Working on a few small problems with my SE.

1. Have a surging on deceleration (like an abrupt on/off throttling). I am thinking I need a new deceleration microswitch. Is this part plug n play?

2. Oil Pressure takes a few seconds to rise on cold start. Maybe 4 seconds. I can hear lifter clatter while before pressure rises. Once oil pressure pegs, idle drops to 750 now, from 1000. Any thoughts? Thinner oil? Time for synthetic? New Lifter(s)?

3. This problem may be more complicated. Car stumbles when the temp gauge is between 55C and 80C in the morning. When restarting after engine is hot (80C), I have major hesitation for a few minutes. Goes away and afterwards everything is fine- pulls smoothly to 6500 in all gears

DC is ~50%. 49% in open loop.

Any advise? I have a hankerin' for some tinkerin'.

__________________
'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

Disable the EHA and drive it temporarily to see if the problem goes away. That way you will know if it is mechanical or electrical. If after disabling the EHA you still have the problem then obviously it has nothing to do with the EHA.

You can disable the system by simply disconnecting the O2 sensor. You will get a check engine light, but it will go away when you reconnect it. Be careful with any connector that you remove because the car is 15 years old or so and they can be brittle.

Your oil pressure worries me. Has this engine had frequent oil changes, how many miles, how has it been driven?

Good luck,

Thanks Larry,

Instead of removing the 02 sensor, can I just unplug the EHA?

Oil changes have always been 5k or less. Complete valve job ~1.5 years ago.

Thanks Mike

__________________
'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

Yes, unplugging the EHA is probably the more common way to disable it.

Good luck,

[QUOTE]Originally posted by fahrgewehr2
[B]Working on a few small problems with my SE.

2. Oil Pressure takes a few seconds to rise on cold start. Maybe 4 seconds. I can hear lifter clatter while before pressure rises. Once oil pressure pegs, idle drops to 750 now, from 1000. Any thoughts? Thinner oil? Time for synthetic? New Lifter(s)?

I own a '91 300SEL - live in a warm climate.

My oil pressure needle finally jumps on cold start 1st thing in the am after running for about 1.5-2.0 secs. I bought the car in '97 with 35,000 on the odometer. It now has 115,000.

Oil gets changed every 2500 or so. Castrol 10W-40 GTX + either Mann, Mahle-Knecht; Hengst oil filter.

FYI

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

mike.. check your PM

Hi,

Snibble- never got a pm?

I will check on somethings tonight and post my findings.

Mike

__________________
'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

lol oops... I guess there were 2 mikes. I meant the other Mike... I sent him a PM a few days ago, wasn't sure if he read it or not. Sorry for the mix up

Drove the car sans EHA control as per LB's advise.

car drove terribly- stuttering, hesitating no matter the engine temp. Same exact things I experience in the morning when the temp gauge is between 50- 75.

hmm.

THIS thread details the problem further.

__________________
'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E