O2 Sensors and MPG. Cleaning O2 sensor

[Roadtripp]

Does a faulty O2 sensor reduce fuel mileage? So the idiot light, check engine, light comes on and then goes away. I had the codes read and got a O2 sensor code. It’s a 2002 Chevy Express. 305 vortec engine. It has a lot of power and crummy fuel mileage. Around 10 mpg. When I cleaned out the intake manifold last Fall it was gunked up with carbon. It seems to have more power now than before. Has anyone tried cleaning a O2 sensor? Thanks

[B and C]

O2 sensors can cause a rich mixture which will kill gas mileage. I have never tried to clean one, I always replaced even though they can be spendy.

[sternwake]

They are known to get lazy, but not set computer codes.


I replaced more than one when it just smelled rich and mpgs were less than expected.  Usually mangle mine with vice grips to to get them out, even with the pre installed antiseize.  The 02 sensor sockets I had access to, were too thick to fit.

Find out which outfit originally provided the 02 sensor for  your chevy.
  Bosch 02 sensors and Dodges are not happy with each other, need to use NTK or denso, not sure if Chevy are as finicky.

I killed one 02 sensor when my fuel pump failed in an intersection in Baja, and i drove it out of there spraying throttle body cleaner down the throttle body.  Never got any OBD1 codes for 02 sensor voltage out of range or running rich or lean.

No experience with cleaning one.

[Roadtripp]

Ok, thanks. Wow, how much throttle body cleaner did that take to drive the van ?.
I can’t ignore it much longer. The exhaust smell getting richer. I read it can contribute to clogging or burning out the catalytic.
The AC Delco website says it is essentially metering the exhaust gas and the outside air and feeding that data to the computer to keep the air fuel at ratio. It says it is the “primary device” . Since it’s a PITA to replace in this farm mud pit I’ll install new sensor rather than try cleaning:

“Is there a problem when my “Check Engine” light turns on?
Yes, it could be due to a contaminated sensor probe, broken sensor body, internal sensor failure or external electrical failure.”

“Can ACDelco Oxygen (O2) Sensors help maximize the gas mileage for my vehicle?
Yes, ACDelco Oxygen (O2) Sensors are the primary devices on your vehicle that measure the proportion of oxygen in emission and gases with the amount in outside air. Using this measurement, the vehicle computer can adjust the air/fuel ratio to the optimum value of 14.7:1. At this ratio, engine performance, emissions and fuel economy are optimized.”

[Blacktank]

yes they can,the o2 censor reads the exhaust gasses and changes the fuel mixture for optimal running

i have heard of people cleaning them,they are sensitive to chemicals,never done it,i get new ones
https://www.rockauto.com/en/catalog/chev...ensor,5132
the code should of told you which one was bad

a plugged air filter can choke the engine setting off o2 codes

a can of fuel injector cleaner every month or three will keep things clean and the injectors spraying correctly

[Blacktank]

no posting the answers right before i post the answers

[sternwake]

Ok, thanks. Wow, how much throttle body cleaner did that take to drive the van ?. 

It was 2006, I can't really recall exactly, I needed to get about 35 yards to the side of the road and out of the way.
I'll guess a quarter can for that and a quarter more for diagnosing and relocating once i was towed to a local farmer's properly to drop the tank and replace the fuel pump.
The can did say 02 sensor safe though.  NO doubt I just blasted tons of carbon from valves and piston tops past the sensor driving it on the cleaner.  The product itself might be OK for the sensor, but not what it removes, not all at once.

[Roadtripp]

yes they can,the o2 censor reads the exhaust gasses and changes the fuel mixture for optimal running

i have heard of people cleaning them,they are sensitive to chemicals,never done it,i get new ones
https://www.rockauto.com/en/catalog/chev...ensor,5132
the code should of told you which one was bad

a plugged air filter can choke the engine setting off o2 codes

a can of fuel injector cleaner every month or three will keep things clean and the injectors spraying correctly

Ok, thanks,  what a relief, only ~$29 for AC Delco O2 sensor. I thought they go for $100’s. Am I correct to ASSume with my stock exhaust and emissions V-8 engine there are 2 upstream and 1 downstream sensor? And ordering the tool and the same time makes sense. 
 Yes, the air cleaner is 6 months old and I’ve tried the Sea Foam stuff people rave about so much.

