ps2cho

Where is that connector located? Is it under the front passenger footwell? I thought that plug was for the alarm.

White_Knuckles

I think that is it, under the passenger floor carpet. Not sure on an 88 though.

Yacht Master

You should be able to see it comming through the floor board

YNVDIZW124

You should not have adjusted the EHA Valve at all. I adjusted mine to make it a little lean but i made sure all my other electronics where in working order. The EHA valve does have two O-Rings on the fuel distributor side. If your car has problems starting replace the Temp sensor ( two post) at the rear of the engine. The OVP relay only powers the cold start injector but the temp sensor controls the idle and EHA valve. Also you may need to replace your throttle postion sensor if you have an idle that goes up and down randomly. I would outline it with some type of paint where the original one is because when installing it you have to have it in the exact same position as the original.

I suggest you try to fix one thing at a time instead of messing with everything at the same time. Mercedes and the w124 have a sequence of thing you need to do before being fixed when it comes to the fuel system. I would start changing major parts like the O2 sensor and the fuel distributor before you do any adjustments on the fuel system.

ps2cho

Well there was no harm in testing it...I just read on other posts that it was a possible problem...so just giving it a quick turn with the possibility of finding the problem was worth it. I put it back to where it originally was because it seemed to have a little hesitation accelerating, but now its back to where it was.
I have been working all weeked straight so finally tomorrow I can get down and disconnect that O2 sensor.

And no the car doesn't have problems starting. Sometimes if its real cold it takes many cranks before the engine starts. Generally its 2-3 seconds holding it before it starts up...It's not right away...but I expect that to be so with an older car.

White_Knuckles

Ps2,

I've tracked your car across 3 sites and see no report on your fuel filter condition. Have you determined it's clean or did you remove it and find evidence of deposits? How does it run with the O2 out of circuit?

The guy recommending the fuel distributor used the term "crap shoot". He's right, and a proper disclaimer. The car has a troubled history as you've described. Think of what part(s) dates back to the prior owners woes. Things like the fuel distributor fall in that range but is a guess.

Before ordering a spendy part, you need to recheck the basic stuff. Actual vacuum tests with a gauge. Squirting cans of various products is a handy method but leaks hide. Fuel pressure readings would be of value.

The O2 sensor is suspicious from contamination. How much SeaFoam, Tecroline and other VooDoo chemicals has she downed? Is the EGR valve stuck open? There still are some easy but critical tests.

ps2cho

We replaced the fuel filter when we first got the car and there was no "noticeable" solids...We weren't looking for any, but I'm sure that we would have noticed if there were solids in it from taking it out.

I'm pretty sure we have done vaccuum tests...but I need to double check with my dad.

I looked under that front passenger seat and there were 3 connector (one of them was for the alarm as it goes into the becker unit) and so I didn't know which one was the O2 sensor, so I just unplugged each one seperately.
One was black and one was Red. The red one made no difference, but when the black one was pulled, the car started up and revved to about 1500 rpm before settling down. Both were still misfiring.

As for the seafoam, we put the worth can through it.

YNVDIZW124

you should just replace the fuel distributor and be done with it...

ps2cho

Hey man I am listening to you and taking your advice...but I have close to no experience with cars at all so I'm just doing what I can test because I don't know how to take out fuel filters and stuff. Half the stuff posted on here I have never even heard of for example EGR Valve (still no clue what that is or where its located or how to check if the valve is open).

I want to follow your steps to make sure I am doing it the right way, but I can't do it alone and my dad doesn't have much time to help me.

I can't afford to just attack it blindly then end up with my car out of action because I have school and work.

I'm learning alot from this, but I'm still too uncomfortable to tearing parts out of my car when I don't "really" know what I'm doing. Sure I can follow my haynes manual but things aren't always as easy as they look.

ps2cho

Ok I'm trying to do that vacuum leak test but I'm having some problems...I'm not getting any readings from my multimeter...

I found this guide which made it easy for me to understand:
http://www.mercedesshop.com/Wikka/M103VacuumLeak

But my multimeter isn't reading anything at all. I have it set on volts and I have followed every step in the guide. I don't understand...

I have the (+) attached to the plug which the green wire went into...and the black is grounded...

What am I doing wrong?

YNVDIZW124

That could be the problem but i don't think it would make it misfire like that. If the O2 sensor is not reading or even working your fuel injection system is going to run in limp home mode. I would change it asap since it's only $50

http://www.autozone.com/R,APP233993/...ductDetail.htm

If i had one i would use a stethoscope and listen to the top of the fuel distributor but since i don't a long screw driver does the job.

White_Knuckles

Are you sure the volt meter settings are on DC? Measure across the battery or some known DC source to test your meter. It looks connected properly and hopefully you have a good ground. The sensor should have some sort of output. You would have check engine lights if it was completely toast.

