Continued from: Getting too long and disorganized. Let's stick on topic this time Tons of informative pictures on head removal, throttle body and a bunch of other stuff.



How it drives:
Idles rough, but as soon as you touch the throttle it disappears. Performance is slower than should be (car driven by another 300TE owner). Can't feel any misfiring when accelerating...its all at idle.

Static Tests:
-Throttle Plate adjusted + centered correctly.
-Fuel Pressure perfect (5.4bar 4.9bar + holds 3bar after 30mins on specs)
-Airflow Potentiometer reads .7v, dead on specs.
-No error codes
-No vacuum leaks
-Mixture tried/set all different configurations. Settled with 50%
-Compression perfect.
-EZL reads 85% engine off ignition on. WOT reads 20%
-I get ~15MPG average so fuel economy lower than it should be. With 140miles Freeway, 30miles City I get 17MPG.
-Slower than the car should be performance-wise

Parts swapped/replaced:
Precats hollowed out, New Main Catalytic Converter.
New OVP
New Coolant Temperature Sensor
New Voltage Regulator
New Injector's+Seals
New Non-Resistor H9DCO's Spark Plugs
New Ignition Wires (checked for arching as well)
New Distributor Rotor + Cap
New Fuel Filter
New Breather Hoses
New Ignition Coil
New O2 sensor
New Motor Mounts
New Head gasket + valve job -- Compression 190psi across the board.
Swapped Jetronic Brain /w used one
Swapped Fuel Pump Relay /w used one
Swapped Cold Start Valve /w used one (in case it was leaking)
Swapped EZL /w used one

I don't understand why I still have this rough idle
Many of you have helped me through this and a lot of the things I have replaced were bad/old or improved the engine in some way or another so I don't feel bad spending the money...I just want my smooth idle!!

I don't know if there any more static tests I can do on this? Honestly what the hell is left that could be causing this??

Not sure where to go from here....

I don't know if I should just take it to the dealership? I'm afraid they wont find anything as I have gone over much of the stuff they will check for...?

Can I rule off the fuel distributor if the fuel pressure is okay?

 

A few pictures so you can see cleanliness and general condition of engine.

 

Have you tried another fuel distributor?

 

A while back I swapped it out...but I have done a lot since then.

 

here's a guy who swears by fuel distributor replacement, although different symptoms to yours http://www.mercedesshop.com/shopforu...ight=idle+w124

 

^ Interesting.

I have two other fuel distributors from the junkyard i got dirt cheap a while back...
I'll swap each each one of them and see if it makes any difference.

Gonna take this one step at a time for now. I'll do this first before doing anything else.

 

Make sure you replace the O ring under the fuel distributor because they leak and make the car run like crap.

 

My wagon lost almost all power around 2 years ago. At idle it would get very close to just dying out. We had the EGR valve changed and since then it has run pretty smooth (power-wise).

 

^^ there's no EGR valve on our cars from 86-89

 

You know what....I don't believe I ever replaced the O ring when I swapped it out before...It looked okay so I left it (IIRC). Maybe that's a possibility here?

 

I always replace it, they look good but feel hard compared to a new one.

 

Have u checked if ur pre cats or ur cat are clogged? That would cause ur symptons.

 

Precats are hollow...Main cat is brand new. Forgot to add that one in the list. Edited.

 

I wander if you have a grounding problem with your engine wiring harness? Wonder if your sensors are putting out the right info but ur computer is getting a wrong reading. Just a brain storm.

Also I read in a post that if your fuel pump check valve is bad it could mess with your idle??
Got the same problem you got so following along except I got no time

 

Have you ever considered advancing or retarding the cam to set a slightly different timing. It kinda sounds like an old Chevy 327 with .202 heads. At idle they were a bit rough and sloppy but when you cracked it the timing was dead on and it would just leap into the power. Maybe over time your cam has worn a bit and it is effecting its timing at idle. Just a thought from the old school thinking.

 

Not to be flippant at all, but you got that advice way back;do your analysis repairs one step at a time. When you do a lot of repairs at once (shotgun approach), you never will know for sure what the 'fix' was. That's why there always seems to be so much conflicting advice on these boards. Someone may 'fix' the original problem by throwing in new/used parts, but they can only theorize what really worked, because they didn't do it one step at a time-cause and effect.

It could be something as simple as that O ring....but you won't know unless you replace just the O ring. If that didn't work, then you move to the fuel distributor etc. Time whoring, yes. Positive conclusions, yes.

Kevin

 

Gotcha. That's going to be my approach from now onwards. I've come a long way since the beginning though as I have had zero mechanical experience whatsoever...

--

Filled up today. 12.1mpg

--

Tomorrow gonna grab a couple O-rings and swap the distributor back to my original one (I currently have one from the junkyard I swapped in about a year ago).

 

I think you followed a fairly logical path and you documented it better than most. We have to make assumptions based on used or non-dealer parts, available information (not factory service manuals), no factory training, no factory tools, and above all within a budget to avoid or unable to afford the dealer rates. There many unknowns for the 2nd, 3rd, maybe more owners. Sure there are basic repair methods but I can't tell you how many mistakes professional mechanics made where I needed to return the car and still pay for their extra work.

 

Ok I was doing some thinking today...and I read that the vacuum gauge on the instrument cluster attaches to the intake manifold to read the pressure inside.

With that in mind, if my vacuum gauge fluctuates slightly, doesn't that mean that there is not an even, constant amount of air entering the intake manifold at idle?

Does that mean a vacuum leak, or would the airflow plate be moving slightly based on electronic signals from elsewhere? What are your thoughts on this?
I have gone through every single hose on that engine...All the idle air hoses, all the ones that attach to the intake manifold and the one under the KE mixture unit.

EDIT: Is there a way to test the air pressure in the intake manifold with a gauge? Is there a spec I can check it against?

 

Here is a video showing my economy gauge

http://www.youtube.com/watch?v=kMAVAjyVSTE

 

A quick Google search indicates that this is probably faulty air/fuel ratio.