Oxygen sensor readings

[TominMO]

95 Aspire. OBD-I.

On this last tank of gas, my mileage dropped significantly. I have recently done a complete tuneup--air filter, NGK plugs and wires, good quality cap and rotor. Car runs great, but mileage has dropped. At the same time I filled up and noticed the mileage drop, I also stuck a bottle of Sea Foam in the gas BTW.

I'm thinking the O2 sensor. So I checked the voltage readings with my digital multimeter, and it read as expected--up to a point. When I started it cold, the reading was below .1v and gradually climbed as the motor got hotter. The max it read was .68v, but the Haynes manual sez the range should be from .1v - .9v.

So is my O2 sensor going out? Has anyone confirmed with a new sensor when they installed it that the proper range is indeed .1 - .9v?

[eurotiva]

Festiva, or aspire?

[TominMO]

Aspire. Sorry, I edited when I realized that I had not specified the car originally. BTW Rock Auto shows the same O2 sensor for all EFI Festys and all Aspires, whether OBD-I or OBD-II. (Of course the 96-97 OBD-II Aspires also have the other O2 sensor ahead of the cat.)

[boydg1]

.... You may want to consider reading "POST #6, #7 and #9" of this thread, especially, in helping to resolve your problem: http://www.fordfestiva.com/forums/sh...ad.php?t=33945

.

95 Aspire. OBD-I.

On this last tank of gas, my mileage dropped significantly. I have recently done a complete tuneup--air filter, NGK plugs and wires, good quality cap and rotor. Car runs great, but mileage has dropped. At the same time I filled up and noticed the mileage drop, I also stuck a bottle of Sea Foam in the gas BTW.

I'm thinking the O2 sensor. So I checked the voltage readings with my digital multimeter, and it read as expected--up to a point. When I started it cold, the reading was below .1v and gradually climbed as the motor got hotter. The max it read was .68v, but the Haynes manual sez the range should be from .1v - .9v.

So is my O2 sensor going out? Has anyone confirmed with a new sensor when they installed it that the proper range is indeed .1 - .9v?

[TominMO]

.... You may want to consider reading "POST #6, #7 and #9" of this thread, especially, in helping to resolve your problem: http://www.fordfestiva.com/forums/sh...ad.php?t=33945
.

Thanks boyd. When I did a search earlier I saw that thread, but there were five pages of threads and according to the title, it was about physically replacing the sensor, do I didn't dig down into it. Good info there.

Festyboy's remarks also tell me that I have a Bosch in my turbo B6 Festy. Out of curiosity I went out and checked it with the multimeter. I'll change that too.

[FestYboy]

tom, are you using a Fluke meter or somthing cheap? if it's a cheap one, it can't react fast enough to show you what the o2 is doing, and if it's like most meters, it's taking an averaged reading. also, the o2 may be slow to react at idle, try reading at 1500rpm where there's enough heat in the exhaust to keep the o2 active.

[ericsmith32]

Aspire. Sorry, I edited when I realized that I had not specified the car originally. BTW Rock Auto shows the same O2 sensor for all EFI Festys and all Aspires, whether OBD-I or OBD-II. (Of course the 96-97 OBD-II Aspires also have the other O2 sensor ahead of the cat.)

Yeah Tom they're the same which is nice! I ordered a o2 sensor originally for one of dad's Festiva but used it on the Aspire instead. Got it from here... http://www.oxygensensor123.com/ShopB...ASPIRE&mode=EG ..$13.75 free shipping. Tom was this just over one tank? Bad gas.. and no not the type I have.

[TominMO]

tom, are you using a Fluke meter or somthing cheap? if it's a cheap one, it can't react fast enough to show you what the o2 is doing, and if it's like most meters, it's taking an averaged reading. also, the o2 may be slow to react at idle, try reading at 1500rpm where there's enough heat in the exhaust to keep the o2 active.

Brand name is Micronta, from Radio Shack. Had it a long time. It did perform as I expected, i.e. the reading went up gradually as the motor heated up, from just over .0 to .68. I'll try it at 1500 rpm tomorrow.

Yeah Tom they're the same which is nice! I ordered a o2 sensor originally for one of dad's Festiva but used it on the Aspire instead. Got it from here... http://www.oxygensensor123.com/ShopByVehicle.epc?q=1995-FORD&yearid=1995%40%401995&makeid=28%40%40FORD%40% 40&yearid=1995%40%401995&makeid=28%40%40FORD%40%40 &modelid=6831@@ASPIRE&mode=EG ..$13.75 free shipping. Tom was this just over one tank? Bad gas.. and no not the type I have.

RockAuto lists the '95 Aspire Denso O2 sensor as part #2341020, the Festy, Escort GT and gen2 323 as #2341010.

Sorry to hear about the bad gas.

[ericsmith32]

I believe those part #'s are the ones you don't have to re-wire. All the 2341000 series is the same except the wiring harness. What's to be sorry about bad gas? I quite enjoy it!

[TominMO]

tom, are you using a Fluke meter or somthing cheap? if it's a cheap one, it can't react fast enough to show you what the o2 is doing, and if it's like most meters, it's taking an averaged reading. also, the o2 may be slow to react at idle, try reading at 1500rpm where there's enough heat in the exhaust to keep the o2 active.

Went out and re-tested the O2 sensor. At a fast idle (1500) it behaved normally, i.e. going from .00 - .68 volts as before. When I revved it to 2000, the readings did get up to .89, then started going all over the place. I'm just gonna replace it with a new splice-in Denso universal (#234-1000, about $20). Same for the Festy, which seems to have something other than the Denso.

[FestYboy]

actually, it's SUPPOSED to go all over the place. that's the point... and also why i asked what meter you were using. An o2 is supposed to swing from rich to lean several times a second and most meters can't read that fast. Also they need to be up to temp to read properly (ie over 600*) and the ECU won't look at them till they are up to temp before going into closed loop, that's why new cars have heater circuits in them for the o2 to shorten the time to get to closed loop.

[TominMO]

actually, it's SUPPOSED to go all over the place. that's the point... and also why i asked what meter you were using. An o2 is supposed to swing from rich to lean several times a second and most meters can't read that fast. Also they need to be up to temp to read properly (ie over 600*) and the ECU won't look at them till they are up to temp before going into closed loop, that's why new cars have heater circuits in them for the o2 to shorten the time to get to closed loop.

OK, good info, thanks. Guess mine's working then. Still gonna replace the Festy one, which reads .85 from the get-go (gen 2 B6 in the Festy, but uses the same one). When I pull it I'll let you know the brand, if possible.