P0174 appearance...

[Whisperhead]

Hello all, I hope you're well.

Today on my drive home, the MR-S lost some power at a few intervals. Felt like it was running on 2 cylinders, and sounded like a lawnmower.

It straightened itself out for the most part (the power came back) and although nearly stalled at some lights, I managed to nurse it home.

Sticking the code reader and Torque Pro on it, I found P0174 had popped up.

I've done some reading online, and here - I have a few points to check, such as swapping the O2 sensors around to see if the code follows (as my MR-S only has the two), and I'll be cleaning the MAF.

If I have no joy, can anyone suggest some other places to look? I'm crap at finding vacuum leaks, but the PCV valve I replaced a few months back with a new one, and the O2 sensor on the left side I replaced last year. Does P0174 correspond with that left-side sensor?

Some data that may help:

Idle RPM: 666-705RPM
LTFT1: -18%
LTFT2: 27.3%
STFT2: 19.5%
Throttle position at idle: 13.33%
Vacuum (idle): -25.18in/HG
Coolant: 96°

[Ardent]

@Whisperhead

Sent pm

[Whisperhead]

Thank you Ardent - that will be very helpful 

[Whisperhead]

Ok mini update - I decided to take the MR-S into a local garage for a diagnostic just for some peace of mind. They are telling me both O2 sensors need replacing. £150 each (1 is NGK, 1 is Bosch) plus their £80 diagnostic fee, making £380.

I know businesses need to make money, but this seems a little excessive to me. I'm gonna try metering the two sensors again, and see where to go from there.

[Joesson]

@Whisperhead

Hopefully you have not taken up your local garage's offer.
If you have, read no further.
If you have not, for rather less than the quoted price you can avail yourself of a diagnostic tool, various models are available, mine cost iirc less than £10 other members will advise as to the type they prefer.
Denso or NGK sensors can be obtained for around £75 each.
You will also need a sensor socked , comes with a split to allow the socket head to engage with the cable in place, around £10.
Very useful is a can or aerosol of Plus Gas to loosen the sensor, £9.99 from Screwfix and elsewhere.
In total less than half the price of your local garage, unless you rate your hourly labour very highly.

[Gaz mr-s]

Ok mini update - I decided to take the MR-S into a local garage for a diagnostic just for some peace of mind. They are telling me both O2 sensors need replacing. £150 each (1 is NGK, 1 is Bosch) plus their £80 diagnostic fee, making £380.

I know businesses need to make money, but this seems a little excessive to me. I'm gonna try metering the two sensors again, and see where to go from there.

FFS, that's robbery.

And I think they're wrong anyway.  MR-S  - so just 2 sensors.?   I was going to check cheapest sensors on ebay which I sometimes do for folk, but it probably isn't a sensor at all.

I've sent somebody a message who may be able to help.

In the meantime get yourself the Torque Pro app & an elm237 bluetooth OBD scanner.  £12 for the pair approx.

And before any other move bookmark this.   https://www.ebay.co.uk/itm/146529449077?_trksid=p4375194.c101949.m162918 

[Gaz mr-s]

I know businesses need to make money, but this seems a little excessive to me. I'm gonna try metering the two sensors again, and see where to go from there.

btw.....what do you mean by that?
Re-reading your 1st post mentions cleaning the maf, - can you confirm you sprayed up inside it, not the visible 'blob' ?

[Ardent]

Ok mini update - I decided to take the MR-S into a local garage for a diagnostic just for some peace of mind. They are telling me both O2 sensors need replacing. £150 each (1 is NGK, 1 is Bosch) plus their £80 diagnostic fee, making £380.

I know businesses need to make money, but this seems a little excessive to me. I'm gonna try metering the two sensors again, and see where to go from there.

Please tell me you have not gone ahead with their quote.
Sparkplugs.co.uk have always been competitive when I've needed to buy
Sometimes ebay or amazon. Depends on the day.
But cira 70-75 the last time I looked.
Stick with denso.
If you don't mind soldering crimping you can buy one with out the plug and transfer across. Too much phaff for me.

Edit
DOX0204. Just pumped into Google plenty sub 60.

And a plus 1 on the torque pro app and Bluetooth dongle.
Easy peasy on android. Historically apple phones seemed a bit picky in terms dongle and Bluetooth. Might not be true now.

[Carolyn]

I wrote a lengthy reply and then my internet crashed just as I was posting it...

Ah well:  PO174 is lean on bank 2, meaning on cylinders 2 and 3.  Bank 2 refers to just two cylinders, so the idea that you need two O2 sensors is just silly.

