90 300SE Start / idle problems
Thread Starter
Member
Joined: Jun 2003
Posts: 130
Likes: 0
From: Northeast MA
1990 300SE
90 300SE Start / idle problems
Hi,
The car is a 1990 300SE with 189,000 miles
This past winter the car would not start in the
morning when it was about 15 degrees F or lower out.
Car would turn over but would not start. On 3
occasions I had to add 2-3 bottles of dry gas each
time for it to start. Also recently the engine seems
to start rough in normal weather and idles roughly.
Once the car is going about 10mph it is as smooth as
glass without any hesitation, surging or misfires.
Engine does not smoke at all. Changed out fuel filter
and that did not help. Platinum plugs, wires rotor
and cap were replaced about 60,000 miles ago. New air
filter, EGR valve and O(2) sensor on 11/02,
When my car was in for an alignment at my local MB
dealer, I had them check out the car’s problem. An
initial diagnosis was performed but the technician ran
out of time. Below is what was written on the service
receipt.
“Performed lambda test, found intermittent
reading-possible control module for cold start
problem, may need fuel distributor and injectors,
possible coil”
what and where is the control module? Is it the engine
computer?
What are the symptoms for replacing a fuel
distributor? That is one expensive part!
When should injectors and a coil be replaced?
I figured the coil is fine because there is no problems
at above idle speeds.
Any help is appreciated, I really do not want to put
much more money into this car.
The car is a 1990 300SE with 189,000 miles
This past winter the car would not start in the
morning when it was about 15 degrees F or lower out.
Car would turn over but would not start. On 3
occasions I had to add 2-3 bottles of dry gas each
time for it to start. Also recently the engine seems
to start rough in normal weather and idles roughly.
Once the car is going about 10mph it is as smooth as
glass without any hesitation, surging or misfires.
Engine does not smoke at all. Changed out fuel filter
and that did not help. Platinum plugs, wires rotor
and cap were replaced about 60,000 miles ago. New air
filter, EGR valve and O(2) sensor on 11/02,
When my car was in for an alignment at my local MB
dealer, I had them check out the car’s problem. An
initial diagnosis was performed but the technician ran
out of time. Below is what was written on the service
receipt.
“Performed lambda test, found intermittent
reading-possible control module for cold start
problem, may need fuel distributor and injectors,
possible coil”
what and where is the control module? Is it the engine
computer?
What are the symptoms for replacing a fuel
distributor? That is one expensive part!
When should injectors and a coil be replaced?
I figured the coil is fine because there is no problems
at above idle speeds.
Any help is appreciated, I really do not want to put
much more money into this car.
MBWorld Fanatic!
Joined: Aug 2002
Posts: 1,005
Likes: 33
From: Germany
'00 S320 W220, '98 A160 W168/ sold in 2005 '86 260 E W124 '90 260E W124
Hard to tell from remote. But what the mechanic said seems not too far out, but needs further investigation. The distributor is expensive. There are some more causes:
*leaky injections valves
*not properly working (leaky and/or not working) cold start valve
*Cold start computer does not tell me anything, but the motor management is sort of a computer and controls also cold starts
*The coils thing was an advise from MB already, in a similar case, but I had no proof for that being right.
*Fuel pump can also cause problem at starting. There is a backflow preventing valve on the fuel pump to keep fuel pressure up for some time for easier starting. If this is gone and the pressure reduces too quick it can also be a cause. But normally only when warm engine wont start after parking for some time (2-4 hours or so).
*rough idle and hesitating starting can also be caused by broken injector seals. To this, take off the airfilter, let the engine run at idle and spray alcohol or lighter fuel on the injector seals. If the idle speed increases there is a leak for extra air entering. You can also test all the rubber hoses and vacuum lines to the engine for leaks.
*leaky injections valves
*not properly working (leaky and/or not working) cold start valve
*Cold start computer does not tell me anything, but the motor management is sort of a computer and controls also cold starts
*The coils thing was an advise from MB already, in a similar case, but I had no proof for that being right.
*Fuel pump can also cause problem at starting. There is a backflow preventing valve on the fuel pump to keep fuel pressure up for some time for easier starting. If this is gone and the pressure reduces too quick it can also be a cause. But normally only when warm engine wont start after parking for some time (2-4 hours or so).
*rough idle and hesitating starting can also be caused by broken injector seals. To this, take off the airfilter, let the engine run at idle and spray alcohol or lighter fuel on the injector seals. If the idle speed increases there is a leak for extra air entering. You can also test all the rubber hoses and vacuum lines to the engine for leaks.
