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

[alal30319 at gmail.com]

Bellamy

The coil is new, I don't think it is the coil because disconnecting the EHA
would not fix bad coil. I think I need to do a bid of diagnoses. I'll take
everybody's suggestions and do more diagnoses on the car this weekend.

Thanks for your help.


On Wed, Jun 8, 2011 at 3:57 PM, Mister McGoo <eelploot at hotmail.com> wrote:


>  Al,

>

> Restricted exhaust would cause steady drop in vacuum but so would retarded

> ignition timing.   MacBain's suggestion would fit.  A faulty coil will heat

> and take spastic fits (or simply pack in) and of course is connected to the

> Ignition Control Module.  Randomly confused ignition, lower RPM, lower

> vacuum and lower oil pressure.  You have access to a coil to swap in?

>  Cheaper than the Module for sure! ($2,000+)

>

> -Bellamy

>

> ------------------------------

> Date: Tue, 7 Jun 2011 11:47:21 -0500

>

> From: alal30319 at gmail.com

> To: mbcoupes at mbcoupes.com

> Subject: Re: [W126 Coupe] 87 560SEC (euro) running problems

>

> Bellamy

>

> Thanks for responding, the vac and oil pressure drops only during the miss

> and they come right back (in the case of the oil pressure, it actually drops

> on every miss and comes back). When driving, the oil pressure is pinned at 3

> bar. Engine temp is around 80.

>

> The car has dual manifolds going into a two in two out cat in the center of

> the car.

>

> I'll try disconnecting the 02 sensors and see what it does.

>

> With best regards

>

> Al Abbasi

>

>

> On Tue, Jun 7, 2011 at 11:19 AM, Mister McGoo <eelploot at hotmail.com>wrote:

>

>  alal30319...name?

>

> With the limited information, ideas are somewhat shots in the dark.  The

> "economy" gauge acts as a poor excuse vacuum gauge but a vacuum test is a

> good place to start.

>

> I assume that the oil pressure drops at idle because the RPM's drop

> somewhat due to the missing.  Or does the oil gauge read something LESS than

> 3+bar at higher RPM when driving?  What about engine temperature... is it

> abnormally high at the same time?

>

> The fact that the vacuum drops as the engine heats up possibly indicates a

> restricted exhaust system.  Does the [euro] car have catalytic converters?

>  [assume yes with 02 sensors?] Twin exhaust? [like earlier euro 500 & 380?]

>  Or secondary cat in single system??

>

> -Bellamy

>

> ------------------------------

> Date: Tue, 7 Jun 2011 10:51:26 -0500

> From: alal30319 at gmail.com

> To: mbcoupes at mbcoupes.com

> Subject: Re: [W126 Coupe] 87 560SEC (euro) running problems

>

>

> 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> 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 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.

>

> 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.

>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.pairlist.net/pipermail/mbcoupes/attachments/20110608/48ae6e6f/attachment.htm>