[Roadtripp]

Ok, thanks. Wow, how much throttle body cleaner did that take to drive the van ?. 

It was 2006, I can't really recall exactly, I needed to get about 35 yards to the side of the road and out of the way.
I'll guess a quarter can for that and a quarter more for diagnosing and relocating once i was towed to a local farmer's properly to drop the tank and replace the fuel pump.
The can did say 02 sensor safe though.  NO doubt I just blasted tons of carbon from valves and piston tops past the sensor driving it on the cleaner.  The product itself might be OK for the sensor, but not what it removes, not all at once.

Ok, thanks. Sounds like a adventure and spur of the moment improvisation. That brings up a entire other subject and possible thread. I abhor the notion of dropping the tank and a internal fuel pump. Maybe it’s not that bad on a van and I fret too much. I miss my old cars with a inline or engine mounted fuel pump. Has anyone heard of a inline fuel pump that works with fuel injection? It’s another case where I’d like to get the engineers who put the fuel pump in the tank to repair it. I’ll search to see if a thread already exists for this.

[sternwake]

Whether an inline fuel pump can suck fuel past a failed in tank fuel pump is likely vehicle / pump specific.

I've done the seafoam thing too a good decade ago. A lot of the Smoke out the exhaust, is simply the 40% by volume pale oil, being burnt, rather than the carbon build up in the engine being burnt off/ cleaned. I do believe that these quick and dirty chemical combustion cleaners do help push old 02 sensors past their usefullness. The seafoam thing did seem to improve idle smoothness. I can't say it is ineffective, just that the smoke cloud is not indicative of a carboned up engine being spotlessly clean internally afterwards.

If one is going to replace the O2 sensor, then doing the seafoam, or water decarbonization, or even the intank fuel system cleaners is called for, right before replacing the 02 sensor. Might want to hit its exterior with some penetreating oil for a few heat cycles before hand too. Few come out easily without lots of torque and cursing.

Also note that fuel system cleaners can show up on used oil analysis, so many say to add them just before an oil change so as to not negatively influence the cleaning or lubricating properties of the engine oil.

A very effective decarbonization can be done by allowing a distilled water mist be sucked into the running engine. One must be careful not to hydrolock it though. If you've ever seen a cylinder twhose head gasket was allowing coolant to enter the combustion chamber, you will see it is practically devoid of carbon on piston top and valves.

As far as fuel system cleaners one puts in teh tank, those with Poly Ether Amine, PEA, are said to be most effective and safe. They clean without leaving any Deposits of their own. not all Fuel system cleaners use PEA, seafoam does not.

Gumout Regane does, Redline SL-1, CRC Guaranteed to pass, and several others Do. Techron was the original PEA fuel system cleaner and all top tier fuels use a small amount of this cleaner in them. but reports of techron lately, at least some formulations of it are said to be quite low on PEA. I use the Gumout regane high mileage as it is easily available for 5$( treating upto 17 gallons) at wal mart. PEA has a distinctively Fishy odor. Gumout products that do not say Regane on them do not have PEA.

As far as replacing the in tank fuel pump, some make access hatches above the tank so the tank need not be dropped. Safest to do when the tank is already out of course, and there is no guaranbtee a hatch can be placed where needed in any given vehicle.

As far as your chevy having 2 02 sensors upstreeam and one downstream of the Catcon, I dont really know. The one after the cat does not affect A/F mixture, it only tells whether the catcon is still functioning properly.

My '89 Dodge is OBD1 and has only one 02 sensor on driver's side exhaust manifold, accessible through the wheel well.



I thought i was having potential fuel pump failure warning signs 6 or 7 months ago with random stalling with low fuel levels, but have driven close to 7k miles since without issue. Not sure what it was, and whether the few things i eliminated as potential culprits were indeed the culprits.

Dropping the tank is not fun, especially when it has over 20 gallons of fuel left in it. Hardest thing on my van was a deep enough 5/8" socket to reach the nut on the J bolts, and the fact that there was 4 inches of rusted threads to deal with.

Did you ever get that papst 283cfm fan and test its amp draw?