[W126 Coupe] Hesitation on Start

[Dick Spellman]

Hi Gary:

Test the new injectors and seals for leaks using just a spray bottle of 
water around each unit and line to be sure there is no air seepage.  
Engine idle would 'change' if a leak were detected where the water was 
sucked in.

Were there any hardened rubber components or rigid vacuum line and 
fittings that you had to move during the fuel injector replacement?  
Again, the spray bottle of water applied to vacuum lines and hoses may 
turn up a leak.  A vacuum guage hooked up to the intake manifold may 
help in reading a small leak while spraying the water but, it's going to 
be erratic where you have the poor idle anyway.  Just might go stable 
for a bit if the water hits the right spot temporarily sealing the leak.

On the EHA, simply look for visible signs of leakage or wetness.  This 
is done with air cleaner removed, engine running and you should see a 
film of fuel or feel with your fingers for fuel at the base top and 
sides of the EHA.  I think this unlikely since you have not noted a fuel 
smell in the past.  There is no reason to adjust the eha at this time, 
so I'd leave it alone.

Tackling a problem that existed like this is possible but, you need to 
do the troubleshooting (not guessing, replacing) in an organized fashion 
in order to get to the route of the problem.  I am by no means an expert 
but, I have spent considerable time learning how to check fully the 
electrics side of the car (rotor, cap, wires, coil, plugs, O2 sensor) 
followed by the more difficult side which is the air/fuel side.

So, taken at first glance it appears your electrics are in order and 
renewed.
What is the part # on the new spark plugs you installed?  The reason I 
ask is that the factory recommended plug ONLY has 1 electrode.  Many 
autoparts people just hand you the plugs and they are 4 electrodes or 
something other than the factory recommended, ONE.  The multiple 
electrode plugs are known to cause problems.  So, I do not recommend them.
Have you replaced the O2 sensor and how many miles ago?  The )2 is part 
of the engine management system and influences the lambda (lean/rich).  
If it becomes fouled (from oil seepage over a long period of time) or 
from more than 60k miles of driving or from using anything other than 
Premium fuel, it needs to be replaced.
Fuel filter replacement done?  Unlikely that this is the cause of your 
troubles but, if filters are more than 30k miles, replace them.
Gas cap on tight and seal good? (You hear the air sucked in on first 
opening?)

The cold start injector test assures that the coolant temp sensor is 
providing a signal to the electronic idle speed control which in turn 
enriches the fuel mixture by firing the cold start injector during 
warm-up.  On the 4-pin coolant sensor it will also operate the clutch on 
the air pump for a period of time.  I am told the injector itself does 
not routinely fail.  So, this is nothing more than a 5-minute test of 
the sensor and wire harness as the engine goes from cold to warm.  And 
it is one of many steps from 07.3 that you 'll need to perform.  I did 
the easiest ones first because I was new at the process and did not have 
all of the equipment they lay out for some of the procedures.  All I 
really need to know is that it's providing fuel at cold start and not 
continuing to pump after the 60C temp is reached.

By the way, what is the idle speed when warmed up and in park?
Do you just feel a constant stumble or is it an occasional miss?
Does the idle raise slightly when you kick in the AC, does it smooth out 
at all with ac on?
Are you able to depress the gas pedal slightly to raise the idle and 
smooth the engine out at say 900-1000rpm?

You are going to check one or all of these items...your air slider valve 
and hoses, the Throttle Position Sensor at idle, take a reading of the 
existing lambda, check the control piston for signs of leakage after you 
report back on the above questions.  You may just feel better giving me 
a call first as the above looks worse than it really is.

Regards,

Dick
508-641-8477 (my cell if it goes to VM, just leave a call back #) Boston

Kirby, Alan (MED US) wrote:

> Dick,
> Wires are Beru; plugs, cap & rotor are Bosch
> How do you check the cold start injector?
> The engine does not smell rich on cold start
> The car starts slightly faster on cold start if I depress the 
> accelerator slightly, but not the same as before.
> I did the work.
>  
> The engine has a rough idle after warming up. This condition existed 
> prior to the tune up and injector work.
>  
> Gary Peck commented in another reply to my initial question:
>  
> I had the same problem, turns out it was a defective EHA regulator, 
> the o rings may be shot, try replacing them first then test for leaks, 
> 90% odds you will have to replace the EHA not cheap retails for 
> $270.00 in Canada.
>  
> What do you think now?
> Thanks in advance for your time and expertise,
> Alan
>  
>  
> *From*: Dick Spellman ^lt;/no email/>
> *Date*: Wed Aug 30 2006 - 16:12:11 EDT
>
> Hi Alan:
>
> A few questions.
>
> Can you provide a list of the mfg. components used for the plugs, wires,
> cap and rotor?
> Have you checked to see if the cold start injector is firing when the
> engine is cold?
> Does the engine smell like it's rich on a cold start?
> Does the car start faster when you depress the accelerator a bit while
> cold cranking?
> How's the engine run at idle after a cold start and after having 
> warmed up?
> Did you do the work or an independent shop?
>
> Regards,
>
> Dick
>
> Kirby, Alan (MED US) wrote:
>
> /> 1989 560 SEC /
> /> 119k miles /
> /> /
> /> Recent changes: /
> /> Replaced plugs (gap at .039), wires, rotor, cap and air cleaner /
> /> Replaced injectors, holders, ands seals /
> /> /
> /> The car used to start on the first turn over of the engine. Now when /
> /> it's cold, it starts on about the third turnover of the engine. /
> /> When it's warm, it usually starts on the first turnover. /
> /> /
> /> Any ideas?? /
>
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