General Cat

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General Cat

NebulaStilo

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Hi guys

Bit of a back story.
Have performance and acceleration issues on my 1.6 Stilo. I have a Check engine light on. I have a elm 327 scan tool and put it on. It read O2 bank 1 sensor 2 heater malfunction.

So direct replacement. This month I planned to replace however we are too in lockdown and no spares shops open AS WELL as fact that I'm on a no work no pay.

While my stilo parked in driveway and not driving anywhere I noticed when pulling the car in and out of the garage,she has a random misfire. Spoke to some peeps and they said don't jump to O2 sensor just yet. Check that CAT may be blocked. I checked videos online and My symptoms are same as blocked CAT.

My question is,since my O2 sensor fault is post CAT,could it be that the blocked CAT is causing the O2 sensor to give in or give incorrect readings?
I removed it once and saw black residue on the sensor post CAT. Pre CAT was clear as day.

When revving i do get a clear white ish pale smoke coming from the exhaust with a fuel smell.

Thanks again!
 
Another thing,did anyone hollow out their CAT? If so,what did it do and does it harm the engine?
 
Not sure of the diagnostics on CATs and O2 sensors etc, far too technical for me, but I guess it'll never pass an omissions test on the MoT ever again if you were to do that.

.
 
Another thing,did anyone hollow out their CAT? If so,what did it do and does it harm the engine?

You are welcome to look how I did it on my post "
engine rebuild, Stilo Abarth 2.4 manual "

No, it does not harm the engine, other boxes will keep some back pressure.
 
Not sure of the diagnostics on CATs and O2 sensors etc, far too technical for me, but I guess it'll never pass an omissions test on the MoT ever again if you were to do that.

.
Here in South Africa I've never herd of them doing emmision tests though
 
You are welcome to look how I did it on my post "
engine rebuild, Stilo Abarth 2.4 manual "

No, it does not harm the engine, other boxes will keep some back pressure.

Thanks. Did it significantly change sound and power and will it solve my problem of having poor acceleration and power. She also doesn't rev up to red line. She gets up to 5000 and just sits there. Did it leave a fuel smell in the cabin?
 
It does make a performance difference, hence why I did it.
Sound, does change.

But I would first swop the Lambda sensors around and see if error code stay on same position.

For the engine not to rev past 5000 might be something else, a blocked cat would have to be really blocked for this.
Maybe remove pre Lamba sensor and see if revs go higher, thus in process can tell if it is the cat or not.
 
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It does make a performance difference, hence why I did it.
Sound, does change.

But I would first swop the Lambda sensors around and see if error code stay on same position.

For the engine not to rev past 5000 might be something else, a blocked cat would have to be really blocked for this.
Maybe remove pre Lamba sensor and see if revs go higher, thus in process can tell if it is the cat or not.

Thanks. I do have erratic idle and sometimes the car doesn't start on first crank. Moving through traffic can often be difficult because of revs. Higher revs she's okay but she just don't pull like she use to. Now and then on idles she misfires. Misfires only came during lockdown when she stood. Took her out for a spin and she misfired on pull away then came right and didn't come back. She pulled without misfire but a poor acceleration and hesitation. Unplugged MAP and car switched off so doubt its that.
 
I'm inclined to swap the lambda first, since a lambda issue is much more likely than a blocked cat'. If your car has 2 sensors then you can swap them over and see if the error message follows the sensor to its new location or whether it still gives the same error.

I only ever heard of a blocked cat' on diesels (unless you've tried running it on home-brewed fuel or something). If there is a blockage in the cat, then it could have occured because you have a duff lambda sensor, which may be causing the car to over-fuel.

The white vapour out of the exhaust sounds "normal" to a point... but are you losing coolant every so often? If you have a bleeding head gasket that might be disturbing the fuel-air mixture since coolant can be sucked into the chamber and water-glycol doesn't burn particularly well..

But start at "the most likely thing to go wrong" (it's "the most likely thing to go wrong" for a reason).. and that's the lambda sensor(s).


Ralf S.
 
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I'm inclined to swap the lambda first, since a lambda issue is much more likely than a blocked cat'. If your car has 2 sensors then you can swap them over and see if the error message follows the sensor to its new location or whether it still gives the same error.

I only ever heard of a blocked cat' on diesels (unless you've tried running it on home-brewed fuel or something). If there is a blockage in the cat, then it could have occured because you have a duff lambda sensor, which may be causing the car to over-fuel.

The white vapour out of the exhaust sounds "normal" to a point... but are you losing coolant every so often? If you have a bleeding head gasket that might be disturbing the fuel-air mixture since coolant can be sucked into the chamber and water-glycol doesn't burn particularly well..

But start at "the most likely thing to go wrong" (it's "the most likely thing to go wrong" for a reason).. and that's the lambda sensor(s).


Ralf S.

Hi Ralf. So,I checked now and saw that the CAT converter has already been removed by previous owner.

I swopped the plugs of the sensors around and it then returned bank 1 sensor 1 instead of sensor 2.
I am going to swop the actual sensors around and see.

The car has a slight misfire. Not enough to notice on idle but at higher revs it's enough to notice and then revs are also fluctuating.

Is it time for new sensor ? I removed it once before and it looked bit different to the pictures I see on the net. Looks black and damaged. It looks like the hot part of a old car cigerette lighter.

Thanks
 
I'm inclined to swap the lambda first, since a lambda issue is much more likely than a blocked cat'. If your car has 2 sensors then you can swap them over and see if the error message follows the sensor to its new location or whether it still gives the same error.

