disabled EGR, now what? - PeachParts Mercedes-Benz Forum

Grdenko · #1 10-29-2003, 01:54 PM

so i disabled my egr by unplugging the vaccum hose from it and i plugged the end of the hose, and my car seems a little faster, but i could be in my head.

does doing this really completely disable the EGR? is it because the vaccume opens and closes a valve in it? i dont really know how the EGR works i figured it was open all the time.

does this mean that my intake will no longer fill up with nasty black goo? if so, is it worth the effort to clean out my intake manifold and charge air pipe?

i finally located my ALDA, its underneath the intake manifold so i could easily adjust it if i took the manifold off. does this really make the car faster or just suck fuel?

thanks for all your help

gsxr · #2 10-29-2003, 06:32 PM

1- The EGR valve is held closed by a spring. It opens when vacuum pulls against the spring to suck it open. If the valve seat is dirty or damaged, or the spring is weak, it can prevent a proper seal and not keep exhaust gasses (and soot) out of the intake like it should. Plugging the vacuum line will disable a *good* EGR valve - not a bad one. To kill a bad one, you need to install a block-off plate between the valve and intake, or a blank plate to remove it entirely.

2- Your 2.5L Turbo has computer controlled turbo boost. It senses the EGR operation. If you kill the EGR on these motors, power usually drops drastically as the computer "knows" what you did and punishes you for it. Killing the EGR on the 1990-93 300D 2.5L takes more work. One enterprising fellow posted detailed info on this forum a few months back - he made a special circuit board to "fool" the computer into seeing the proper signals. The other alternative is to convert the turbo wastegate from a computer/vacuum operated setup to the old style mechanical/pressure type. "OldSouth" did this on his engine. Both methods work well.

3- You need to clock your car 0-60 with a stopwatch. Factory spec is roughly 11.5-12.0 seconds. If your car is close to that, it's fine. If you are 14+ seconds, you're losing power - could be lack of boost (maybe computer issue), or lack of fuel (IP). Time it first, then let us know what it is.

4- Increasing the ALDA setting will help with off-idle power. If the car is a slug off the line, yes an ALDA adjust should help. If it's good off the line but weak up top, the ALDA probably will NOT help. You don't need to remove the intake. You remove the ALDA, tweak it, and re-install. Photos on the 603 engine are here:

http://www.meimann.com/images/mercedes/OM603_injection/

Here's what I did to remove my EGR (for off-road use only) on a non-computer controlled OM603:

Grdenko · #3 11-01-2003, 04:52 PM

so i timed my car 0-60 with and without the EGR disabled and it was the same time, 15 sec. so i guess my car is running pretty slow.

i posted a thread on this topic a few months ago, how my car seems to have gotten slower over the years and i really have no idea why, so anyhelp with this issue would also be helpful.

but anyway, im sure that it was the egr i disabled, maybe my car is so slow that it wouldnt make a difference.

to be continued...

#4 11-01-2003, 10:37 PM

Must be slow, my poor old TD with the nailing cylinder can do 0-60 in 18. Might be time for a vacuum check-up. The EGR might not have been getting a signal at all in the first place!

Grdenko · #5 11-01-2003, 11:00 PM

how do you do a vaccum check?
is it something i can do myself, is there some tool or gauge to do it with?

thanks

#6 11-01-2003, 11:28 PM

Goto AutoZone and get a MityVac. As I do not have a 2.5, i don't know details about it's vacuum system(s), I'm sure others will chime in for that information. 15 seconds is about the "normal" time for a 617 powered 300D and the more powerful 2.5 300D should be, as gsxr said, in the 12 second area. Power is clearly being taken for some reason if it's that slow before the EGR is disabled.

CJ · #7 11-02-2003, 03:28 PM

I was readng this thread thinking that I have the same boost problem as this other guy. Back in 2000 when I bought my car one of the first things I did was pull the intake and have it hot tanked to clean out all the nasty stuff the EGR had been throwing up in there for the past 10 years. When putting back on the intake I machined a "block-off" plate for the EGR.
Since I just bought the car and it was a dieel I assumed it was supposed to be that slow.

I just removed the plate and took it for a spin...I would not say it was fast, but relatively speaking there is a BIG difference in the boost and acceleration.

Grdenko · #8 11-04-2003, 03:07 PM

looked for a mityvac, couldnt find one, ill try the mega-autozone out in the 'burbs.

anybody know how much one of these costs?

id also like some details on how i can make the computer think the EGR is still enabled. do i really need to do this? whats easier/cheaper, getting a mechanical wastegate or messing with the computer?

thanks

gsxr · #9 11-04-2003, 03:34 PM

Cheap MityVacs are in the $20-$40 range, the "good" ones are in the $50-$100 range. The BEST deal I know of is at TheToolWarehouse.net where they have the top-of-the-line Silverline 4050 kit for only $60. (I paid about $90 for mine - d'oh!!)This is the metal-body, dual-converter pump that creates both pressure AND vacuum - very handy for testing the ALDA and pressure-type wastegates, as well as the overboost switch in the manifold. I also use it to test turbo boost pressure since it has a handy gauge that reads to 30psi! Here's a direct link:

http://www.thetoolwarehouse.net/shop/MIT-4050.html

As to how to disable the computer-controlled EGR, search this forum (archives), there was a thread specifically on this topic, where someone did exactly what you want to do. He used an electronic method, which takes some knowledge of electronics of course. Converting the wastegate to a pressure type will take more muscle and probably cost more in parts, but is simpler. It depends which you're more comfortable with, IMO. Since I don't own a 2.5T, I have never done this myself, so my advice is limited to what I've read others have done! If you can't locate that thread, let me know, I think I saved the link somewhere - I'll attempt to dig it up if needed.

