vacuum leak update

[just-n-time]

just-n-time here,I got into the fuel tank filter today,it looked good,some trash but just enough to say it is doing its job.(see pic)
Intake is another story,it is a mess,the air duct housing was not properly seated to the intake must have leaked.
Varnish is abundant in the air duct,and nasty looking in the lower intake too.
I will keep every one informed as I go thru the system j-n-t

[gmercoleza]

Dude, you must be really bored...

Great job. I hope to never have to do that.

[just-n-time]

Originally Posted by gmercoleza

Dude, you must be really bored...

Great job. I hope to never have to do that.

Not even in the least! I just like things to work,If I cant go out and turn the key and go then I must know the reason why.Perhaps It will be for my own edification,or some thing to pass along.Besides I have to do something in my early retirement,j-n-t

[xvvvz]

Ok, I am going to admit my ignorance in the interest of learning something So those pictures are of the ducting from the airbox to the throttle body and they are coated in oil because there was a vaccum leak in the ducting that killed the vacuum which allowed oil from the EGR or something to enter back into the system due to a lack of vacuum? If true, did it kill your MAF? What model of car is this, please?

Thanks!

[just-n-time]

Originally Posted by xvvvz

Ok, I am going to admit my ignorance in the interest of learning something So those pictures are of the ducting from the airbox to the throttle body and they are coated in oil because there was a vaccum leak in the ducting that killed the vacuum which allowed oil from the EGR or something to enter back into the system due to a lack of vacuum? If true, did it kill your MAF? What model of car is this, please?

Thanks!

First this is a 1990 420sel,The trash you are looking at is varnish,and soot from a very rich condition.I split the intake today and have more pics for all to see. The first shows soot,The second is badly varnished,third is cleaned The last is another view of the soot. all the o-rings are hard

[just-n-time]

Originally Posted by just-n-time

First this is a 1990 420sel,The trash you are looking at is varnish,and soot from a very rich condition.I split the intake today and have more pics for all to see. The first shows soot,The second is badly varnished,third is cleaned The last is another view of the soot. all the o-rings are hard

By the way I realize you haven't read the other sights in my name so just in case others have the same problem,I should say this car sat for a very long period and varnish got to it,It was repaired but only skimmed over and so much else needed to be also addressed,sense I got the car I have tried to put it back in the shape it should be in,j-n-t

[just-n-time]

Ok gang, I have completed the task of repairing the vacuum leaks and replaced the wiring(plugs).
Was having an Issue with cold start, It would fire up and search for balance and stall.I fattened up the fuel in small increments Until it held the idle. Cold idle on start up is 1000 rpm then balances to 700 rpm.holds that threw out the warm up and warmed condition.
Test drive I had a slight hesitation on acceleration, I added a little more fuel and it cured the problem.
Now we are looking at a stall problem, after it is warm and has gone quite a long time it acts like(if it had a carburetor the choke slams shut) it starved for fuel or was in a flood condition,like it is choking the vacuum gauge goes to the max. Any more thoughts?

[garymand]

Cool job JNT, Nice engin to work on right? Not an old hand like Dave on these, only took apart one 380. I think the varnish would not be there if the air leak hadn't been there. How did you get it down to 700? hows your timing?

[just-n-time]

Originally Posted by garymand

Cool job JNT, Nice engin to work on right? Not an old hand like Dave on these, only took apart one 380. I think the varnish would not be there if the air leak hadn't been there. How did you get it down to 700? hows your timing?

I have no idea how it got to the 700 I guess the idle control valve took care of that though I did have all the linkage off and started FROM DEAD CLOSED TO just off the stop and brought all the other linkage to meet that position,As I said when I first put the system together the only rpm it knew was 4000.
Varnish is something else though I am sure it had a lot to do with wild adjustments in the linkage and the air leek (vacuum) j-n-t

[garymand]

Tomorrow I'll check the icv voltage for you. Put a timing lite on it and tell us what you see at 700. Then pull the vacuum hose on the EZL and see where the timing goes. I've ignorently played with the mix on my old 380, with my 560 it makes more sense to me now, but it sounds like your mix is about right. What voltage do you get at pin 3 on the X11 round diagnostic port? Mine is about .4VAC I think typically .4 to .6.

By the way "starved for fuel" is not enough gas - plenty of air, and "choking" is plenty of gas - no air, opposites. Pulling the plug on the icv opens the air passage, mine raced so I knew it was too rich. Fun stuff, I lov these cars.

[just-n-time]

Originally Posted by garymand

Tomorrow I'll check the icv voltage for you. Put a timing lite on it and tell us what you see at 700. Then pull the vacuum hose on the EZL and see where the timing goes. I've ignorently played with the mix on my old 380, with my 560 it makes more sense to me now, but it sounds like your mix is about right. What voltage do you get at pin 3 on the X11 round diagnostic port? Mine is about .4VAC I think typically .4 to .6.

