Car stuttering...Bad MAF? Engine Misfiring, help! (Fault code P0300, P0301, P0302, and P0303)

[JoeyH]

Agree with the above.

Added to which you have both banks with a 32% long term fuel trim..

 

I have at present the same on one bank..the one with a static lambda reading.

It's not a coincidence.

I suspect that 32% is the maximum the ecu is able to adjust positive fuel trim.

That it's on both banks implies pre cat lambda issues on both banks. .

 

[DanMumford]

@JoeyH

On 8/24/2018 at 9:39 AM, JoeyH said:

regarding the lambda readings, we need to see a graph as although the voltages for both of the pre cat sensors are within range what I can't see is if they are oscilating as they should..

for all you can tell from that reading you could have one or both of the sensors failed just giving out a static voltage...

graph them at idle and post the results , but from the long term fuel trim I suspect you have at least one failing pre cat lambda, best to replace in pairs so you are in for 2 lambda sensors by the look of it..

 

Still haven't got round to fully sorting this out...been too busy...?

Anyway i've graphed the oxygen sensor readings now, I don't really understand what it means by "Bank 1 Sensor 1, Bank 2 Sensor 1" and "Bank 1 Sensor 2, Bank 2 Sensor 2"

Seems like readings for 4 sensors when I think there should only be 2??

 

 

[JoeyH]

Depending in year of boxster it's either 2 or 4..

Early  models have only precat sensors ..so just 2.

Later cars have 4, post and pre cat for each bank.

They should all be reading between .1 and one volt .

 

Around the 4 mark seems about right.

Look at them all separately just to see if one is acting up or tracking behind the others .

 

Your  precat sensors are the ones that have an effect on fueling so focus on those.

These are bank 1 sensor 1

And bank 2 sensor 1

Hope this helps.

[DanMumford]

It's a 1998 model so I would assume it only has the 2 precat sensors?

From the readings it seems like B1S1 and B2S1 are both reading less than they should so I'm guessing that would mean both sensors have failed?

Any idea what universal sensors are like?

 

Thanks!

[JoeyH]

I would fit only Bosch genuine..or at a push another respected OE supplier...recently fitted a Bremi MAF, a 3rd of the price of the Bosch item and its absolutely fine.

 

before you do that though, have a look to see if they have not wound themselves out, I had one that was barely finger tight ,which explained the 32%+ fuel trim on the corresponding bank I changed mine anyway as I was there...

 

you will find them behind the rear wheels screwed into to the top of the exhaust, one each side, post manifold and pre main cats..

 

regarding generic. well 02 sensors are a simple thing, but I couldn't be bothered faffing with the connectors so elected to save time rather than money and go with the OEM item.

also when chasing down faults like yours throwing in parts of unknown quality and or provenance can introduce another element of doubt when trying to diagnose issues in the event it doesn't fix the issue.

worse comes to worse buy 2 from ECP, fit them and see if it solves the problem, if not you have ruled out one of the likely culprits and can look elswhere and ECP are normally fine with taking parts back.#

for every 3 things I buy from them one goes back and I have never had a refusal.

 

best of luck.

 

 

[DanMumford]

So I purchased the correct tools needed to remove the oxygen sensors, jacked up the car and removed the wheel...but the b*st*rds are stuck solid, no amount of penetrating fluid + elbow grease can get them to shift at all, I'm pretty sure the metal of the sensors and the cats have fused together...

It also doesn't help that there's not even enough room to get the sensor socket plus the normal socket and ratchet in to place correctly...?

 

Looks like I'm going to have to take it to a specialist again and pay over the odds as usual.

[topradio]

Mine were like that. I cut the top off the sensor so I could get a long socket on it and then used a combination of heat on the pipe and freezer spray on the sensor and it came out with no signs of any threads left, it had fused together as you suggest. I then used a thread chaser to cut new threads in the pipe and was able to easily screw in the new sensors.