'88 300TE SSS ideas?
 

I have searched and read all I can see.

1988 300TE with 64,000 miles.
A/C not working.

Starts fine, runs fine until 85deg is showing, and then begins irratic misfire that shakes the whole car. Not constant, sometimes 3 secs betweeen misses and sometimes 10 secs.
The car is also alway very sluggish at low rpm.
Normal idle speed is showing 750/800rpm. When the miss happens, that idle drops by 100/200 rpm. Economy gauge normally reads halfway between the stop and the start of the red section.
It has stalled once in this condition but started again instantly.

Yesterday it did something different.
First thing was that the battery was dead. I think it was the alarm. I charged it for a while, disconnected the alarm under the carpet and it started instantly.

When I drove it, I noticed the miss was a little harsher, I was sitting waiting for my son, and I watched as over a few mins the idle speed crept up to 1000rpm...I noticed that the economy gauge was pinned to the left stop... ie max vac..... then "boom" the engine just quit.
No miss and stall, it was lights out, like I had turned off the key!
I restarted it and it fired instantly.
The idle resumed at 1000rpm and after a min or so it repeated the same thing.
It restarted instantly again.
Just after the 3 time it did this my son arrived and we drove away.
The miss and stumble was all the way up the rev range and continued all the way home.

I knew that the car had an issue like this, but am pretty handy, so was not put off.
I do know that I may have a vac leak as there appears to be a pipe missing from the valve cover to air filter housing pipe.
The OVR has not been replaced according to the bills I have, but the fuel injectors have, as has the potentiometer, ignition leads, cap and rotor.
The car sat for 12 years or so from 1990 to 2002, and failed its first smog badly.
Its most recent smog it only just passed.... HC was on the max at 105 and 81PPM. The PO said it was missing when it was tested.
I listened to the fuel pump/pumps and they sound a little odd to my ear. Kinda "gritty", not like I know Bosch pumps normally sound, but if there are two, maybe its me.

So, I know this is common, but with so much info, where should I start?
OVR?
Idle control?
Ignition system?
Vac system?
Fuel filters/pumps/relay?
Mixture?

I guess I need some help with the priorities to figure this out?

You need to see if the O2 sensor is working & if the Lamda (duty cycle) is adjusted properly...

OF course the engine should have a GOOD secondary ignition tune-up OR scopped to make sure that it is in good order...coil output is very important on a HOT CIS engine.

Replace the cap, rotor, wires with good brand, not Bosh, and most important, replace the distributor cap o-ring seal. Sound like you have bad ignition to me.

Thanks for the responses.
The secondary ignition system looks like it was done, but I will look at the bills tonight and see what make they were.
The O2 senser was replaced recently... I assume cos I see a bill for the part!

I agree that it sounds like an ignition issue because of the suddeness of the stall.
I am new to MB, but have a quite a lot of mechanical experience, so what tools will I need to check the duty cycle? I have a good analog multimeter, but love tools, and always prefer to buy and invest in stuff that pays back over time!
Or would it be better/cost effective to just take it to my local Indie?
It seems from a lot of the posts that this issue is difficult, expensive and hit and miss even using the Indie!

Should I order a new OVP?

I took off the airfilter and looked all around, could not see any loose connectors or vac cables. Looked at all the vac lines and the vac tube to the IAC, all looked ok.
Here is a pic.
http://img.photobucket.com/albums/v2...obmerc012E.jpg

I pulled the cable from the IAC and the revs went up from 750ish to 1000...
When I pushed the connector back on the engine stalled straight away... is that normal?

Yes. Thats a good sighn. You need to visably look at the ignition system. Even if the cap was replaced, No one, for some reason, never changes the o=ring that seals the cap from moisture, and then it ruins the new cap.

Merkey:

This weekend I will take pictures of my 300TE engine, from the same perspective so that you can do a comparo.

I will also take a picture form the other side, so you can see whether there are any plumbing differences between the two engines.

In your picture I can't see the thin hose leading up to the big, fat breather hose.

BTW, while you have the air cleaner assembly off, you may want to clean and lube the throtle linkage.