By the way "starved for fuel" is not enough gas - plenty of air, and "choking" is plenty of gas - no air, opposites. Pulling the plug on the icv opens the air passage, mine raced so I knew it was too rich. Fun stuff, I lov these cars.

Yes I was quite confused by it all, seems as though I do that to myself when I am not perfectly sure what is happening. The fuel problem was not completely clear to me,one moment it seemed as though it was starving and the next flooded.

[just-n-time]

Garymand, the timing after warmed was at 12* after vacuum unplugged it fell to 5*
Pin 3 reading was 4 to 5 pulsing as the ox or the Eng. was looking for balance still not sure how to fully explain the problem, though today it ran at a rougher idle than yesterday.j-n-t

[garymand]

Sorry for all this detail, but it is a complicated system. I stopped at 11 points til you catch up.

1)I think you are saying the throttle valve is a little open. You said: "I did have all the linkage off and started FROM DEAD CLOSED TO just off the stop and brought all the other linkage to meet that position," and "when I first put the system together the only rpm it knew was 4000."

1)It should be DEAD CLOSED. Its not a carborator. The computer controls all the air at idle. And, the 4000 happened once you fixed all the vacuum leaks because someone used the throttle to compensate for the leaks. I can'r explain how it does that. But now you should have the dash vacuum gauge pegged on economy. Really good vacuum. The engine had a lot of air coming in and good vacuum and that pulled the gas plate down raising the engine speed beyond where the idle system could control it.

The screw on the throttle butterfly is there only to prevent the butterfly from sticking into the aluminum throat. It should be totally closed and even bit just a little. Benz fuel injection has always been that way.

2)ALL the idle air needs to be controlled by the icv. Except for the little bit coming through the bypass tube in the rubber fittings at the input and output of the icv.

3)When you adjust the mix too lean with the allen screw, the vacuum will pull the big air plate down a little and you will hear the sound of air flow increasing past the plate. You should try find that point with the allen screw and back off from there to 700 to 750rpm, air is not noticably coming through the plate, smooth idle, no hunting.

4)Remember that the O2 sensor output changes with exhaust temp and sitting at idle and playing with the mix allows the exhaust to be cooler than real driving. In fact when cold starting (with the sensor cold) the computer opens the icv to give an idle of about 1000rpm, (everything else set about right) until the signal gets into range from the O2.

5) To find the not-too-lean point, turn the allen screw CCW 1/8 turn at a time until you find it. You have to wait for the O2 sensor/computer to catch up and stabalize with the engine. Idle should stabalize in just a few seconds. I think it gets worse taking longer, as you get too lean leading to hunting. Once hunting lean, go back 1/8 at a time, waiting for the computer to stablize. Until you get 700 to 750, air is not noticably coming through the plate and no servoing.

It sounds like you know how to do this and are very close if not too lean already. Check it, drive it, heat it up, stop and put it neutral or park, if it hunts, pull over and quickly try 1/8 turns CW.

6) I can't tell you how rich to go. You want to be far enough away from hunting lean enough to save fuel and have good emissions. Hopefully someone else here has experience of where to leave it before you check the emissions. The mix adjustment will repeat well (the allen will be in the same position each time) and all within only one turn of the allen: go too rich, the idle goes above 800, too low and the idle drops to 600.

7) 600 seems to be a computer limit, once there the hunting gets worse, but rpms won't go lower. I think this adjustment should be set so the idle is about 700 to 750, air is not noticably coming through the plate and no servoing. When you get too lean with the allen, go back 1/8 at a time until the idle is stable: no stumbling sound in the exhaust, no sound of harsh sucking through the air plate, rpm 700 to 750.

8)The hunting is due to the O2 sensor and computer changing the air too far and then changing it the other way too far. The system tries to self-adjust (hunts) to try to keep the engine from stalling or idleing too high. I'm not sure, but I don't think the gas is servoed at idle. I think its just the air flow through icv that is under computer control. The icv is big enough to control all the idle air the engine needs.

Its normal for the O2 system to look around a little for the best setting and older engines never have a perfect best setting, the .4 volts at pin 3 X11, will move around +-.05V as the O2 sensor roams around making sure its keeping the air about right for the gas flow.

9) The .4 volts moves around as the O2 sensor/computer adjusts the fuel ratio with the icv. The voltage at the icv is the result, adjusting the air in this 'closed loop' idle system. The input is the O2 sensor.

10) My vacuum at the EZL does the same as yours. There is a "dongle, (computer term)" R16. Its a plastic plug connector with no wires coming out of it back next to the brake booster. It controls the 5* setting with vac off. The normal value of R16 is 750 ohms.

11)I'm unclear what the vac-off timing should be, I don't have the manual for this car. But vac-on timing has to do with idle speed, mine was up at 30* with 950 rpm idle and 12* at 700 rpm.

[just-n-time]

Originally Posted by garymand

Sorry for all this detail, but it is a complicated system. I stopped at 11 points til you catch up.

