Symptoms of bad O2 Sensor


2.2 Straight six
04-15-2007, 07:38 PM
My girlfriend has recently found that her truck shakes under acceleration. It was taken to a garage to be looked at and they said it had a bad sensor. (i'm assuming they meant O2 sensor) and they want $250 to replace it.

firstly, $250 to change any sensor takes the piss.

what are the symptoms of a bad 02 sensor? i just don't feel that a bad O2 sensor would make the truck shake under acceleration.

i know that the shaking could be caused by any number of things.

UncleBob
04-16-2007, 02:49 AM
*cough* what kind of truck is it (did I really need to ask you that?? :D )

There's a lot of sensors, I'd first want to know, are they really refering to the O2? And some O2's can be quite a pain to change out, but you didn't say whether that was just labor or parts and labor. Some O2's are over $500 for just the sensor (before labor)

As for the runnability issue: Depends on the vehicle. Some computers are more stupid than others, and will blindly adjust the fuel trim based on the O2 readings, and have no decent method for verifying the O2 is working properly. On those vehicles, they can definitely get the fuel trim so far off that it causes misfires.

CraigFL
04-16-2007, 06:34 AM
Another important key issue here is --- What codes are being shown? Is it the O2 sensor code? It doesn't ALWAYS mean a bad O2 sensor but it would sure point to at least testing it....

2.2 Straight six
04-16-2007, 07:33 AM
it's a 1997 Ford F-150 with the 4.6-litre V8.

She said all the she knew was that it was a sensor, but isn't sure which one. so i'm going to ask her mom (who took the truck to be looked at) if she knows.

i don't know what codes are shown, when i get there at the end of the week i'll get hold of an OBD II and find out. apparently the engine warning light's been on for two years...

i looked up Bosch sensors for this truck, they're no more than $40 each.

i know some are a pain to change, but i can do it myself without charging ~$200. i fixed the exhaust on my neighbour's Golf R32 yesterday, and to swap the O2 sensors on that you need to drop the front section of the exhaust. (that's not what we needed to do, but i could see how to do them)

UncleBob
04-16-2007, 11:33 AM
that computer is a smart one. It would sense a bad o2 in most situations.

the 4.6L likes to eat coils (COP) especially #3 cylinder

They also sometimes spit out the spark plugs, ripping the threads out with them.

find out the code, and I could offer more suggestions.

btw, list price for the stock part is $115, book time is .6hr. Here (at our labor rate) that would be pretty close to $200. They are not ripping anyone off, just charging what the going rate is

2.2 Straight six
04-16-2007, 12:01 PM
the stock part is $115? i found brand new Bosch ones for that truck for $40.

any ideas on what would cause the shaking on acceleration? i'd look more closely at engine/transmission mounts before sensors if my truck was shaking under acceleration.

what do i need to check the coils?

UncleBob
04-16-2007, 12:24 PM
the stock part is $115? i found brand new Bosch ones for that truck for $40.

any ideas on what would cause the shaking on acceleration? i'd look more closely at engine/transmission mounts before sensors if my truck was shaking under acceleration.

what do i need to check the coils?

misfires would definitely cause shaking. But until you get the code, I wouldn't make any big assumptions.

If the coil is completely dead, then simply test for spark. The fords are very oblivious to misfires sometimes....its SUPPOSED to set a code for it, but doesn't seem to most of the time.

If the coil is intermittant/partially dead, you'd need to scope it. Its also a good idea to pull all the coils and check for water/oxidization down the holes. Another common problem

The coils are a lot of fun to pull btw. We charge 3.2hrs, if I remember right, to do plugs. You let me know how quickly you get them done :D

2.2 Straight six
04-16-2007, 12:34 PM
i'll have to check for misfires and the like then.

i don't think i'll be doing anything too quickly. i spent 6 and a half hours under my neighbour's Golf R32 yesterday fixing his exhaust. stupid thing for our gates pulled his exahust system back by about 2".

i'll pull the plugs, check the coils and replace the plugs with new ones, and coils if they need to be replaced. general maintenance too.

how much would a new coil run me? (i wouldn't actually pay for it, it's not my truck)

also, in the US are there places you can rent jacks and axle stands? we have hire shops over here when you can rent that stuff out pretty cheap.

turtlecrxsi
04-17-2007, 01:16 PM
I believe Advance Auto rents tools out. I'm not sure about jacks and stands though. I know they rent out pickle forks for pulling apart CVs and engine hoists. Sears sells jack sets relatively cheap. I would think that a truck would be easily accessible from underneath. I know that I don't have to lift my Jeep at all when changing oil or accessing the undercarriage. Oh yeah, I'm sure you'll check the codes with a scanner. But one sure sign of a fouled O2 sensor is crappy gas mileage. Be sure to have fun while in the states...