I would start by pulling the spark plugs and see what the electrodes looke like.  It only needs to be lean on one cylinder to show a 'bank2' code.  If one of the plugs is white, as opposed to light sandy colour, then that cylinder has a dodgy injector.  If two are white, then an O" sensor issue is the most likely.

My bet is on a dodgy injector - but yah never know until you investigate.

Don't be tempted to by a chinese injector -they are rubbish  I'd just source a known-good used green Denso injector .

If it's an O2 issue, these guys say theirs are 'Denso quality'.  They are unviersal fit and come with crimp connctors (denso wires don't like solder).  It's a simple job:

https://www.ebay.co.uk/itm/276896513070?fits=Car+Make%3AToyota%7CModel%3AMR2&_skw=O2++sensorToyota+MR2&epid=1532896001&itmmeta=01JT40059P0V9XVMG4DH693P12&hash=item4078517c2e:g:Yc4AAeSw3Ctnu~U4&itmprp=enc%3AAQAKAAAA0FkggFvd1GGDu0w3yXCmi1duqtAchX0nL28GMX1Sq4lmWiH1laTt62mMigGLBLPVuT15YSA%2BCNxrPMdLm8n792LerHFxph71sESx0xCEBCD5QSIkFpjjP6Ggph4QDTCzw8dZhvcOxgKWsp3VDnEGEJ%2BzETBIHXPr8Fsb6ZackzHucKzLlEGXLVZINMJf71h6cqEU9IYFmvsotbnr2Z%2BeuxVQR2twfPDoR04%2FpB7Xmh8bM7pT3GFJ%2FaNQ%2BvdrQphFhAT4qyl0JtczTjqmmAwi4sU%3D%7Ctkp%3ABk9SR9rXgIDRZQ

Stay far, far away from that garage.  They are incompetent thieves.

[Gaz mr-s]

If all 4 plugs look the same, I reckon the maf's likliest.

[SV-3]

Check the continuity at the sensors?

[Whisperhead]

Hello all,

Thank you for all your replies, helpful as ever. I didn't let them touch the car, just paid their diagnostic fee and took it back: I agree it seemed like absolute robbery. I did wonder why they thought both sensors needed to go if there was only a lean condition on one bank?

Just to address your questions:

@Gaz mr-s I meant that I'm gonna check there is continuity across the two like-coloured wires on each of the O2 sensors, to see if either is open circuit. I found my dead one last year this way (heater circuit had gone). I have Torque Pro and a handy little bluetooth OBD dongle, I agree it's super helpful. Carolyn helped me code it for japanese OBD.
Good spot on the MAF sensor, Ive bookmarked that page too, thanks for that one! My one did get a nice good dousing in electrical contact cleaner, including up into the housing, then let to air dry before refitting.

@Carolyn Thank you for this advice, Ill be pulling the plugs to check next chance I get to see how the electrodes look. Hopefully it's not an injector, as I don't know if I have the skill to swap one, and if I was going to, it would probably be prudent to swap all four. That might require a visit to a (different) garage to fit if it comes to that.

@Joesson Thank you for the clarification - £150 a sensor definitely sounded dodgy. Good shout on the PlusGas as well.


I will update again once Ive yoinked the plugs out and had a good look. I appreciate you all.

[Beachbum957]

This may seem obvious, but when was the air filter last changed? Verify nothing is in the airbox, like a mouse nest (been there)

Lots of good advice, particularly on the possibility of a bad injector or dirty injector.  If you buy an injector, avoid the cheap imports and try to get real Denso.  OEM would be either Denso, or some Aisin 

Typically, an O2 sensor failure will most likely be a heater circuit failure, which would give P0135 for bank 1.  Even then, any O2 failure should just put the system into open loop and not drop cylinders.

[Carolyn]

Hello all,

Thank you for all your replies, helpful as ever. I didn't let them touch the car, just paid their diagnostic fee and took it back: I agree it seemed like absolute robbery. I did wonder why they thought both sensors needed to go if there was only a lean condition on one bank?

Just to address your questions:

@Gaz mr-s I meant that I'm gonna check there is continuity across the two like-coloured wires on each of the O2 sensors, to see if either is open circuit. I found my dead one last year this way (heater circuit had gone). I have Torque Pro and a handy little bluetooth OBD dongle, I agree it's super helpful. Carolyn helped me code it for japanese OBD.
Good spot on the MAF sensor, Ive bookmarked that page too, thanks for that one! My one did get a nice good dousing in electrical contact cleaner, including up into the housing, then let to air dry before refitting.