1)I think you are saying the throttle valve is a little open. You said: "I did have all the linkage off and started FROM DEAD CLOSED TO just off the stop and brought all the other linkage to meet that position," and "when I first put the system together the only rpm it knew was 4000."

1)It should be DEAD CLOSED. Its not a carborator. The computer controls all the air at idle. And, the 4000 happened once you fixed all the vacuum leaks because someone used the throttle to compensate for the leaks. I can'r explain how it does that. But now you should have the dash vacuum gauge pegged on economy. Really good vacuum. The engine had a lot of air coming in and good vacuum and that pulled the gas plate down raising the engine speed beyond where the idle system could control it.

The screw on the throttle butterfly is there only to prevent the butterfly from sticking into the aluminum throat. It should be totally closed and even bit just a little. Benz fuel injection has always been that way.

2)ALL the idle air needs to be controlled by the icv. Except for the little bit coming through the bypass tube in the rubber fittings at the input and output of the icv.

3)When you adjust the mix too lean with the allen screw, the vacuum will pull the big air plate down a little and you will hear the sound of air flow increasing past the plate. You should try find that point with the allen screw and back off from there to 700 to 750rpm, air is not noticably coming through the plate, smooth idle, no hunting.

4)Remember that the O2 sensor output changes with exhaust temp and sitting at idle and playing with the mix allows the exhaust to be cooler than real driving. In fact when cold starting (with the sensor cold) the computer opens the icv to give an idle of about 1000rpm, (everything else set about right) until the signal gets into range from the O2.

5) To find the not-too-lean point, turn the allen screw CCW 1/8 turn at a time until you find it. You have to wait for the O2 sensor/computer to catch up and stabalize with the engine. Idle should stabalize in just a few seconds. I think it gets worse taking longer, as you get too lean leading to hunting. Once hunting lean, go back 1/8 at a time, waiting for the computer to stablize. Until you get 700 to 750, air is not noticably coming through the plate and no servoing.

It sounds like you know how to do this and are very close if not too lean already. Check it, drive it, heat it up, stop and put it neutral or park, if it hunts, pull over and quickly try 1/8 turns CW.

6) I can't tell you how rich to go. You want to be far enough away from hunting lean enough to save fuel and have good emissions. Hopefully someone else here has experience of where to leave it before you check the emissions. The mix adjustment will repeat well (the allen will be in the same position each time) and all within only one turn of the allen: go too rich, the idle goes above 800, too low and the idle drops to 600.

7) 600 seems to be a computer limit, once there the hunting gets worse, but rpms won't go lower. I think this adjustment should be set so the idle is about 700 to 750, air is not noticably coming through the plate and no servoing. When you get too lean with the allen, go back 1/8 at a time until the idle is stable: no stumbling sound in the exhaust, no sound of harsh sucking through the air plate, rpm 700 to 750.

8)The hunting is due to the O2 sensor and computer changing the air too far and then changing it the other way too far. The system tries to self-adjust (hunts) to try to keep the engine from stalling or idleing too high. I'm not sure, but I don't think the gas is servoed at idle. I think its just the air flow through icv that is under computer control. The icv is big enough to control all the idle air the engine needs.

Its normal for the O2 system to look around a little for the best setting and older engines never have a perfect best setting, the .4 volts at pin 3 X11, will move around +-.05V as the O2 sensor roams around making sure its keeping the air about right for the gas flow.

9) The .4 volts moves around as the O2 sensor/computer adjusts the fuel ratio with the icv. The voltage at the icv is the result, adjusting the air in this 'closed loop' idle system. The input is the O2 sensor.

10) My vacuum at the EZL does the same as yours. There is a "dongle, (computer term)" R16. Its a plastic plug connector with no wires coming out of it back next to the brake booster. It controls the 5* setting with vac off. The normal value of R16 is 750 ohms.

11)I'm unclear what the vac-off timing should be, I don't have the manual for this car. But vac-on timing has to do with idle speed, mine was up at 30* with 950 rpm idle and 12* at 700 rpm.

Garymand,first yes,the lower plate I set just off the stop I thought I read some place that it was to be set at 1000 thnd mm off bottom ofcourse that may be what it should be at the stop too.
Carb type intake leeks or cracks you can over compensate by increasing the idle mix this must have bean what they attempted to do with th linkage,because when I dropped the links off the balls I was able to get off the screaming 4000rpm to a 750 or 800,then I pulled the plate off stop.So what you are saying is get back in and reset the plate to its stop and readjust more in the fuel till I find that place where it dose not hunt!

[just-n-time]

OK, I went out to the shop and took another look at things and reset the throttle body to its stop position, then began to lean out till I could here that rush of air over the horn, at that point I added fuel in 1/8th turns till it began to smooth and finely it stopped searching.Now if it will stay things are going in the correct direction! Yes I know I am a nut to put so much time into the car but it is such a fine car I hate to see it go all to h--l.