Your engine looks very clean, reflecting its low mileage :D

Thanks GVB and LGB,

GVB:
I have a item on the PO's receipts that is titled "Distributer Cap Gasket". It is the next line item under the distributer cap, so I assume it was done at the same time. Is that what you are talking about?
These items were bought from Importec and have a BOS moniker as Brand, so I assume they were all Bosche.
As the problem was the reason they sold the car and they replaced all these items in trying to find the cure, I will assume for now, that they were NOT the cause and will look elsewhere.

The coil is $140, so should I replace it, or is there a way to test?
The IAC is $300! Ouch!

I was just thinking today that the removal and replacement of the connector from the IAC, replicated the stall condition I saw on monday exactly... ie, a rise in idle speed to 1000 and an instant stall.
Would I be wrong to guess/speculate that if the IAC is faulty or its power was interupted, it would cause the revs to rise, then when it reconnected or self corrected the engine would stall....
Any way to check it?

I am a little confused by the Vac/economy gauge... its very erratic... today it was idling at 750, but the gauge was reading at the start of the red section!

LGB:
I looked all over for the missing pipe... nothing to see.
The engine ran fine without the filter in place, did not misfire that I could see.
Yes, is was very clean in there... I will lube the linkage at the weekend... and clean the engine and bay a little more.... not clean enough for me yet!

The miss was less noticable today at idle, but I could feel it at 1500 rpm as I moved the car into position slowly on my sloped driveway.
The gearbox also seems slow to engage in D, and is a little harsh shifting sometimes.
Could that mean a vac leak somewhere?

This weekend I will look and see where the small tube is in my car. The interesting thing is that from year to year (and even w/in the same production run) Benz makes small changes in the engine plumbing/hardware. So maybe you don't have that small tube. :eek:

The slow-to-engage trany could be due to low trans fluid. It could be a modulator (by now I am out of my league).

The harsh shift could be bad flex disks, bad tranny mounts or a vacuum leak. Do a search here under flex disks.

The erratic "economy gauge" (nothing but a fancy vacuum gauge as you probably already know :D ) is interesting. The one in my 300TE has always been off and erratic. In my 420SEL it was to the left at idle, climbed to the red side under acceleration and then settled back as I cruised along. But the gauge in the 300TE has never been that normal.

Wonder if there is a connection here? :confused:

I have a 1992 300TE that I am working on right now - it's been an interesting experience, this is my first MB gasser in many years....

I'd check the vacuum line that runs from the back of the intake manifold to the transmission, since it sounds like you have vacuum problems and transmission shifting problems.

On my 300TE, I located a small vacuum leak in a vac. line that runs underneath the battery (caused by battery corrosion ignored by the PO).

From the picture, it appears that your throttle plate is set so that it is open a bit too much for idle. On mine, there's about a 0.1mm gap between the sides of the throttle body and the plate. Also, make sure the plate is centered.

Since the economy gauge is also erratic, check the vacuum connection to the instrument cluster.

Thanks Chris.
I will put the car up and look this weekend.

The car battery was flat AGAIN this morning... I charged it and ran it yesterday for 10 miles... I will have to look at this issue deeper first... or maybe its connected! I have already disconnected the alarm wires... that was not it, it seems!:rolleyes:

"slim" breather hose
 

OK Merkey here are some pictures.

The slim hose that seems to be missing in your car goes from the air assembly breather hose then routes under the ICV and then hooks up to another metal valve (or part) close to the ICV.

I hope the first two pictures help.

The third picture is for my education.

What is the name/function of the part circled in red? I disconnected it to clean the terminals. There is a wiring harness going from the part in question that connects to the main wiring harness.

Thanks.

Your pic
 

I marked in your pic where the "slim" hose should go.

Let me know if you find anything.

Thanks LGB!

I had the air filter off ealier today, and I will take it off again in a few mins...
I was just about to post this....
http://img.photobucket.com/albums/v2...a/dad/OVPe.jpg

This is the OVP from his car...
If you hold it and shake it... it rattles....
Did I read somewhere that that is a bad sign?
The tabs at the bottom also look messed with... how does it come apart and what do I look for inside?

Anyone?