The EGR (exhaust gas recirculation) is a valve located on the exhaust manifold that is vacuum operated. The buggers are known to stick or never open. Stuck closed not to worry, stuck open - rough idle.

Your car may not have one, can someone verify this?

YNVDIZW124

no I don't think he has one, only 90 and up came with it i think but i'm not sure.

shadowgriffen

Correct, mine does not have one and I have seen them on 90+cars.

squablow

This is probably a dumb question, and you may have covered it already, but you are using 93 octane fuel, correct?

YNVDIZW124

I've put 103 octane from vp racing fuels and it's way way nicer in acceleration and take off. I put it in the same day before my smog check and it passed smog with flying colors.

ps2cho

Yeh the meter works fine...I had it grounded correctly (tried different places just to make sure). Also....I wasn't getting a check engine light at all even when it was unplugged.

So you are saying I should replace it as it is more than likely ruined due to the contamination, but it will unlikely solve my problem. Correct?
I was going to replace it regardless because I am sure it is ruined, but I didn't know as to when would be the best time to replace it.

Yes of course I don't believe even with the wrong octane fuel, it would misfire. It would just "ping" when accelerating and be very unresponsive and unhappy.

----
The following IS NOT HAPPENING NOW
Just needed to say that before it gets misconstrued....but thought I'd share this with you guys:

One day I was driving and it was misfiring SO horribly that it wouldnt accelerate even with the kickdown pressed....I pulled over to figure out what the hell was going on and look what I found...



After I let it cool for 15mins....it was fine and I drove home without any more problems....Am I correct in saying the oil got into the precat and just became a huge oven in it? Could this have any effect on anything precat to the end of the exhaust? I know it's not causing the misfire...but I just wanted to check nothing downstream could be affected that would be significant to check at some point when I get the misfires fixed? I should probably concentrate on one problem at a time...but I liked the pretty picture

Thanks guys.

ps2cho

Oh and and my 88 does have an EGR Valve!

http://catalog.worldpac.com/mercedes...part=EGR+Valve

It shows it is available.

YNVDIZW124

Nope, You don't have one.. this is your engine right?...

ps2cho

Yes that is.

Then why do they have one available to buy for the 88 300TE? Weird...

ps2cho

Ok just figured out the Vacuum Leak test. The article states the negative was to be grounded, but it was supposed to go to the other end of the O2 sensor, otherwise the Sensor was not being read.

Car is great. No leaks at all including Injector Seals. O2 sensor is good (I will replace though as it has to be damaged due to oil) as it was reading everything so its not the O2 sensor.

ps2cho

Ok guys so the next step would be to check the Fuel Pressure Regulator, then replace the Fuel Distributor right?

As for the exhaust back pressure: This is fine because the car accelerates without ANY hesitation and is smooth all the way up to the red line. The problem only exists at idle and low rpms. It's absolutely beautiful to drive and nobody would ever know anything is wrong....when its moving. As soon as you pull up to the stop light it just misses and misses shaking the car constantly. So there is no way the cat is blocked to any extent otherwise I would have having acceleration problems, but there isn't even a hint at all at any rpm's.

Now, as for the fuel pressure regulator, can I check the regulator itself using a multimeter or am I just checking the pressure using a gauge? I have scanned google and other forums for several hours but couldn't find any information on how to do this.

White_Knuckles

Glad you have the O2 tested with output. Strange the check engine lamp remained off. Is the pic showing a hot spot or flamage? The purple areas are hard to define.

I've seen many part listings for items your car doesn't use. Always double check part numbers at a couple sites.

You comment the O2 is probably hosed from "oil". Is this related to known contamination? The cat or pre-cat can't be assumed fine if it was cooking. That seems a little scary and what healed it? You may have flow blockage that you can't hear or feel. How much oil or other chemistry has been through the system?

Can't assist with your fuel questions just wondering if you need to roll with a small CO2 extinguisher with you?

ps2cho

You see I would believe that the cat/precat has been damaged, but the fact that the car has no problems other than at idle makes me assume there are no blockages. If there were any type of blockage, then the car would have problems other than at idle...but it doesn't...

The O2 being hosed is because of the oil consumption through the worn valve stem seals (I was using a quart of oil every 500 miles). The O2 sensor was reading ok though so I believe it is fine....but at some point I will change it because it must be tarnished in some way or another whether the damage will be seen now or in 10k miles.

There are a couple items on ebay right now such as the fuel distributor, fuel pressure regulator + eha valve for $10 and so far there are no bids. I am going to see if I get all 3 for a reasonable price. It ends tomorrow so hopefully I can get them cheap and then that would be easy to replace/test.

Yacht Master

Did you get 9 volts out of the O2 sensor?

You have ruled out vacuum leaks in the past, but you need to revisit that and make sure the leak is not at the end user ( brake booster-vacuum reservoir, Air conditioning controls, fuel tank evaporative system)
From what you have stated it sounds like text book vacuum leak.