comes wit washers. Bought these with the predrilled ones and connected one of these to one of the predrilled and installed it on a friends g35 sedan. Friend updated me... saying so far 100 miles driven and no more check engine light pops up. Vs before every 25 miles it used to cel up on dash. All in all glad products meets expectations. Will buy again in combo with predrilled ones. Only if they sells in packs of 4 (2 predrilled and 2 of these non-drilled defouler plugs).

In case someone else has this car, After downsrtream O2 sensor r/r the PO420 code STAYED GONE after clearing. Did the spark plug non fouler parts trick with a new sensor. Pretty sure the C/C was bad. The C/C replace was close to the cars value. Thanks to all the reviewers who helped me and my father save allot of money! We THANK you all so much!

As described, happy with my purchase

Definitely a 'must have' item for those wishing to pass their emissions test when it comes to completing the 'catalyst monitor'.This product will literally save you thousands.Consider the cost of replacing the catalytic converter (specifically the ones combined with the exhaust manifold such as the newer models Toyota Sienna).This product is installed downstream of the catalytic converter ' operating below threshold' after drilling a 1/2 " hole through it so as to accommodate the oxygen sensor..It will not affect the performance of the vehicle since it only monitors the performance of the catalytic converter (only the upstream oxygen sensor affects the fuel/air mixture ratio).It will not work with a 'plugged-up converter'.I have used this item several times and it has never failed me.

This is truly a no brainer. Couple of bucks to remove that pesky engine light AND pass e-test for my 05 BMW. Required some modification for Bosch 02 sensors, best to buy two per cat drill bottom one out completely hone out the other without losing the bottom hole on the second and use two if clearance allows keep small hole on the first one . Worked like a charm cleared codes and 300km so far no light . I will tell everyone I know who gets a cat efficiency code to get these. Thousands of dollars saved because of metal threaded spacers! Don't ever waste money on new cats. The government can kiss my butt or buy me new cats on their dime (technically my and your dimes) if it wants to. I'll buy these.

I needed a way to mount an O2 sensor for a gauge and this was a very economical way to do it.

These didn't fit my oxygen sensor and I tried drilling them out (which made them fall apart).They'd probably work fine on spark plugs.Just keep this in mind if you're buying it for oxygen sensors