Help Please! Smell of unburnt fuel from exhaust, OBD II readings included in thread

[MLCMK]

Re-posted in the 350Z Technical forum

 

Hi all

 

Have a bit of a problem with my 53 Plate 350Z, 83,000 miles on the clock. Its fitted with a pop charger and Cobra exhaust from the Y pipe backwards. The car doesn't noticeably smoke at idle or high revs and seems to drive ok. A couple of weeks ago the orange check engine light was on so i did the pedal dance and managed to clear it first time, the car drove fine but last week but then the light came back on under high revs and didn't clear.

 

Over the past week I've noticed a slight smell of fuel when parked up on the drive so I bought a OBD II wifi plug and connected it up this evening after the car had been out for a 30 min run. At tick over while back on the drive, I got the readings below that I hope someone on here can make sense of :-)

 

S.T Fuel Trim B1 % = 3.9

L.T Fuel Trim B1 % = 3.1

S.T Fuel Trim B2 % = 1.6

L.T Fuel Trim B2 % = 3.1

Intake Air Temp degrees C = 62

Mass Air Flow g/s = 3.08

Throttle Position % = 0.4

O2S Location = O2S11

 

O2S B1,S1 V = 0.280

O2S B1, S1 STF % = 3.1

 

O2S B1,S2 V = 0.280

O2S B1, S2 STF % = 99.2

 

O2S B2,S1 V = 0.560

O2S B2, S1 STF % = 2.3

 

O2S B2,S2 V = 0.310

O2S B2, S2 STF % = 99.2

 

 

I'm guessing that the 99.2% values on both banks are indicative of an issue but I don't know where to start. Any advice greatly appreciated

 

 

Cheers

 

J

[Stutopia]

When you plugged in the OBD2 scanner, what was the code for the CEL?

[Richf]

Intake temps 62 degrees !

[Stutopia]

Intake temps 62 degrees !

 

Mine did that briefly, then went back to normal after a MAF clean.

[MLCMK]

When you plugged in the OBD2 scanner, what was the code for the CEL?

 

Unfortunately none were shown (I thought the pedal dance had cleared them?)

[MLCMK]

Intake temps 62 degrees !

 

Mine did that briefly, then went back to normal after a MAF clean.

 

Does this mean that I need to do a MAF clean then, I've read about that on this forum

[Richf]

If the ecu thinks the air temp is that hot it might run a bit poorly . Has to be worth a try

[MLCMK]

Thanks for your help both :-)

 

Here are some more data points I have just taken

 

1. At start up (literally just after the engine starts)

 

Coolant Temp degrees C = 13

S.T Fuel Trim B1 % = -10.2

L.T Fuel Trim B1 % = 6.2

S.T Fuel Trim B2 % = -10.2

L.T Fuel Trim B2 % = 7.0

Engine Speed RPM = 1262

Intake Air Temp degrees C = 14

Mass Air Flow g/s = 9.09

 

 

2. I then took the car out for a quick run (5 minutes) and sat at a bus stop and rev'd the car to approx 2,500 rpm and read the readings below

 

Coolant Temp degrees C = 82

S.T Fuel Trim B1 % = -3.2

L.T Fuel Trim B1 % = 7.0

S.T Fuel Trim B2 % = -0.8

L.T Fuel Trim B2 % = 8.6

Engine Speed RPM = 2550

Intake Air Temp degrees C = 16

Mass Air Flow g/s = 11.21

 

 

3. The readings below where then taken when I'm parked back on the drive with the engine ticking over

 

Coolant Temp degrees C = 88

S.T Fuel Trim B1 % = -5.5

L.T Fuel Trim B1 % = 3.1

S.T Fuel Trim B2 % = -6.3

L.T Fuel Trim B2 % = 3.1

Engine Speed RPM = 662

Intake Air Temp degrees C = 26

Mass Air Flow g/s = 3.00

 

 

The intake air temp seems very different from yesterday when the car had been driven for approx 30 minutes.........

Edited March 21, 2016 by MLCMK

[MLCMK]

 

To check the Mass Flow Sensor I just took the car out, pulled away from stationary in 2nd and accelerated until it hit the rev limiter. Graph of this is above.

