Bad Hesitation From Stop when A/C is On - Mercedes-Benz Forum

 
LinkBack Thread Tools Display Modes
post #1 of 10 (permalink) Old 07-07-2015, 08:28 AM Thread Starter
BenzWorld Member
 
Date registered: Mar 2010
Vehicle: 1996 E320
Location: Desert SW
Posts: 131
Mentioned: 0 Post(s)
Quoted: 4 Post(s)
(Thread Starter)
Bad Hesitation From Stop when A/C is On

Posting here because my thread over there: http://www.benzworld.org/forums/w202...ne-1996-a.html
is not getting much incoming information.

1996 C280 (W202), picked it up a few weeks ago. Have replaced everything that was throwing a code, including MAF, and got the vacuum leak that was messing up the transmission shifting fixed.

The M-B data port under the hood won't communicate with my mechanic's super-duper code reader, so we're just running on OBDB II codes.

When the A/C is on, trying to take off fast from a dead stop does almost nothing. The car just sounds like a manual transmission in fourth gear going 10 miles an hour and wide open throttle--the sound changes a little, but unlike a manual being lugged too slow, it often never picks up engine speed, and will rarely stall. Backing off the throttle and giving it a tiny bit, feathering it back to zero and then easing back up to no more than 1/4 (ish) throttle often persuades the engine to pick up and give some power.

This is whenever the starting point is below about 800 RPM. At 800-1,000 RPM, it will be a little slow taking off but will go. No problem if rolling and the engine is at or above 1,000.

This gets worse the hotter it is outside. The delay is longer, and feathering the throttle might not even work. It will even stall sometimes. Noticeably worse at 100 F, gets almost un-driveable above 110 F. When it's that hot, it is sometimes hard to get the RPMs up above 1,000 even in neutral.

Then I discovered that if the A/C is off (including just activating the EC button), there's no problem at all.

Fuel economy is also pretty bad IMO: 17 mpg around town, barely 21 on the freeway at 75 mph.

One person has suggested checking fuel pressure at the injector rail, but I haven not yet been able to connect with a gauge yet. But since it never stalls at speed and misbehaves ONLY at the transition from idle to supposed to give power, I don't understand how a fuel pump or filter could be involved with this misbehavior.

So before I throw parts and money at it (like a TPS that is bad but not generating a code...), I would really like some more suggestions about what to check first.

Thanks!
LVAtty is offline  
Sponsored Links
Advertisement
 
post #2 of 10 (permalink) Old 07-07-2015, 01:35 PM
Moderator
 
Date registered: Jul 2005
Vehicle: 90 300E, 99 ML430, 00 ML320, 05 E500 4matic Wagon
Location: WI
Posts: 19,088
Mentioned: 18 Post(s)
Quoted: 930 Post(s)
Lifetime Premium Member
I would post this in the W202 forum and see if there are other owners that may have had this issue also.
Noodles is offline  
post #3 of 10 (permalink) Old 07-07-2015, 04:34 PM Thread Starter
BenzWorld Member
 
Date registered: Mar 2010
Vehicle: 1996 E320
Location: Desert SW
Posts: 131
Mentioned: 0 Post(s)
Quoted: 4 Post(s)
(Thread Starter)
Quote:
Originally Posted by Noodles View Post
I would post this in the W202 forum and see if there are other owners that may have had this issue also.
BTDT, thought I had already told you.

"my thread over there: http://www.benzworld.org/forums/w202...ne-1996-a.html
is not getting much incoming information"

but thanks for the suggestion.
LVAtty is offline  
post #4 of 10 (permalink) Old 07-07-2015, 07:28 PM
Moderator
 
Date registered: Jul 2005
Vehicle: 90 300E, 99 ML430, 00 ML320, 05 E500 4matic Wagon
Location: WI
Posts: 19,088
Mentioned: 18 Post(s)
Quoted: 930 Post(s)
Lifetime Premium Member
I did not know that.

Has scan tool that is capable of reading all MB specific codes or a real MB star computer been used to check for codes?
Just because the CEL light is not on does not mean ther are not active or stored codes.
Noodles is offline  
post #5 of 10 (permalink) Old 07-07-2015, 10:29 PM Thread Starter
BenzWorld Member
 
Date registered: Mar 2010
Vehicle: 1996 E320
Location: Desert SW
Posts: 131
Mentioned: 0 Post(s)
Quoted: 4 Post(s)
(Thread Starter)
Pretty sure the CEL is burned out. It never lit even when there were codes for MAF, IATC, purge valve, and vacuum leak jacking up the transmission shift delay.

Two different code readers say they are all cleared out. No codes now, it still does it.

Nothing available has yet been able to communicate through the round M-B port under the hood. All has been OBDB-II.

Honestly, I'm tired of repeating all this.

Didn't get above 97 F today while driving, so it behaved better than last week.

There is one suggestion I received by e-mail but it must have been deleted here--check A/C compressor for signs of failure. Will have access to high side gauges tomorrow afternoon. What I understand of theory says that compressor "drag" could explain the lousy gas mileage, but I remain unsure how having no problems at idle from such a problem could result in the WOT does nothing symptom. Compressor drag has to be less than the resistance of pushing the whole car from a dead stop. If the compressor alone could do that, then why can the car move out with the compressor off? One plus the other = too much??? What about taking off uphill? That doesn't make sense to me but I will check it out.
LVAtty is offline  
post #6 of 10 (permalink) Old 07-08-2015, 07:00 AM
BenzWorld Member
 
Date registered: Feb 2015
Vehicle: 1998 C280
Location: Decatur, Alabama
Posts: 96
Mentioned: 0 Post(s)
Quoted: 7 Post(s)
It seems that the key to your diagnosis is the A/C EC button. Turn on the EC button and all is well. Turn it off (and A/C compressor on) and you have a problem. My guess is compressor works acceptably at idle, but has a speed where it drags worse and once it gets over that speed it works better, but your fuel economy suggests it still is working harder than it should. Gauges would help, but the pressures may not be affected that much, since you observe normal A/C?

