CEL Light after...

[weddallenko]

Hi Guys,

I've looked through some posts on what could cause my CEL light to come on...it's only come on after some 'tinkering' this morning   s:oops: :oops: s:oops:  
No code reader to determine the cause...
I replaced the stock manifold with a 'performance' de-cat type and cleaned the MAF sensor a few weeks back, the manifold was a complete nightmare to change!

Anyway, whilst waiting for the group buy on markiii pipes I decided to attempt  a bit of DIY this morning http://www.mr2roc.org/phpBB3/viewtopic.php?f=7&t=31417&hilit=diy+inlet along the lines of this..
It's after this that the light has illuminated, have I fubarred something?
Is there is a 3rd o2 connector in the area by the air intake that I may have damaged?
Is my MR-S gonna do an Airbus A380 on the way to Sainsbury's??  s:cry: :cry: s:cry:  

Many thanks in advance...

[Mad Matt]

I didn't think the MR-S had the third O2 sensor. On my MR2 the third sensor plugs in behind the rear light which you probably took off to play with the intake so check it's not been knocked out (if you've got one).

The best advice though is to get the code read. There's a list of members with readers so you might find someone near you, or you can buy one for a few quid.

[Anonymous]

 l viewtopic.php?f=47&t=31275&p=381395&hilit=paper+clip#p381395 l

[nathanMR2]

whats about you from? U really need the code read.

You could have damaged one of the sennors on removal.

[weddallenko]

Cheers guys,

I'll have a look for a paperclip and see what code comes up...
It seems strange that it could be the O2 sensors, its about 3 weeks since they were removed and the new manifold fitted.
Like I said, this happened literally about 5 mins down the road after fitting a larger diameter intake pipe to the filter box, is the car throwing it's toys out the pram cos it don't like the greater volume of air its getting?
I did reset the ecu for about 45mins and the light didn't come on until 20 minutes of driving, I guess this is irrelevant though as it's in some kind of learn mode??
Now it seems to be on as soon as the car starts...  s:cry: :cry: s:cry:  
Is it safe to drive now... my mrs has a Fiat Seicento, there is no freaking way I want to be borrowing that!    s:wink: :wink: s:wink:    s:wink: :wink: s:wink:  

Thanks in advance again...

[roger]

For quite a few codes you have to have 2 failures, that's why sometimes it takes a bit of time foe CEL to come back.

[weddallenko]

Hi,

Well, I start the car and the cel light is on straight away. Turn it off and use the paperclip, turn the ignition to on and no cel light or any flashes...
ABS light flashes but no life from the cel light...  s:? :? s:?  

Any ideas guys?

[frogger]

Sounds like you've already gone after the likely problems (MAF and and o2 sensors)

As indicated in an earlier post, it aint gonna be the 3rd o2 sensor because your MR-S wont have one  s:) s:)  (though the connector would've been in that area in a UK model).

There's very little in that area that could trigger a CEL - so my immediate thought was the MAF, and checking that the MAF is seated and sealed properly, connecter fully connected, and that there are no vacuum/air leaks in the system after the MAF.

However, the behavoir of the light (off for a while then on) is typical of a o2 sensor fault code - as most other sensors kick out pretty quickly.
So I would be suspect one of these to be the cause, could be as simple as the connectors not being fully seated, or could have had the wiring or sensor element itself damaged slightly.

I can't remember if the paperclip trick works if you plug the paperclip into the relevant pins whilst the engine is running with the CEL still displayed (rather than plugging in while off and restarting) - this is definitely worth a try if no codes are coming up.

Where are you located? There are now at least 2 people with MR-S code readers now.

[weddallenko]

With the engine running I can feel a bit of blowing where the manifold pipe(s) meet the next section, I didn't really notice the noise until driving to work this morning...
I guess this would contribute to bad readings on the 02 sensors situated just up the pipe a bit...  s:roll: :roll: s:roll:  
I do get a bit of engine popping on deacceleration, but thought that could be a factor of the new manifold. It would make sense don't you think?
Also, the o-ring on the MAF sensor is not a tight fit, it's quite loose. Should it be a flush fit in the recess? If so would you know what size it is off hand? As I'll order some...

