Cause of miss at idle? - PeachParts Mercedes-Benz Forum

Cervan · #1 08-31-2007, 08:31 PM

http://s8.photobucket.com/albums/a2/Cervan/?action=view&current=Video021.flv

It will miss consistanly on one cylinder, and then sometimes hit or miss on another. i cracked the injector lines while it was running, 1 and 2 seemed to be the culprits, while 3 and 4 were both hitting pretty hard steadily. so tonight im going to be swapping injectors from my old engine, they both have pintles and i tested them, they pop at 115 bars, and have a good spray pattern.

JimmyL · #2 08-31-2007, 11:10 PM

Geez, that doesn't sound good......

Cervan · #3 08-31-2007, 11:14 PM

yeah its knocking pretty badly. the main reason for this post is to show what injector nozzles will do to an engine, even if it has no smoke at high rpms.

#4 08-31-2007, 11:21 PM

That sounds more mechanical than fuel.

Cervan · #5 08-31-2007, 11:24 PM

Quote:

Originally Posted by ForcedInduction

That sounds more mechanical than fuel.

Well as i said, you crack the injector lines on one and two and it seems to even out the engine, The engine has good power, doesnt burn a drop of oil, and has Great compression, dead cold no glowplugs starts right up. so im assuming that the injectors are original and need replaced. Oh and one more thing, it doesnt run like this when its cold, only when it reaches operating temperature (wich is about 90C or so thats where it hovers) So what would cause this if its not injectors?

Cervan · #6 09-01-2007, 05:02 PM

i swapped injectors last night, but im still having the same problem but it seems to have gotten better! I took a video of the engine and such, and now it has a persistant knock on one cylinder http://s8.photobucket.com/albums/a2/Cervan/?action=view&current=Video023.flv but now atleast one cylinder most of the time doesnt miss anymore. Ill be pulling the other two injectors to see if they are the culprits tonight. Oh and when i took out the heat shields, i noticed that #1 and #2 both had diffrent pre chambers, ill show you the pictures.

http://i8.photobucket.com/albums/a2/Cervan/Image077.jpg
http://i8.photobucket.com/albums/a2/Cervan/Image078.jpg

Cervan · #7 09-03-2007, 08:31 AM

Update, i recently replaced all the injectors (with newer ones, that i pop tested they arent "brand new but they are good enough) i cleaned them up with a brass brush and Advanced the timing by 2 degrees the results are astounding. You all saw my last 0-60 times, 32 seconds This one should blow that out of the water. I took a video of this, but it didnt turn out so well, since its so dark outside, ill take a video tommarow and post it.

Cervan · #8 09-03-2007, 09:12 PM

Ok, here are the videos

http://s8.photobucket.com/albums/a2/Cervan/?action=view&current=Video003.flv
This was of before i cleaned the injectors and advanced the timing.

http://s8.photobucket.com/albums/a2/Cervan/?action=view&current=Video026.flv
This is after, it seems to run so much smoother especialy when hitting the higher rpm's.

Now i have one problem, one cyilnder is knocking pretty consistatnly, ive swapped injectors three or four times on the cyilnder i belive it is, ive also checked the valve lash and run lucas diesel injector cleaner through the engine. (Wich that did nothing more than make the engine run abit hotter than usual)

barry123400 · #9 09-03-2007, 10:58 PM

If you have fairly fresh glow plugs read the milli volts they are producing individually. This would help to indicate if the injection pump is sequentially timed properly.
In fact if you were to post the results others may learn from them. At a minumun it will clear or indicate the pump. You are looking for the knocking cylinders glow plug to be a few milli volts higher than the others. Running hotter because of earlier injection.
Swap glow plugs if you get a result to verify it is not just the glow plug tollerance. I assume this knock is not the infamous number one rod bearing as the engine was rebuilt.
Someone out there may have another ideal. Judging by your improved acceleration your overall timing is possible optimal. You may have one pump element leading the others a little is what I am thinking. Not too hard usually to correct for one cylinder if the others are more or less equal in output.

Cervan · #10 09-15-2007, 03:20 AM

Allright, so i checked and swapped out my injectors, i still have this bad idle, ive noticed now that the shake doesnt come with Temperature so much as Oil pressure... wich leaves me tottally stumped.. then i thought about it, the injectionpump is oiled by the same oil thats in the crankcase, when its cold the oil is thick, maybie helping the elements on one cylinder seal up? and then when it warms up and the oil is abit thinner, it becomes too great. ive noticed that my oil is abit on the milky side too, think i should change out my injectionpump? or try new elements? i have a spare in my garage.

toomany MBZ · #11 09-15-2007, 05:38 AM

Quote:

Originally Posted by Cervan

ive noticed that my oil is abit on the milky side too,

This sounds like water is being mixed with oil. Not good, attempt to locate problem...Soon.

Cervan · #12 09-15-2007, 07:32 AM

Well thats the thing, when i say milky i dont mean water with oil, i mean diesel with oil. (sorry that was a bad metaphore im really tired) it doesnt use any oil, or water and it holds pressure.

toomany MBZ · #13 09-15-2007, 02:18 PM

Quote:

Originally Posted by Cervan

Well thats the thing, when i say milky i dont mean water with oil, i mean diesel with oil. (sorry that was a bad metaphore im really tired) it doesnt use any oil, or water and it holds pressure.

Whew!

winmutt · #14 09-15-2007, 05:35 PM

Did you check your PC balls?

rick surgent · #15 09-15-2007, 07:31 PM

have you done a compression check?