An additional diagnostic you could do without gauges connected is monitor the pressure sensor reading with the climate control unit. Mine is number 07 in the diagnostic mode (it reads in atmospheres). It should be running between 15 to 20. The beauty here is you can see if the compressor high side pressure is going up at the same time your stalling is appearing. Could have blockage in the condenser or compressor discharge. Good luck!

Jerry

Last edited by Franklyspeaking; 07-08-2015 at 07:45 AM.
Franklyspeaking is offline  
post #7 of 10 (permalink) Old 07-08-2015, 03:27 PM
BenzWorld Member
 
Date registered: May 2004
Vehicle: 300SD
Location: Cleveland
Posts: 50
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Could moisture in the a/c freon line cause blockage and the high pressure sensor for the compressor be defective? I believe there is a fuel chiller on the car too, but doubt if that could cause any problems.

1993 400e
1987 190D
1984 6.2 suburban
2001 e320 4matic



https://benzbonz.biz/store
mespe is offline  
post #8 of 10 (permalink) Old 07-09-2015, 12:33 AM Thread Starter
BenzWorld Member
 
Date registered: Mar 2010
Vehicle: 1996 E320
Location: Desert SW
Posts: 131
Mentioned: 0 Post(s)
Quoted: 4 Post(s)
(Thread Starter)
I got my hands on a gauge manifold with hoses long enough to run into the cabin and expect temps a few miles away to get above 100 (monsoonal rains where I live, still not hot today). We'll see what the high and low sides read during any "events" if I can replicate any, and while running under what appear to be normal conditions too for that matter.

Ran the CCU diagnostics and no permanent codes came up. The intermittent codes were:

226
232
233
416
417
419
421 and
422

the 41 and 42 series don't show up over here: http://www.benzworld.org/forums/w202...diag-code.html
but they are in a .pdf from one of those Russian sites. Pretty sure I cleared out the CCU codes but I have to check--the cancel "erase" might have happened in my rush to get it back to automatic...

I'm going to wait for pressure readings before digging deeper into those codes.

Thanks for the suggestions.
LVAtty is offline  
post #9 of 10 (permalink) Old 07-09-2015, 02:36 PM Thread Starter
BenzWorld Member
 
Date registered: Mar 2010
Vehicle: 1996 E320
Location: Desert SW
Posts: 131
Mentioned: 0 Post(s)
Quoted: 4 Post(s)
(Thread Starter)
Well, here's the data:

ECC Codes have been cleared, not even the intermittent ones show any more.

Ambient 83F
at idle, reads about 600 rpm on the tach
High side 205 PSI
Low side 35 PSI

at 2000 RPM, parked, no other load
High side 125 PSI
Low side 26 PSI

A few minutes later,
Ambient 87F
at idle, 600 rpm
High side 180 PSI
Low side 26 PSI
While sitting, it increased to Hi 245, Lo 35
BOGGED DOWN 2 SECONDS ON A WOT TAKEOFF then moved out when I pressed the EC button

Ambient 95F
On the road, 2,500 RPM
High side 120 PSI
Low side 27 PSI

Short time later, 4th gear and 1,500 RPM, on the road
Hi 160
Lo 22

Pulling onto the freeway about 25 minutes into the drive
Idle 600
Ambient 95F
Hi 200
Lo 22
NO BOGDOWN ON TAKEOFF

Next hour +
70 MPH
Ambient staying at 95F
2650 RPM
Hi 150
Lo 27.5

20+ minutes later
all the same
Hi 150
Lo 24

30 minutes after that
same except ambient is 94F
Hi 145
Lo 23

20 more minutes later
Same ambient
At 600 RPM idle
Hi 180
Lo 28
LAG ON TAKEOFF, A bit more than a full second.

Will leave the gauges in and report more. Should get close to 100F sometime today.
LVAtty is offline  
post #10 of 10 (permalink) Old 07-09-2015, 11:21 PM Thread Starter
BenzWorld Member
 
Date registered: Mar 2010
Vehicle: 1996 E320
Location: Desert SW
Posts: 131
Mentioned: 0 Post(s)
Quoted: 4 Post(s)
(Thread Starter)
Highest it got was 98F. The problem was rarely repeated. High side pressures never got above 245 early on. While driving, 1,500 RPM or more, it was almost always within 5 PSI of 150.

My guy says these pressures are actually on the "good" side for above 90F. Unlikely to be the reason for poor fuel economy.

After the first leg of the trip, the CCU still had no codes, too
LVAtty is offline  
Sponsored Links
Advertisement
 
Reply

  Mercedes-Benz Forum > General Mercedes-Benz Forums > General Mercedes-Benz

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
     
    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page
    Display Modes
    Linear Mode Linear Mode



    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are On
    Pingbacks are On
    Refbacks are On

     

    Title goes here

    close
    video goes here
    description goes here. Read Full Story
    For the best viewing experience please update your browser to Google Chrome