@Carolyn Thank you for this advice, Ill be pulling the plugs to check next chance I get to see how the electrodes look. Hopefully it's not an injector, as I don't know if I have the skill to swap one, and if I was going to, it would probably be prudent to swap all four. That might require a visit to a (different) garage to fit if it comes to that.

@Joesson Thank you for the clarification - £150 a sensor definitely sounded dodgy. Good shout on the PlusGas as well.


I will update again once Ive yoinked the plugs out and had a good look. I appreciate you all.

Take the O ring off the MAf before you spray it.  Take care not to loose the screw - they're hard to relplace.

One bad injector doesn't mean you need to change all four.  I've got some spares and some fresh seals in my stash of bits.

[Gaz mr-s]

Hello all,
@Gaz mr-s I meant that I'm gonna check there is continuity across the two like-coloured wires on each of the O2 sensors, to see if either is open circuit.

Ok,  but a neater cct will give a different code & has no bearing on the engine running.

Did you tell the garage they were talking crap?  Pity it cost you £80.  Torque pro will tell you almost everything.

[Whisperhead]

I just went in and paid up, but I think they could tell I wasn't impressed with their diagnostic. They'd even ordered the two sensors from their motor factor in anticipation that I'd just tell them to go ahead.

Hopefully these pictures will show up. These are the plugs and MAF. Plugs are left to right, so 4, 3, 2, 1.

Since clearing the code, it hasn't yet re-emerged. Those plugs look a little dusty, and the third plug seems different to the rest (cleaner ceramic): any clues there?

[Carolyn]

please try again on the pics.

Cylinder #1 is to your right when looking at the engine.  (Just so we know we're on the same page )

How's it running now?

[Whisperhead]

I'm gonna take it for a drive a bit later so ill let you know how it is. Both sensor heater circuits are fine, just in case.

[Gaz mr-s]

Both sensor heater circuits are fine, just in case.

Now behave, you've been told, they work on cold starting to make the sensors work before exhaust heat.  The do nothing else.......

[Carolyn]

If anything, plug #4 looks slightly lean when compared to the others.  They do look like they've been in for some time.  Have you ever replaced them?

[Whisperhead]

Now behave, you've been told, they work on cold starting to make the sensors work before exhaust heat.  The do nothing else.......

Hehe - I couldn't resist! (The sensors could though apparently).

If anything, plug #4 looks slightly lean when compared to the others.  They do look like they've been in for some time.  Have you ever replaced them?

Those plugs are just about 12 months old now. I swapped them out last year in April/May when I bought the car, they're all NGK. The car has covered just over 10,000 miles in that time, as it's my daily driver. Worth a swap again maybe? The plugs are less than a fiver each to be fair.

The car drove better today on my commute, no bogging or power loss since the first incident. Ill scan again for a code later just in case there is anything pending in the ECU using Torque.
The idle is a bit more stable also, so I'll keep an eye on it over the next few days and update if anything else crops up.

Still getting that bloody oil spray under the engine lid every now and then though. Perhaps a new filler cap would help there, can I just change out the o-ring seal on it?

[Carolyn]

So - how is it running now?

[Whisperhead]

Sorry Carolyn - I edited the post above I think after your reply there - it's better for sure, so im gonna keep an eye on it over the next few days will update.

Thank you for all your help so far everyone!

[Carolyn]

Judging by the oil on the plug threads, I think you need a new cam cover gasket. That might deal with the oil spray. Don't go to Toyota for it, but also don't buy one of the cheap blue ones - they don't fit properly.

If you're not confident to do that job, bring it to me and you can do it with a bit of assistance.  I'm not far away.

A new ring in the filler cap would not go amiss.

[Whisperhead]

Sorry for the tardiness of the reply - it's been such a  busy month... Some updates!

First I checked my O2 sensors a week or two back, and lo and behold Bank 2 Sensor 1 was toast:
 


Replaced with a Denso one.

Having done some reading around the threads here, the cover gasket does seem like it might be the culprit as you say Carolyn, so I'll try to source one and see to that when I can - I appreciate the offer of guidance too, thank you.

Tracing down this oil leak/spray, I've given the engine a clean up and have added some UV dye to the oil, so over the next few days I'm going to be periodically looking over it for the source of the leak. Hopefully it'll make itself known.

Incidentally, while I was doing that, I looked under the oil filler cap:



I don't know if I'm just being blind here, but I can't see a seal on there? According to JapanPartsEU schematics, the seal is a removable part, so it looks like mine is missing? Or is it pressed into a seam?