Frogger, I'm in Torbay, Devon... Way daaaan Sowf.   s:D s:D

[Anonymous]

With the engine running I can feel a bit of blowing where the manifold pipe(s) meet the next section

This is normal and is the same on mine,the waft is coming from elsewhere(I think its from where the gearbox meets the engine)I doubt its your manifold blowing.

[frogger]

Given what you've said, I wouldn't write off a blowing exhaust entirely, as the symptoms match up...
To get a better idea lightly wet your fingers or forearm or whatever so that you can tell better which direction air is blowing from.

With the engine running I can feel a bit of blowing where the manifold pipe(s) meet the next section, I didn't really notice the noise until driving to work this morning...
I guess this would contribute to bad readings on the 02 sensors situated just up the pipe a bit...  s:roll: :roll: s:roll:

If it is blowing then this can indeed fool o2 sensors:
(o2 sensor thinks, hang on, there's some oxygen knockin about in here - ECU says: hmm, seems i'm too lean, best richen up things a bit with some more fuel...)
and this can easily cause the symtoms your seeing such as codes and excessive popping/backfire.
For this reason when replacing the manifold it is good practice (though not mandatory) to replace the gasket too, to ensure no leasks along your freshly reassembled exhaust system, no matter how minor.

I do get a bit of engine popping on deacceleration, but thought that could be a factor of the new manifold. It would make sense don't you think?

This could be just the manifold (but I doubt it - given that a gutted stock manifold with std exhaust system doesn't backfire unless overfueling when cold).
More likely it's due to overfueling because of blowing, combined with the additional effect that blowing causes - the blowing also provides oxygen into the exhaust to aid the combustion of the surplus fuel (caused by running rich) to create a heftier backfire when it does pop.

Also, the o-ring on the MAF sensor is not a tight fit, it's quite loose. Should it be a flush fit in the recess? If so would you know what size it is off hand? As I'll order some...

Off the top of my head I don't think it should be all that loose. Hopefully someone will come along with a second opinion on that one though!
There's certainly plenty of MR2 roadster MAF pictures on this forum to help you out.

[weddallenko]

Yep, looks like its blown the gasket on the manifold after the o2 sensors... it's quite draft too.
The gasket was replaced when fitted, oh well... I'll get another one on there, tighten it all up and then see if the cel light goes out...
I did the paperclip trick with a bit of single core wire and with the engine running it gave me 2 flashes then 8, code 28... Sound familiar?

First I'll get this blowing exhaust section fixed...  s:roll: :roll: s:roll:  

Thanks again guys.

[frogger]

Yep that code 28 is an o2 sensor code. It usually occurs when one is knackered or unplugged.
To be honest I've never heard of it happening but I supose there's a chance extreme o2 readings could trigger it too, in any case its worth sorting that blowin out, then come back to the sensor issue - it will just waste fuel and sap power!

When i was talking about gasket replacement I meant the manifold>head one - the doughnut type one is usually fine for reuse.

Key thing with that joint is evenly bolting it up. Also I use exhast paste in the joint - sets like rock and takes up any gaps (gaps can sometimes be worse with an aftermarket manifold)

[weddallenko]

Exhaust no longer blowing, I put a new gasket on and wrenched the nuts down tight...
For one thing obviously it sounds much better, however the cel light is still illuminated. Even after disconnecting the battery for half hour... It comes on after about 10 mins.
Is there a chance it could be both o2's or does the code 28 refer to one sensor, if so is which one is it?

[SimonC_Here]

swap them over, clear the code and see if the code changes. if so it was one if not, it was both!  s:) s:)

[frogger]

It's probably only one of them, but I can't remember if the OBD1 system gives different codes for each sensor - pretty sure it does, and IIRC it also gives the SAME code if the sensor is unplugged entirely or if it is knackered, it certainly only gives one code with an unplugged sensor, not multiple ones (tried it myself).

So... Another way of checking without unbolting them is to
- clear the code
- unplug one (try the left hand side one, as I think the right hand side one triggered code 28 with me)
- start things going again.

