mr. Jones

problem: slow O2 sensor reponse with headers installed.
I had a good tune, street cam/head setup and long tube headers with high flow cats. I ran with the PO133, PO153 codes for a year and a half. New O2 sensors (Bosch 13111) did not fix it. My O2 heater circuit was working and fuse was never blown. Checked all relative ground connection (they looked great). No exhaust leaks.
I did not want to spend time revising the tune to fix this and I was due for the NJ inspection.
Heres what worked for me.
If you examine the bosch 13111 O2 sensor it has 3 very small slots in the protective cover over the sensor. These slots are how the exhaust reaches the sensor. Someone had reported better results with Denso O2's. I noticed that they had small holes in the cover instead of these small slots.
I drilled 6 small holes about 0.10 dia. in pairs, in the protective cover between the slots. See pics You must not drill to deep and damage the sensor. I used a drill press, set the stop on it and just broke thru the protective cover.
Installed the new modded sensors and all is good.
Cleared the computer, ran thru the GM computer ready requirements and I have not had a code or drivability issue since (approx. 500 miles to date).
I don't know how long the sensors will last. But I am good for two years or until I make a new major mod (or the sensor dies).
Give it a try

jimmyblue

iTrader: (11)

Good thinking, seems like this will let more heat in to fight
the heat losses through the body. Could you see any
changes to the switching waveforms after doing this?

mr. Jones

sorry but I don't have any scanning equipment.
It would have been nice to know the before and after.

I did also notice an improvement in cold engine characteristics
ex. below 150 deg coolant temp. I had some hunting for idle as the car came to a stop. When hot this was not there.

BigDaddyBry

iTrader: (15)

Funny, my problem is just the opposite, it hunts for idle upon hot start and when coming to a stop after a hot start. It usually dies.

Without a drill press what would you suggest?

jimmyblue

iTrader: (11)

A Dremel with cutoff discs could slot it finely, a
hacksaw or triangle file by hand. I'd go for the
power tool though, and plenty of shop air to get
rid of metallic residues.

gi8e7oi825

iTrader: (32)

Hmm... I like this idea! I will try it with a dremel & vacuum cleaner. If I screw up, I'll take the rear O2s to a local machine shop and run widebands in their place.

brad8266

iTrader: (23)

Good job Mr Jones Nice to see someone be innovative and fix a problem that lots of people here have.

mr. Jones

Yea the dremel tool should work. just be carful not to cut deep.

I had been following a post here on the bosch O2's with no solutions.
I figured all I had to loose was $80 for a sensor and a little time.

ShevrolayZ28

iTrader: (4)

I've read that with heated sensors the opposite is actually the case. In other words, with a heated sensor, more openings in the baffle allow heat to escape from the switching component within the sensor. It would actually stay warmer inside with less of an opening in the baffles. It makes sense, since with heated sensors the heat comes from within the sensor.

However, with non heated sensors, which rely on the exhaust to stay warm, opening the baffles will let more heat into the switching component.

Nevertheless, I will give it it a shot. This problem has been tormenting me ever since the LT's went in.

Thanks for sharing, Mr Jones!

ShevrolayZ28

iTrader: (4)

If this fixes the slow switching it may put credence to the theory that the problem is that the gases flow past too quickly to be sampled (Assuming that opening up the baffles allows more gas to get into the sensor.), rather than it being a lack-of-sufficient-heat issue.

mr. Jones

Please post your results.
can anyone post a scan of before and after sensor switching?
can anyone also verify the acuracy or change in air/fuel ratio with a modded sensor.
Thanks

ShevrolayZ28

iTrader: (4)

Sure thing, but it'll be a couple weeks before I get to it. I might just pry the baffle slits open and see if that helps.

JBIRD02

iTrader: (4)

What about the P1133 & P1153 (insufficient switching) codes? Will this work for those too?

jimmyblue

iTrader: (11)

The switching codes seem to be the first thing to
gripe.

With the heated sensor you have the potential for
heat loss to the gas, but I believe more significant
is the conduction loss to the header wall through
the sensor body. The gas heat has to overcome
this, it's evident that the heater power alone can't.
A higher flux of low-grade heat can make up for
the lesser temperature, from cooling, of the gas
if the problem is heat conduction away from the
element.

At least, that's the way I see it and the results
shown so far seem to bear it out.

98-LS1

iTrader: (4)

I wonder if this would cure a low voltage code that has me puzzled, I installed brand new Vette Bosch O2's but cannot get rid of this low voltage, bank 1 sensor 1. Think it's worth a try?

92SilverSHO

iTrader: (3)

good thread, ill be doing longtubes and since im lucky in life, i know my car will have this problems

red fury

iTrader: (1)

my car throughs the p1153 slow switch codes for both banks often during the winter....after reading this thread I went and compared the "factory" O2 sensor to the "auto-zone" bosch unit.....the factory unit has 8 slots compared to 3 on the autozone part, not to mention the housing/tip of the factory unit is much larger also! I plan on going back with the dealership on the O2's next go-around.

gi8e7oi825

iTrader: (32)

Well... I didn't use the dremel, I got lazy. I widened the existing holes a little bit with a small, flat screw driver. If I didn't have the screw driver I used, I'd probably have grabbed one found in those eye glasses repair kits. The picture below is of the B1S1 (modified) vs B1S2 (stock). Amazingly this has fixed my problem so far! I had every sensor code possible before. Now, after >1 hour idle tuning and 15 minutes of driving around, there's nothing, no codes.



I have plenty of before scans, but I'll get one or two tomorrow going to/coming from work (~35 mins). I'll also make sure that "my" version of this fix really did fix all my O2 problems. As you'll be able to see with the before scan (attached), B1S1 was always bouncing all over the place. It ALWAYS set my SES light first, and many times was the only reason the SES was light.

mr. Jones

the second start and run should confirm if it worked. No slow response codes for me since my mod. I have been out is some 40 deg. weather.

gi8e7oi825

iTrader: (32)

Well... I'm still getting the P0135 and P0155 codes, but they're not setting the SES. Normally the SES would have been set by now. Also got a P0140 but I couldn't care less about that.