2002 Toyota Yaris 1.5 T-Sport
Engine code 1NZ-FE

The car suffers from a hesitation when first pulling away after a cold 
start, and occasionaly when changing up a gear. It misfires and feels like 
it will stall, but never does. Once the engine has a slight warmth, the 
problem disappears and the car runs perfectly. This takes about a mile, 
perhaps less, and it revs freely right from the word go, the problem is 
only apparent as one transfers load to the engine. The symptom is very much 
like the way a cold carb fed engine would perform with insufficient choke.

This problem first started when I replaced the OEM Denso plugs with NGKs:

Denso chart recommendation: K16R-U gapped at 0.8mm (that is straight from 
their website. Autodata contradicts this and says to use K16R-U11 with 
1.1mm gap. The car was fitted with K16R-U when I acquired it.)

NGK recommendation: BKR5EY-11 gapped at 1.1mm

So, since they appeared to cause the prob, I removed the NGKs and got a new 
set of Densos, gapped them at 0.8mm, fitted them and the problem 
disappeared. For about 2k miles. Now, it has returned, yet the plugs are 
still like brand new and the gaps are still correct. Deposits are the 
normal light grey, with no fouling or evidence of poor combustion.

Could it be that the plugs are a red herring and the car has some other 
problem? Checks I have done so far are:


- Checked for intake air leaks using soapy water. Found none.
- Measured coil resistances, all four are between 21 and 23K
- Checked readout from CTS via OBD scan. Reads normally, i.e. around 
ambient temp when cold, rising to 80-90deg warmed up.
- Checked intake air temp readout as above. Reads ambient temp with a cold 
engine.
- Checked for any stored DTCs. None present.
- Measured TPS voltage: 0.54V closed, rising to 3.87V at WOT. No dead 
spots.

Any other ideas, please? It's a very small issue but doesn't seem right for 
an EFi car.

On Fri, 06 Nov 2009 16:29:10 -0000, Stu  wrote:

> 2002 Toyota Yaris 1.5 T-Sport
> Engine code 1NZ-FE
>
> The car suffers from a hesitation when first pulling away after a cold
> start, and occasionaly when changing up a gear. It misfires and feels  
> like
> it will stall, but never does. Once the engine has a slight warmth, the
> problem disappears and the car runs perfectly. This takes about a mile,
> perhaps less, and it revs freely right from the word go, the problem is
> only apparent as one transfers load to the engine. The symptom is very  
> much
> like the way a cold carb fed engine would perform with insufficient  
> choke.
>
> This problem first started when I replaced the OEM Denso plugs with NGKs:
>
> Denso chart recommendation: K16R-U gapped at 0.8mm (that is straight from
> their website. Autodata contradicts this and says to use K16R-U11 with
> 1.1mm gap. The car was fitted with K16R-U when I acquired it.)
>
> NGK recommendation: BKR5EY-11 gapped at 1.1mm
>
> So, since they appeared to cause the prob, I removed the NGKs and got a  
> new
> set of Densos, gapped them at 0.8mm, fitted them and the problem
> disappeared. For about 2k miles. Now, it has returned, yet the plugs are
> still like brand new and the gaps are still correct. Deposits are the
> normal light grey, with no fouling or evidence of poor combustion.
>
> Could it be that the plugs are a red herring and the car has some other
> problem? Checks I have done so far are:
>
>
> - Checked for intake air leaks using soapy water. Found none.
> - Measured coil resistances, all four are between 21 and 23K
> - Checked readout from CTS via OBD scan. Reads normally, i.e. around
> ambient temp when cold, rising to 80-90deg warmed up.
> - Checked intake air temp readout as above. Reads ambient temp with a  
> cold
> engine.
> - Checked for any stored DTCs. None present.
> - Measured TPS voltage: 0.54V closed, rising to 3.87V at WOT. No dead
> spots.
>
> Any other ideas, please? It's a very small issue but doesn't seem right  
> for
> an EFi car.

Plug leads?