If you get two o2 sensor codes for different locations (look them up) then chances are left was fine and right one was bad.
Alternatively if you get just the same code, then the one you unplugged was probably the cream crackered one.

Whatever the outcome, reset the code and repeat the test with left one plugged back in, and other (rhs one) unplugged instead to double check the diagnosis and the method.

[weddallenko]

Cheers for the pointers guys..
The car has only just done 60k, so is that a good innings for the 02's? Are they prone to giving up?

Any recommendations where to get some from?

Cheers,

[frogger]

DENSO branded ones for the MR2 Roadster (regardless of the source) are the ones to go for - eBay has a few sellers.

Worth monitoring your oil consumption just in case this has driven the failure (plus it's good practice anyway with these cars!) - however there's been a fair few instances of o2 sensor failing after manifold replacement or precat gutting - the reasons can sometimes be due to dodgy connections (hence me mentioning the connectors in a previous post) or sometimes other damage during the removal / storage / replacement process. It's probably not a coincidence that the manifold replacement and o2 sensor fault happened at the same time.

[Mad Matt]

Got mine via Nathan on this site. Mine went at around the same mileage.

[weddallenko]

Nathan has already pm'd me... pretty much as soon as I created this thread. It's like he's clairvoyant or something!

Like you say its probably no coincidence that they have gone shortly after replacing the manifold, thought I was carefull when they were removed... Oh well..

Oil consumption looked a bit on the high side about 6 months ago, but after an oil change and engine flush it seems to be fine, about 1/2 litre in about 3000 miles.
I hear some 1ZZ can be real oil burners though and anything like a litre in 1000 miles spells doom.

Best get some of these sensors then...

Cheers

[Green Goblin]

While you're on ebay, get a code reader also.

[frogger]

While you're on ebay, get a code reader also.

And then put it straight back on ebay again, because it won't work for your MR-S import !!
Thats exactly why the paperclip technique has been employed throughout this thread.

[weddallenko]

While you're on ebay, get a code reader also.

And then put it straight back on ebay again, because it won't work for your MR-S import !!
Thats exactly why the paperclip technique has been employed throughout this thread.

Well... a paperclip to start with then 2 bits of single core wire soldered to a microswitch so that I can reset the code sequence easily   s:wink: :wink: s:wink:  

I removed both sensors carefully this morning and although quite sooted up, they looked ok (like I would know what a faulty one would look like anyway)...
I figured that if I swapped them over, reset the code and it read back another code entirely then it would be one sensor only... maybe...
Well... after about 15 miles of driving, no light... Got home and parked up. Started the car again and it's back on!
This time with a code 21.. Oxygen sensor.... before it was code 28... No. 2 Oxygen Sensor signal.

Anyone know which sensor is which?

Cheers.

[frogger]

As said in an earlier post, unplug one and see if you still get the same code or two codes.
If you get the same code then the unplugged one is knackered - if you get two codes then it's the one you didn't unplug thats knackered.

The suggestion to swap them over had an inherent flaw in the logic, in so much as you wouldn't know which is dead, as you have discovered   s:wink: :wink: s:wink:  lol
It also risked causing further damage - hence my earlier suggestion of using the unplug method.

Let us know which code ends up relating to each side - will probably be a great help to all MR-S owners in the future!  s:) s:)

[weddallenko]

Guys,

After confirming one (or both) sensors had gone in the MR-S, I thought it to be best to replace both and looked around for places to get them....
Ordered 2 O2 sensors from http://www.automedicsupply.com in the USA, can't remember who recommended that site - someone on here possibly.... but 2 sensors cost  $120.84 - about £78. That's including P&P from California, although I had to pay £23 VAT and customs processing charges - about £102 in total.

They arrived well packaged and within about 12 days, could've been less if our countries infrastructure didn't come to a complete stand still with a bit of snow...
Anyway, they are made by Denso and the part number is 234-4209. They do not come with connectors so you have to use the original ones... included were some 4 x wire crimps and heat shrink sleeves, along with a bit of anti-seize compound...

Installed them both today, very straight forward - driven about 30-40 miles and the warning light hasn't come on since. Jurassic Park!