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Old 11-21-2003, 01:10 PM
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Cold start and EGR issues

Hello All,

I just got the E320 back from the Shop, Replacement of head gasket and all that goes with this type of repair. Car has 208K on it, and according to all information available this would be the first time for the head gasket. Before, I take it back to have them look into the below. I need to know what , why and that I can't repair it.

That said, I Need some insight on troubleshooting problems with My 1996 E320. Before, I list the symptoms, yes I have done searches on the Tech Help forum. Quite a bit of information was found. I'll be running test on the EGR Valve. I'll so be testing the cold start injectors, still have to find the procedures.

Here goes…

Symptoms :

Check engine electronics displayed ( check engine light Not On? ), Code PO400 EGR Valve.
Engine Idles a little rough, Removal of vacuum hose to EGR value, car idles smooth.
Cold start issues, car cranks but does not start until depressing gas peddle.
Once Car has started once it will restart Fine until it Sits for about 20 to 30 min.

Any Insights on Items to check, verify.
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Old 11-21-2003, 08:18 PM
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Join Date: Mar 2003
Location: Southern California
Posts: 2,011
The EGR should not be open during cold start or when the engine is idling, hot or cold. It should only opens during "cruise" operation.

It sounds like the EGR valve is functional, but something is amiss in the control system. I'm not familiar with the specifics of the EGR control system for your model, but if this problem only started when you got the car back from the head rebuild, my first guess would be someone forgot to hook up an electrical connector or vacuum line, or misconnected same.

It's possible that once the EGR situation is corrected the cold start issue may go away.

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Old 11-21-2003, 08:18 PM
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Join Date: Mar 2001
Location: Evansville WI
Posts: 9,616
The 104 motor has no "cold start injectors"
If the engine runs smoothly if you disconnect the vac hose to the EGR valve, then one would suspect that vacuum is being applied inappropriately to the EGR valve.
There are 2 switch-over valves on the front of the cylinder head cover, one is EGR, the other is for the AIR pump divert valve. The AIR pump divert valve will activate on engine stat-up IF the engine temp is cold enough. I suspect that either A) the wiring was put on the switch-over valves reversed, or B) the vacuum hoses were put onto the wrong switch-over valves.
Other possiblities is that the engine control module is "whacked" shall we say, or there is a short in the harness somewhere causing the EGR switch-over valve to apply vacuum to the valve. More than likely it is A or B listed above.

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Old 11-21-2003, 11:38 PM
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Duke & Gilly,

Thanks for the information, I'll Check into
the items mentioned. You have also
confirmed a few items with the operation of the EGR
at idle.

Gilly- Thanks, would have be looking for
something not there.
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Old 11-22-2003, 05:24 AM
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Join Date: Mar 2001
Location: Evansville WI
Posts: 9,616
Just don't try reversing the wires AND the hoses, then you'll have the same situation. Try looking at it to see if it appears one or the other may be reversed (doesn't look quite right). I think it's physically possible to reverse either one of these. The switch-over valves themselves are interchangeable with each other, same part.

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Old 11-22-2003, 08:54 AM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
Yea, I would guess the vacuum lines from the switch-over valves are reversed.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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Old 11-22-2003, 05:11 PM
Posts: n/a
Well Just got done looking it over and found the
vacuum line to the check valve switched with the vacuum line
to the EGR at the switch over valve, corrected vacuum lines.

Cold start problem, rough idle, and EGR trouble
code po400 no longer an issue :).

However, I am getting a po170 :(. Other
Than this, car runs great. Would the system
require time to adjust?
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