Oh, what a pickle! Stripped the threads in the downpipe of my 180k 95 Miata 1.8 M/T removing the old o2 sensor. Had a code 17 which to me fairly convincingly indicts the actual sensor. Looking for options. I have:
A HF flux wire welder and a Lincoln Tombstone that goes down to 40 amps and some small (5/64?) rod. I have welded exhaust before so I'm ok at not blowing through it. My welds usually turn out boogery and slightly porous.
A five pack of new pre-threaded mild steel sensor bung holes. 18x1.5mm, 0.400" thick.
A new, possibly counterfeit, Denso universal 4-wire o2 sensor.
The problems:
-- The downpipe is only available from Mazda, for $270. There is no aftermarket part. There's a 30 year old used one on ebay for $150.
-- I ran a thread chaser down the hole, potentially crooked, as I hadn't evacuated all the stranded threads. Access isn't great.
My options, as I see them:
-- Buy the new pipe. The threads on the header and cat don't look too awful, though access isn't great, and of course it's opening a can of worms. Save this for last.
-- Thread the thread chaser through the new bung into the old one so they meet up square. Pre-bevel the new one so there's a vee for the weld to fit in. Weld. Con: Sensor won't stick as far into the exhaust stream, will react slower. Pro: Best workmanship with limited skills and space. I could do this, then if it doesn't work well, move on to another plan.
-- Put a plug in the existing hole, grind a concave curve in the new bung, weld to the pipe about 2 inches from the existing hole. Pro-- Sensor will stick well into the pipe. Con-- weld needs to be perfect as an air leak here will throw off the fuel mix.
-- Gingerly put the o2 sensor in the existing hole, and tack weld it so it won't fall out. Pro-- Cheap. Con-- Sensor might not last very long, being purchased on an internet auction site of dubious distinction.
What say y'all?
A HF flux wire welder and a Lincoln Tombstone that goes down to 40 amps and some small (5/64?) rod. I have welded exhaust before so I'm ok at not blowing through it. My welds usually turn out boogery and slightly porous.
A five pack of new pre-threaded mild steel sensor bung holes. 18x1.5mm, 0.400" thick.
A new, possibly counterfeit, Denso universal 4-wire o2 sensor.
The problems:
-- The downpipe is only available from Mazda, for $270. There is no aftermarket part. There's a 30 year old used one on ebay for $150.
-- I ran a thread chaser down the hole, potentially crooked, as I hadn't evacuated all the stranded threads. Access isn't great.
My options, as I see them:
-- Buy the new pipe. The threads on the header and cat don't look too awful, though access isn't great, and of course it's opening a can of worms. Save this for last.
-- Thread the thread chaser through the new bung into the old one so they meet up square. Pre-bevel the new one so there's a vee for the weld to fit in. Weld. Con: Sensor won't stick as far into the exhaust stream, will react slower. Pro: Best workmanship with limited skills and space. I could do this, then if it doesn't work well, move on to another plan.
-- Put a plug in the existing hole, grind a concave curve in the new bung, weld to the pipe about 2 inches from the existing hole. Pro-- Sensor will stick well into the pipe. Con-- weld needs to be perfect as an air leak here will throw off the fuel mix.
-- Gingerly put the o2 sensor in the existing hole, and tack weld it so it won't fall out. Pro-- Cheap. Con-- Sensor might not last very long, being purchased on an internet auction site of dubious distinction.
What say y'all?
