Mercedes-Benz Forum banner

1 - 20 of 22 Posts

·
Registered
1996 S420
Joined
·
31 Posts
Discussion Starter #1
Started fine, idles OK until it just switches to missing and slightly surging. Good oil pressure, coolant up to temp, charging good. No Codes present. Warmed up to temp, seemed to run fine again until it just starts running bad, slightly surging, paused on an up shift, and when I parked it seem to smell from exhaust. Help on any suggestions... Thanks
 

·
Registered
w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
Joined
·
2,196 Posts
Started fine, idles OK until it just switches to missing and slightly surging. Good oil pressure, coolant up to temp, charging good. No Codes present. Warmed up to temp, seemed to run fine again until it just starts running bad, slightly surging, paused on an up shift, and when I parked it seem to smell from exhaust. Help on any suggestions... Thanks
1996 - 23+year old MB.....
smell from exhaust is a pretty vague term....describe what kind of smell.
Check all your vacuum lines for cracks, breakage.... maybe even disconnected.
No mention of CEL but still, Scan and post any codes. :)
 

·
Registered
1996 S420
Joined
·
31 Posts
Discussion Starter #3
No CEL, smell funky like eggs (old time converter smell) All line are fine. It will run great then just start running bad
 

·
Registered
w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
Joined
·
2,196 Posts
You checked and you're absolutely sure no cracks in any of the vacuum lines?? :)

Simple steps first...
Disconnect the MAF and see how it runs without connection.
Also, get some CRC MAF cleaner. Remove and clean that MAF. Let it dry (dries fast) and reinstall.
 

·
Registered
w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
Joined
·
2,196 Posts
Lines fine, double checked. Why the smell you think? and why no codes
Could be your cats. rotten egg smell - unburnt fuel. test them with a temperature gun - easy test
No CEL - could be on the verge of codes. NO CEL - doesnt mean there are no saved error codes. Still need to scan to verify. It's just the way life is.

 

·
Registered
1996 S420
Joined
·
31 Posts
Discussion Starter #7
Put scanner on it, No codes and O2 seem fine ( no excessive fuel down stream) But I agree that smell use to be from converts. Remember it runs great then poorly then great again.
 

·
Registered
w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
Joined
·
2,196 Posts
Where are you scanning from? OBD2 or 38pin port?
Purge valve? maybe...
You should also look at your STFT and LTFT readings
 

·
Registered
w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
Joined
·
2,196 Posts
I hate turning my head sideways to look at scan readings. Repost them right side up. ;)
 

·
W140 Moderator
"CHRIS" Merc 92 600SEL / Sold > 93 600SE / 93 S500 / 89 560SEL / 413CDI / B180-CDI /A170-CDI
Joined
·
7,599 Posts
Egg smell from exhaust is your Oxygen Sensors Gone ,Replace them 1st . They wont show a code on the scanner but will make a mess of the engines & codes .
The pics you trying to upload will always upload sideways ,it's the format you choose & size , Benzworld re arranges them automatically .
 

·
Registered
1996 S420
Joined
·
31 Posts
Discussion Starter #15
I will try O2 sensors. It did throw a O2 code awhile ago but it cleared and seem to read OK on scanner. Has 147000 miles there due anyway. Thanks
 

·
W140 Moderator
"CHRIS" Merc 92 600SEL / Sold > 93 600SE / 93 S500 / 89 560SEL / 413CDI / B180-CDI /A170-CDI
Joined
·
7,599 Posts
I will try O2 sensors. It did throw a O2 code awhile ago but it cleared and seem to read OK on scanner. Has 147000 miles there due anyway. Thanks
I Suggest OY sensors because you mention Egg Smell from exhaust ,if your Cats would be bad ,you would loose a lot of engine power so test them before replacing as they are expensive . Must be a good scanner you got there to show that code.
 

·
Registered
1996 S420
Joined
·
31 Posts
Discussion Starter #17
Cat,s probably OK because the smell only happens when it suddenly starts to run rough and surges. Then it might stop and run fine.
 

·
Registered
1996 S420
Joined
·
31 Posts
Discussion Starter #18
Hi again, Is the ( in/hg) seem low to you. I had scanner back on and it would read as high as 16.5 in/hg to 9 at idle. Not throwing MAP code though. Also the shrttrim% would go to -25.0 when running rough. Lnogtrim% -5.5
And the MOT purge valve would click but not all the time, is that normal?
 

·
Registered
1996 S420
Joined
·
31 Posts
Discussion Starter #19
Well Map I think is OK but my value at idle for the MAF was 2.733 lb/min when surging and .655 when not.
 
1 - 20 of 22 Posts
Top