Hi all,

I started a thread in February titled "Idle speed on '87 300e"

http://www.peachparts.com/shopforum/tech-help/180499-idle-speed-87-300e.html#post1431147

where I got some advice to increase my idle by shorting a purple fuel injector computer wire to ground.

I've run into several problems that may or may not be related concerning the idle speed modification. I did perform the splicing of the purple wire to the thickest solid brown wire that I confirmed was a ground. (There were several solid brown wires in the bundle, but I confirmed that the thickest one did go to ground - I don't know where the other ones go.) This did seem to pick my idle up slightly and solved my 0 to anything smoothness. Shortly afterward (but not immediately) I noticed that my mixture had gone off the deep end rich and my starter would not immediately disengage from the flywheel when starting, leading to a dreaded grinding noise. I changed the starter with a rebuilt unit with no effect.

I started a thread on the mixture problem where we discussed EHA adjustment and coolant temp testing. I tried the EHA with no luck, the O2 sensor is new and the temp sensor tested fine. I don't have time right now to learn the whole fuel injection system so I broke down and took it to our local MB (non-stealer) shop. I told my mechanic about my purple to brown wire splice and my starter and mixture problems. After much testing he cut the splice and my starter problem went away but it had no effect on the mixture. He performed many tests but bottom line he was not getting enough fuel pressure (which seems backwards to me - low pressure seems like it would be lean - I'll admit ignorance here). He was getting the right mixture at idle but at anything above about 2500 RPM it went way too rich. His recommendation is to buy a new fuel distributor. He knows I'm capable of this so he left it to me to do to save money. Since I've got 8 hours of labor to get this far he said he'd adjust the mixture for free once I change the distributor.

Ok - questions:

My mechanic couldn't get the right fuel pressure, could the problem be the fuel pressure regulator? He said fuel pumps (2 on mine) tested fine.

Or does the distributor sound right?

I don't mind buying what I need, I just don't want to buy what I don't need.

Thanks as always,

Bob

'67 TR4a
'76 GMC C15
'85 XJ-6
'87 300e
'97 VW Cabrio