[W126 Coupe] 87 560SEC (euro) running problems

[Jonathan Hodgman]

Al,
What's yer duty cycle @ idle?  Mv's @ the EHA?  Have you checked fuel 
pressures?

If you want something quick and dirty to check swap in another 560 or 
420 KE control unit..  it'll work Well Enough as to see if your original 
bit is freaking out.

Lemme know!
On 6/7/2011 11:51 AM, alal30319 at gmail.com wrote:

> Jay

>

> Thanks, the plugs are good and on tight. I would not expect it to be 

> the plugs because if it was a bad one, you would usually see a 

> constant miss. In this case, it can be smooth on startup, but then act 

> out after a drive which is why i'm thinking that it may be o2 sensor 

> or computer related.

>

>

> On Mon, Jun 6, 2011 at 6:18 PM, Jay Hirsch <j.hirsch at mac.com 

> <mailto:j.hirsch at mac.com>> wrote:

>

>     Just a suggestion

>

>     Pull the plugs  and put them back in making sure each one is in

>     fact screwed all the way in

>

>     Jay H

>     On Jun 6, 2011, at 5:59 PM, alal30319 at gmail.com

>     <mailto:alal30319 at gmail.com> wrote:

>

>     > All

>     >

>     > I posted this on a couple of forums but i've not been able to

>     get any tangible answers so I thought I would cross post here:

>     >

>     > Here is my scenario:

>     >

>     > When I bought this car, I got it to run like a scalded ape. It

>     was fast and smooth. I replaced the plugs (NGK non resistor), plug

>     wires, coil, rotor and crank position sensor.

>     >

>     > Recently, I had a bad miss which I've been trying to chase down.

>     I initially thought it was a bad fuel distributor or injectors

>     caused by bad gas, so I pulled the injectors and checked them.

>     Some of them were a little weak so I replaced all 8 and got the

>     car to run very well at idle. But after running the engine for a

>     while, it would develop a miss on and off and you'd see the oil

>     pressure gauge drop when it does.

>     >

>     > After a long drive, the miss would get worse and become more

>     constant.

>     >

>     > I've been able to disconnect the electrical connection to the

>     EHA and get the car to idle better.

>     >

>     > I've checked for vacuum leaks but could not find any. The vacuum

>     gauge on the dash is pinned to the left until the car develops a

>     miss and then it will move towards the center (about 1/2 way

>     between far left and center).

>     >

>     > I swapped out the EHA with another that I had on shelf but this

>     did not change the symptoms.

>     >

>     > I suspect that it could be the O2 sensors, or the computer

>     trying to lean out the mixture but I am not sure how to test these.

>     >

>     > I'd be grateful for your thoughts.

>     >

>     > The MB Coupes Website!

>     > W126 SEC Mailing List

>     > Postings remain property of MB Coupes, L.L.C.

>

>     The MB Coupes Website!

>     W126 SEC Mailing List

>     Postings remain property of MB Coupes, L.L.C.

>

>

>

> The MB Coupes Website!

> W126 SEC Mailing List

> Postings remain property of MB Coupes, L.L.C.


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