I only ever heard of a blocked cat' on diesels (unless you've tried running it on home-brewed fuel or something). If there is a blockage in the cat, then it could have occured because you have a duff lambda sensor, which may be causing the car to over-fuel.

The white vapour out of the exhaust sounds "normal" to a point... but are you losing coolant every so often? If you have a bleeding head gasket that might be disturbing the fuel-air mixture since coolant can be sucked into the chamber and water-glycol doesn't burn particularly well..

But start at "the most likely thing to go wrong" (it's "the most likely thing to go wrong" for a reason).. and that's the lambda sensor(s).


Ralf S.

Coolant level actually pretty stable. Hardly drops. Her temp stays at same point on guard when she gets hot.
She does have a poor fuel economy and seems its getting worse.
 
Poor fuel economy and a mis-fire is consistent with a dodgy lambda too (although just about any problem can cause poor economy and a mis-fire.. :D )

Lambda's usually show up around 3250 rpm, which is where the lambda heater switches off (since the exhaust gas keeps the sensor hot enough to work). If the sensor is sending abnormal signals because of a breakdown in the heater, then that will confuse the ECU.

Try accelerating slowly from 3000 to 3500 rpm, see if it hiccups around the 32-3300 rpm mark).

The lamda should look light-grey/tan (like a good spark plug). If it's sooty that might be because it's "cold" (and not cleaning itself) or something beyond its control is covering it with soot so it's getting drowned... but I'd say it's a dodgy lambda.


Ralf S.
 
Poor fuel economy and a mis-fire is consistent with a dodgy lambda too (although just about any problem can cause poor economy and a mis-fire.. :D )

Lambda's usually show up around 3250 rpm, which is where the lambda heater switches off (since the exhaust gas keeps the sensor hot enough to work). If the sensor is sending abnormal signals because of a breakdown in the heater, then that will confuse the ECU.

Try accelerating slowly from 3000 to 3500 rpm, see if it hiccups around the 32-3300 rpm mark).

The lamda should look light-grey/tan (like a good spark plug). If it's sooty that might be because it's "cold" (and not cleaning itself) or something beyond its control is covering it with soot so it's getting drowned... but I'd say it's a dodgy lambda.


Ralf S.

Ok so I tried. It hiccups on any rev and at idle. It's a continuous misfire. I changed plugs not long ago and all coil packs are working. I checked each plug and they all sparking. Sometimes there isn't misfire and theres times when there is. Like if I must pull into garage tonight then she will decide to not misfire then tommorow morning she might decide to work right.
She has a fluctuating idle right through. I changed plugs twice way before they were actually due. I changed them last around close to year end last year. Will coil packs give off a fault?
 
Poor fuel economy and a mis-fire is consistent with a dodgy lambda too (although just about any problem can cause poor economy and a mis-fire.. :D )

Lambda's usually show up around 3250 rpm, which is where the lambda heater switches off (since the exhaust gas keeps the sensor hot enough to work). If the sensor is sending abnormal signals because of a breakdown in the heater, then that will confuse the ECU.

Try accelerating slowly from 3000 to 3500 rpm, see if it hiccups around the 32-3300 rpm mark).

The lamda should look light-grey/tan (like a good spark plug). If it's sooty that might be because it's "cold" (and not cleaning itself) or something beyond its control is covering it with soot so it's getting drowned... but I'd say it's a dodgy lambda.


Ralf S.

it was covered in soot. Lots of it
 
I'm inclined to swap the lambda first, since a lambda issue is much more likely than a blocked cat'. If your car has 2 sensors then you can swap them over and see if the error message follows the sensor to its new location or whether it still gives the same error.

I only ever heard of a blocked cat' on diesels (unless you've tried running it on home-brewed fuel or something). If there is a blockage in the cat, then it could have occured because you have a duff lambda sensor, which may be causing the car to over-fuel.

The white vapour out of the exhaust sounds "normal" to a point... but are you losing coolant every so often? If you have a bleeding head gasket that might be disturbing the fuel-air mixture since coolant can be sucked into the chamber and water-glycol doesn't burn particularly well..

But start at "the most likely thing to go wrong" (it's "the most likely thing to go wrong" for a reason).. and that's the lambda sensor(s).


Ralf S.

Oh and for what it's worth Ralf,I occasionally get a MAP fault but after clearing it won't return with O2 bank 1 sensor 2. When unplugging MAP the car switched off. I cleaned it already
 
I'm inclined to swap the lambda first, since a lambda issue is much more likely than a blocked cat'. If your car has 2 sensors then you can swap them over and see if the error message follows the sensor to its new location or whether it still gives the same error.

I only ever heard of a blocked cat' on diesels (unless you've tried running it on home-brewed fuel or something). If there is a blockage in the cat, then it could have occured because you have a duff lambda sensor, which may be causing the car to over-fuel.

The white vapour out of the exhaust sounds "normal" to a point... but are you losing coolant every so often? If you have a bleeding head gasket that might be disturbing the fuel-air mixture since coolant can be sucked into the chamber and water-glycol doesn't burn particularly well..

But start at "the most likely thing to go wrong" (it's "the most likely thing to go wrong" for a reason).. and that's the lambda sensor(s).


Ralf S.

Hi Ralf.

I checked and it seems too that ive got a spacer on the post CAT sensor already too as you can see in the pic. Starting to think its the sensor thats gone bad. Going to try cleaning out the spacer and see what happens.
 

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That looks well placed to catch water and dirt. I think a cleanup will help.. particularly if the wiring connection to it is letting in moisture and upsetting the voltage - it doesn't take much to throw out the readings. If you're keeping any of the sensors, it may be worth sticking some silcone sealant at the joint.

Ralf S.
 
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