2.2 Straight six
04-17-2007, 02:14 PM
i'm looking at jacks and stands are sear. ~$120 all in to lift and sit the truck. might just do that, have someone look after them and pick them up again when i move. besides, with the current exchange rate i can affors jacks and stands. (hurrah for me)

my girlfriend said her truck gets about 17mpg, and that sounds a little low for a 4.6 F-150. might just replace the sensors anyway. i think i'll give the truck a once-over. replace various parts to keep it on the road.

UncleBob
04-17-2007, 02:44 PM
no, thats pretty dang good actually

2.2 Straight six
04-17-2007, 04:11 PM
really?

that sucks by european standards. Our Golf V5 (2.3-litre) gets about 35mpg, and my mum's 4.2-litre XK (bear in mind it's a performance car) gets about 25mpg.

i'm starting to worry about the fuel costs of my truck (when i get it) because i want a 5.4-litre F-150 SuperCrew.

places like autozone do free fault code reading don't they? i don't feel like paying $99 for an OBD II scanner. especially when i've already set aside $400 for tools. (they're way cheaper over there.)

UncleBob
04-17-2007, 04:46 PM
the 4.2L sport car doesn't weigh 5000+ pounds though and have the aerodynamics of a brick :D

some autopart stores do read codes for free. Not on the receipt?

2.2 Straight six
04-17-2007, 05:53 PM
i don't have the receipt. my girlfriend's mom took the truck to be looked at. my girlfriend lives in Florida, and i live in London (UK) so i can't look at the truck until friday when i get there.

i'll talk to her mom and ask if she knows what sensor it is. i can't see a bad sensor causing shaking. of course, i'm assuming the sensor they were reffering to is an oxygen sensor, because it's not out of the ordinary for them to fail.

i'll take the truck to an autoparts store and have them read the codes. then get the truck up on jack stands and take a closer look and give it a once-over.

there's an advance auto about 8 miles from where i'm staying, so maybe they'll have an OBD II reader i can borrow, or they can use to read the codes. i'm expecting a misfire code more than an faulty O2 sensor code.

UncleBob
05-09-2007, 04:19 PM
so....you still wrestling with #7 & 8 plugs? :D

any resolution?

Moppie
05-09-2007, 05:40 PM
so....you still wrestling with #7 & 8 plugs? :D

any resolution?



He pulled all 4 plugs out, now he's trying to figure out why it still runs......

KiwiBacon
05-09-2007, 05:46 PM
As for the runnability issue: Depends on the vehicle. Some computers are more stupid than others, and will blindly adjust the fuel trim based on the O2 readings, and have no decent method for verifying the O2 is working properly. On those vehicles, they can definitely get the fuel trim so far off that it causes misfires.

A workmate did an engine swap in a Nissan ute. Put the 3.0 V6 in.
The auto electrician wired the O2 sensor in wrong, and the truck ran for about a month at 5:1.:uhoh:

It actually put out an orange cloud when revved off idle.

You guys do realise that UK gallons are bigger than US gallons (4.54 litres versus 3.6 litres)?

2.2 Straight six
05-09-2007, 05:50 PM
so....you still wrestling with #7 & 8 plugs? :D

any resolution?

she had it fixed before i got there.

and when i talk about measurements to americans, i work in US measurements.

moez1010@yahoo.com
08-12-2007, 09:20 AM
Yes Steven I agree it is not easy. Not like the real old days. Drop a littles gas in the carb. and see what happens. Now i guess it is the unplug it test. If things change then it probably aint it.

If a guy misses a couple days work messing around with it (-200) on a job that would have cost 175 then that person shouldnt be chaging a light bulb.

Unless; They just dont trust um. Like attorney's a few bad one's wreck it for all of um.

I can understand that and a person might say that the price is the reason vs I really dont trust you.

I fight the battles I can win. Wouldnt do a trans. Motor out. Not on your life.

Im learning the technical as I go along. On one engine on one car.
Some overlap from one car to the next and if I can pass something along great.

Steven in your estimation... What sensors whould be most sensitive to
heat? Should a car heat to almost overheating. O2 sensors being in the exaust would get pretty hot Perhaps one's in the block would be more prone to fail. What have you noticed over the 33 years in the biz?

I do know an electric fire (short) will cook all the thermal switches, idiot
lights, and coolant fan switches. (live and learn 86 Caravan)

If not heat alone. What about heat and then cooled quickly like perhaps
getting splashed from rain water or puddles.


Thanks Good luck

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