whats wrong with my 500 engine?

[nathan]

by the power of youtube, please help me!
http://www.youtube.com/watch?v=eiwKaI5Y1eE
although this is a donor vehicle and the engine and trans will be rebuilt, id like to know if anyone knows WTF is going on with my 500.
after a brief acceleration, if i let the rpms drop to ~ 1500 and then hold the accelerator pressure, this bizarre knocking occurs...its audible and you can feel it in the car...it will stay as long as you keep your accelerator at that position...if you accelerate or remove your foot off the pedal, it goes away?!  it does it in 2nd and 3rd noted, not so easy to get it in 4th so i dont think its a tranny issue...in general, this car is not putting out its appropriate power except for a very narrow area when the acceleration finally kicks in, whether thats related i dont know?
does anyone have any ideas??
many thanks
nathan

[TJ 450]

Sounds like it hasn't got any better  .
I've been searching around for some diagrams of the KE-Jetronic system. There doesn't seem to be a lot of info, however there is a throttle switch under there somewhere according to one diagram I've seen. That sensor on the cold air intake is still a mystery to me too. I'll continue my search for KE-Jet info.

Tim

[Big_Richard]

.

[WGB]

Nathan,

I have a copy of the M-B WIS (Workshop Information System) which is pretty comprehensive for 126's.

Give me your VIN and engine Number plus year of manufacture and in a spare moment(or next few days)  I'll start wading through it.

It sounds like weak mixture with detonation or a wandering spark advance if you are sure it isn't in the transmission.

The KE Jetronic is really only K Jetronic with some electronic control of richnmess and idle control (In later models)

I also have the software and cables for electronic diagnosis but do not know if they are applicable to your car and I would be trying them for the first time - so if you're game......

I am quite happy to come for a drive over at some stage of the weekend but have a grand-daughter's birthday at lunch-time Sunday.

Bill

[nathan]

you are a champ Bill,
id love to see this computer diagnosis stuff in action, but i think rather than you shelling out 200 bucks to drive to my joint, it should be the other way around and maybe i come up to yours when you are free!
if you get time, the 500s VIN is WDB1260372A423878
thanks again
nathan

[WGB]

I'll go through the WIS and see if there is a diagnostic chart of any kind tonight or tomorrow and let you know.

I would put a timing light on the motor and just have a rough check of timing stability at idle and at different revs.

Check all vacuum lines are connected and correctly for advance and retard.

The other way that noise could  be made is a shorting H-T lead on resonant back ground eg aircleaner.

Just look at the motor in the dark and see if there are any blue sparks anywhere.

Bill

[WGB]

Just another thought - is it engine revs or road speed.

If it is road speed I would think about your front flexible driveshaft coupling. That would be exagerated in the lower gears due to the extra torque but I would expect it would be speed related.

I used to shred my 300SE one every 50, 000 km or so so a hard driven 500SE would be even harder on it.

If it is that it is not safe to drive.

Bill

[nathan]

it only seems at this rpm bill, the car does knock with the noisein the vid...its hard to tell where the noise is coming from...if it were a flex disc i wouldnt have thought the rpm counter would pulse though?  the speedometer remains constant and doesnt seem to move?
thanks for the differential, ill still look at the disc anyhow!

[TJ 450]

It seemed to occur after backing off and under very light throttle.
IMHO the noise was in the driveline, as the engine was cutting in and out. The lack of power appeared to be due to the mixture leaning out/ignition timing issues. I think you should change the fuel filter and check the ignition timing as well. In any case, I wouldn't be doing any spirited driving until the problem is fixed just in case something breaks.
It sounds like you've got the resources, Bill. There doesn't seem to be much info on the net (well at least I haven't found it yet).

Tim

[13B]

Does your car have an air-pump for the pollution control system, or EGR system etc. ?  I've seen cars fitted with the afterburner type (air pump) pollution system give this problem when packing up.  In fact my 6.9 still has the pump in place but no drive belt, and I have no desire to add one... I've driven rotary engine vehicles with failing pollution control systems... if the air pump doesn't get you, the PCV valve does, if the PCV valve doesn't then the decel control valve (aka gulp valve) does.

1st thing would be to disconnect the air pump hose and block all the emissions hoses off to make a 'dirty' engine and see if it runs right, then unblock each subsystem and retest. 

I.

[TJ 450]

I'm fairly certain the only pollution control was EGR, being a UK car.

Tim

[WGB]

Hi Nathan,

I have all the data you will ever need on the 500 KE Jet system and ignition.

I also put your VIN into the Russian Database - it's a very well specced 500 with slippery diff and most of the fruit - ooh rear footrests even.

I was just making sure that ASD wasn't specified as this was an early version of traction control and could have been a source of problems.

The Russian Database gives the VIN/engine no/Transmission no and this is the same given in the WIS.

I have printed out the scematics for the KE jet system with and without cats, check sheet for the EGR (There were two versions and you should have the later version), and the computer is slowly printing out a lot of pages on KE jet diagnostics.

I will PDF these and e-mail them to you when I can.

There are several sections on KE jet diagnostics but I have only concerned myself with the general running characteristics as that runs to 52 "WIS" pages( 18 printed A4 pages).

We can get anything else if needed - you are unfortunately 1 year too early for fault code storage and retrieval which started in 1989.

Bill

[nathan]

Bill,
if you didnt have such a big mo, i could kiss you