HTH,

Grdenko · #10 11-06-2003, 03:53 AM

ok, so last night i took a real good look at my engine, just stared it down for like a hour out of frustration. then it occured to me to start taking it apart... uh oh

so i just randomly started taking parts off of the engine (which i have never done before by the way) just to trick myself into thinking i was fixing something.

i started with the charge air pipe, and after seeing how nasty it was in there, i decided to take the EGR off, and it progressed from there.

when i got the EGR off, i could really see how nasty it was. both ends were completely blocked off, with soot on the exhaust side and sludge on the turbo side. i figure this could be the root of my problem, if the egr is clogged shut, it is disabled and the computer would cut out the turbo.

so i cleaned it real' good with wd-40 and put it back on the engine, but not before taking the valve cover off and staring at that for a while (it was so clean in there!)

then i got the car out on the road to time it, no good, still 0-60 in 15 sec. yeah, big disappointment, but it was a shot in the dark, but at least i have the satisfaction of knowing the EGR is clean.

but the saga doesnt end there...

tonight i decided to go stare at my engine some more, but this time it didnt take me very long to notice something. a vacuum line at the very front of the engine cover was disconnected.

i had seen this disconnected line before but never thought much of it because the other end it looks like it should go into was plugged with what looked like a factory plug, so i figured it was a spare line or a test point or something. but tonight, i decided to consult the service manuals to see if it should be connected. this move will certainly alter the course of my life forever.

upon finding the vacuum line i was looking for in the vacuum circuit diagram of my engine, not only did i learn that this line was in fact supposed to be connected, but also what its purpose is.

this vacuum line, the very same one i had ignore and passed off as a 'spare' for all of these years, was, according to the diagram, the one and the only line that supplies vacuum to the EGR, the turbo, the wastegate, AND the transmission.

OMG

so, just plugging in this little tube will fix all of the problems i have with my engine? the slow start-ups? the late shifting? no way, cant be that easy, not possible, not that little tube, no, this is stupid, cant expect much. guess ill try it anyway

i noticed the difference immediately. the moment i put it in gear a shiver ran down my spine, i couldnt believe it, so i got the stopwatch.

0-60 in 11 seconds flat,
while laying down a soul patch of rubber going into second gear at the same time

its like a new car, i dont even recognize it, this is outrageous

as for how it got disconnected and plugged to begin with, ill have to investigate that at a later date, have a little chat with my mechanic. but for now, im just going to enjoy my new car, which i never would have had without the help of my service manual and the people on this forum.

word to your mother.

peace out
Andy

R Leo · #11 11-06-2003, 04:16 AM

Another forum success story!

Poo! Benz mechanics, who needs 'em?

TX76513 · #12 11-06-2003, 07:22 AM

Quote:

Originally posted by Grdenko
looked for a mityvac, couldnt find one, ill try the mega-autozone out in the 'burbs.

Go to Harbor Freight -they are currently on sale.

gsxr · #13 11-06-2003, 10:33 AM

AWESOME! Enjoy your "new" car!

Stevo · #14 11-06-2003, 10:58 AM

AWESOME! is right...you know what they say "if you want something done right, do it yourself"

Grdenko · #15 11-06-2003, 11:17 PM

well, after driving around in my 'new' car today, i found out that it has a problem.

whenever the transmission shifts up, there is a loud 'thud' sound and it is shifting very hard. i remember the car would do this back when my brother drove it in high school because it would always make me spill my coffee, just like in Top Gun!

that must have been before the vac line was plugged, because for as long as ive driven it, the transmission has been smooth.

as i said in my previous post, i THOUGHT the line i re-connected supplies vacuum to the tranny, but after i noticed this problem i went back to look at the vac line diagram more closely, and it doesnt, a different line does.

i searched for 'transmission thud' on this forum and found that alot of people have this problem, and the answer is always 'you have a vacuum leak'. well, i didnt have a vacuum leak before i reconnected the vac line, so the leak must be in the sections of vac lines i re-connected. if i turn the engine off while i have the hood is open, i can hear a slight hiss coming from around the air filter box (i couldnt before). but there are a whole bunch of vac lines right there, and i dont know how to locate the leak. all of the tubes look intact.

i also noticed that when i disconnect the EGR, the thud is alot worse, even though i plug the loose end. maybe this is just because the reduced power causes the trans to shift harder.

so how can i find this leak and fix it?

thanks