 

 

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[MLCMK]

I also took another set of readings back on the driveway to see how the intake temperature looked, these are below

 

Coolant Temp Degrees C = 88

S.T Fuel Trim B1 % = -3.9

L.T Fuel Trim B1 % = 3.1

S.T Fuel Trim B2 % = -4.7

L.T Fuel Trim B2 % = 3.2

Engine Speed RPM = 650

Intake Temp degrees C = 50!!!!!!! (the sun is out in Milton Keynes but not to this extent ;-) )

Mass Air Flow g/s = 2.91

Throttle Position %= 0.4

 

O2S B1,S1 V = 0.285

O2S B1, S1 STF % = -3.9

 

O2S B1,S2 V = 0.520

O2S B1, S2 STF % = 99.2

 

O2S B2,S1 V = 0.560

O2S B2, S1 STF % = -4.7

 

O2S B2,S2 V = 0.70

O2S B2, S2 STF % = 99.2

 

So by the looks of things the first thing to investigate is the high reading on the Intake Temp but any other assistance would be great!

 

Thanks

 

J

[Stutopia]

The MAF is delicate, be careful removing and installing and clean using the appropriate process. I'm sure there's a guide on here. FWIW I don't think it will solve the smell of I burnt fuel but it won't hurt, if done correctly.

[MLCMK]

The MAF is delicate, be careful removing and installing and clean using the appropriate process. I'm sure there's a guide on here. FWIW I don't think it will solve the smell of I burnt fuel but it won't hurt, if done correctly.

 

Thank you SuperStu, I will search around for the guide and take a look at how tricky it is.

[Stutopia]

It's not difficult it's just delicate, my tech used a quick blast of electrical contact cleaner.

[MLCMK]

 

 

 

I just took a look at the sensor and to me it looks really clean so I'm not sure if it will need it (I was expecting to see something with dust and oil over it but it's shiny)

 

Can anyone who's seen a dirty one of the these comment?

 

 

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[MLCMK]

Just been out for a long run in the car, the intake temp rises when the car is stationary (I saw it go to 49 degrees at the McD's drive through) but as soon as I'm moving again it quickly dropped to 14 degrees C (7 degrees above the ambient temp at the moment) and stayed steady all the time I was driving so I don't think the MAF is the issue. Anyone got any ideas what I need to check next?

 

 

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[MLCMK]

 

Ran some cataclean through it today, no issues seen so I'll keep an eye on it and suspect some cats will be required at some point in the future

 

 

 

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[gillywig2]

When was the last time you cleaned/changed the air filter?

[MLCMK]

When was the last time you cleaned/changed the air filter?

 

I've had the car about 6 weeks so I don't know when it was cleaned before, do you think from the photo it needs a clean? I wasn't sure.....

 

 

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[monkeybrain1234]

When was the last time you cleaned/changed the air filter?

 

I've had the car about 6 weeks so I don't know when it was cleaned before, do you think from the photo it needs a clean? I wasn't sure.....

 

 

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I would give air filter a good clean, at least you can rule that out then.

[MLCMK]

When was the last time you cleaned/changed the air filter?

 

I've had the car about 6 weeks so I don't know when it was cleaned before, do you think from the photo it needs a clean? I wasn't sure.....

 

 

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I would give air filter a good clean, at least you can rule that out then.

 

You're right, it will be good to rule it out and to know what it looks like when clean, another job for the weekend then :-)

 

 

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[MLCMK]

Hi all

 

Just an update to this thread

 

Over the weekend I have done the following :

 

1. Cleaned and oiled the pop filter

2. Spark plugs removed (NGK Iridium) , cleaned and re-fitted (all plugs in good condition so no need to replace at the moment)

 

(great how to guide on the forum, http://www.350z-uk.com/topic/3690-how-to-spark-plug-change-vq35de/page__hl__sparkplug )

 

Car taken out for a drive to warm everything up

 

1. ECU reset performed

2. Accelerator Pedal Release Position

3. Throttle Valve closed Position

4. Idle Air Volume

 

Not convinced it's made much difference to the exhaust smell but the car definitely drives a bit better, more acceleration

 

Thanks for all on here who helped with advice etc

 

J

[davey_83]

How did you clean the plugs?

[MLCMK]

How did you clean the plugs?

 

They were pretty much clean when removed them but as they were out I gave them a gentle brush with a small wire brush (it's about the size of a toothbrush) to move any deposits on the tip then used some fuel injector cleaner to clean the end and remove any particles of dirt etc). Once they had dried I checked the gap and then put them back in the engine.

[davey_83]

That can scrap the iridium tips, you can wire brush copper ones but not iridium ideally

 

Cleaning the electrode with a metal brush can lead to electrode failure, look it up.

[MLCMK]

That can scrap the iridium tips, you can wire brush copper ones but not iridium ideally

 

Cleaning the electrode with a metal brush can lead to electrode failure, look it up.

 

Oops, old habit! Looks like I was lucky then not to damage them. Thanks for the advice, won't be doing that again 😀