On Fri, 06 Nov 2009 16:29:10 -0000, Stu  wrote:

> 2002 Toyota Yaris 1.5 T-Sport
> Engine code 1NZ-FE
>
> The car suffers from a hesitation when first pulling away after a cold
> start, and occasionaly when changing up a gear. It misfires and feels  
> like
> it will stall, but never does. Once the engine has a slight warmth, the
> problem disappears and the car runs perfectly. This takes about a mile,
> perhaps less, and it revs freely right from the word go, the problem is
> only apparent as one transfers load to the engine. The symptom is very  
> much
> like the way a cold carb fed engine would perform with insufficient  
> choke.
>
> This problem first started when I replaced the OEM Denso plugs with NGKs:
>
> Denso chart recommendation: K16R-U gapped at 0.8mm (that is straight from
> their website. Autodata contradicts this and says to use K16R-U11 with
> 1.1mm gap. The car was fitted with K16R-U when I acquired it.)
>
> NGK recommendation: BKR5EY-11 gapped at 1.1mm
>
> So, since they appeared to cause the prob, I removed the NGKs and got a  
> new
> set of Densos, gapped them at 0.8mm, fitted them and the problem
> disappeared. For about 2k miles. Now, it has returned, yet the plugs are
> still like brand new and the gaps are still correct. Deposits are the
> normal light grey, with no fouling or evidence of poor combustion.
>
> Could it be that the plugs are a red herring and the car has some other
> problem? Checks I have done so far are:
>
>
> - Checked for intake air leaks using soapy water. Found none.
> - Measured coil resistances, all four are between 21 and 23K
> - Checked readout from CTS via OBD scan. Reads normally, i.e. around
> ambient temp when cold, rising to 80-90deg warmed up.
> - Checked intake air temp readout as above. Reads ambient temp with a  
> cold
> engine.
> - Checked for any stored DTCs. None present.
> - Measured TPS voltage: 0.54V closed, rising to 3.87V at WOT. No dead
> spots.
>
> Any other ideas, please? It's a very small issue but doesn't seem right  
> for
> an EFi car.

Or more relevantly, try looking under the hood in the dark & seeif you can  
see any tracking from the coils

Stu wrote:
> 2002 Toyota Yaris 1.5 T-Sport
> Engine code 1NZ-FE
>
> The car suffers from a hesitation when first pulling away after a cold
> start, and occasionaly when changing up a gear. It misfires and feels
> like it will stall, but never does. Once the engine has a slight
> warmth, the problem disappears and the car runs perfectly. This takes
> about a mile, perhaps less, and it revs freely right from the word
> go, the problem is only apparent as one transfers load to the engine.
> The symptom is very much like the way a cold carb fed engine would
> perform with insufficient choke.
>
> This problem first started when I replaced the OEM Denso plugs with
> NGKs:
>
> Denso chart recommendation: K16R-U gapped at 0.8mm (that is straight
> from their website. Autodata contradicts this and says to use
> K16R-U11 with
> 1.1mm gap. The car was fitted with K16R-U when I acquired it.)
>
> NGK recommendation: BKR5EY-11 gapped at 1.1mm
>
> So, since they appeared to cause the prob, I removed the NGKs and got
> a new set of Densos, gapped them at 0.8mm, fitted them and the problem
> disappeared. For about 2k miles. Now, it has returned, yet the plugs
> are still like brand new and the gaps are still correct. Deposits are
> the normal light grey, with no fouling or evidence of poor combustion.
>
> Could it be that the plugs are a red herring and the car has some
> other problem? Checks I have done so far are:
>
>
> - Checked for intake air leaks using soapy water. Found none.
> - Measured coil resistances, all four are between 21 and 23K
> - Checked readout from CTS via OBD scan. Reads normally, i.e. around
> ambient temp when cold, rising to 80-90deg warmed up.
> - Checked intake air temp readout as above. Reads ambient temp with a
> cold engine.
> - Checked for any stored DTCs. None present.
> - Measured TPS voltage: 0.54V closed, rising to 3.87V at WOT. No dead
> spots.
>
> Any other ideas, please? It's a very small issue but doesn't seem
> right for an EFi car.


you cannot check for inlet leaks with soapy water, the leak will be sucking, 
not blowing, check for inlet leaks using a flammable liquid or gas, carb. 
cleaner is convenient with the engine running, any leaks that you spray over 
will cause a speed variation.

running the larger gap may have caused a tracking issue, which may have 
damaged one or more coils.

> > The car suffers from a hesitation when first pulling away after a cold
> > start, and occasionaly when changing up a gear. It misfires and feels  
> > like it will stall, but never does.
> Plug leads?

I finally got around to replacing my plug leads last week, after 
putting up with my ageing Hyundai Accent doing exactly the same thing 
for a few months.

Changing the leads appears to have sorted it :-)

Colin Wilson wrote:
>>> The car suffers from a hesitation when first pulling away after a
>>> cold start, and occasionaly when changing up a gear. It misfires
>>> and feels like it will stall, but never does.
>> Plug leads?
>
> I finally got around to replacing my plug leads last week, after
> putting up with my ageing Hyundai Accent doing exactly the same thing
> for a few months.
>
> Changing the leads appears to have sorted it :-)

I have an idea that the Yaris does not have any plug leads, but ICBW

On Fri, 06 Nov 2009 23:22:32 -0000, Mrcheerful   
wrote:

> Colin Wilson wrote:
>>>> The car suffers from a hesitation when first pulling away after a
>>>> cold start, and occasionaly when changing up a gear. It misfires
>>>> and feels like it will stall, but never does.
>>> Plug leads?
>>
>> I finally got around to replacing my plug leads last week, after
>> putting up with my ageing Hyundai Accent doing exactly the same thing
>> for a few months.
>>
>> Changing the leads appears to have sorted it :-)
>
> I have an idea that the Yaris does not have any plug leads, but ICBW
>
>

I think it's coil on plug, but they track as well.

-- 
Duncan Wood

"Mrcheerful"  wrote in
news:AsYIm.2302$Ym4.75@text.news.virginmedia.com: 
>
> you cannot check for inlet leaks with soapy water, the leak will be
> sucking, not blowing, check for inlet leaks using a flammable liquid
> or gas, carb. cleaner is convenient with the engine running, any leaks
> that you spray over will cause a speed variation.
> 
> running the larger gap may have caused a tracking issue, which may
> have damaged one or more coils. 
> 
> 
Thanks for your replies. The ignition is indeed coil-in-cap. I'll start it 
under cover of darkness in a couple of days (working nights right now)and 
look for any evidence of tracking. At the same time, I'll also check again 
for air leaks with whatever flammable spray I can lay my hands on. ;-)

Stu  wrote in
news:0vednX1xHqnkhWjXnZ2dnUVZ7qadnZ2d@brightview.co.uk: 

Update

Checked under the bonnet in darkness and nothing is glowing. Done another 
check for leaks with a flammable spray and nothing happened. The only idea 
I have left is to disable the fuel pump and try the coils on a spare plug, 
looking for a weak spark. Any other theories?

Stu wrote:
> Stu  wrote in
> news:0vednX1xHqnkhWjXnZ2dnUVZ7qadnZ2d@brightview.co.uk:
>
> Update
>
> Checked under the bonnet in darkness and nothing is glowing. Done
> another check for leaks with a flammable spray and nothing happened.
> The only idea I have left is to disable the fuel pump and try the
> coils on a spare plug, looking for a weak spark. Any other theories?

it is extremely difficult to see a tracking spark on 'coil on plug' 
vehicles, and in any case if the misfire only occurs when the engine is 
loaded (ie not when ticking over then there will be nothing to see in any 
case.)

I would try a scrupulous clean of each coil pack  and spray it well with 
wd40, clean the outsides of the plugs well too, and then try it, if there is 
an improvement then you are on the right track (no pun intended)  the other 
problem is that the coil may be tracking internally like mondeo ones do and 
then the only way is to substitute with a known good pack.

there is also the possibility that the fault lies somewhere else completely, 
such as a tdc sensor.

On Mon, 09 Nov 2009 21:19:00 GMT, "Mrcheerful" 
wrote:

>it is extremely difficult to see a tracking spark on 'coil on plug' 
>vehicles, and in any case if the misfire only occurs when the engine is 
>loaded (ie not when ticking over then there will be nothing to see in any 
>case.)
>
>I would try a scrupulous clean of each coil pack  and spray it well with 
>wd40, clean the outsides of the plugs well too, and then try it, if there is 
>an improvement then you are on the right track (no pun intended)  the other 
>problem is that the coil may be tracking internally like mondeo ones do and 
>then the only way is to substitute with a known good pack.
>
>there is also the possibility that the fault lies somewhere else completely, 
>such as a tdc sensor. 
>

Thanks, Mr Cheerful

I'll do as you suggest and see if I can get any noticable improvement.
Failing that, I don't think it's worth getting into advanced
diagnostics to try and solve a very small driveability issue that only
affects a completely cold engine. I'll wait and see what develops. ;-)

Cheers,

Stu