Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help




Go Back   PeachParts Mercedes ShopForum > Technical Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 07-30-2008, 12:02 AM
mus mus is offline
Registered User
 
Join Date: May 2007
Posts: 81
Help me: really rough undrivable, but not all the time

okay, i come back from vacation, start up the car (1992 400e). works fine the first time. smooth.

the next time, it is SUPER rough; bucking, hic-upping, worst on acceleration at low speed/stop. stalls out a couple times when shifting into drive.

it has now done this intermittently since. sometimes its worse than others. at worst the car in un-drivable. some days it goes great no problem. others it does this. if i stop for twenty minutes or so, it usually "resets" and runs smooth. just turning the key on and off does not help. seems perhaps worse when its been sitting out in the heat, but it can do it from cold. One time it was so bad, i gave it gas to get going and a think i heard a thump thump from the engine, like perhaps a backfire through the air intake?

the car has never done anything close to this before. its been smooth as glass.

i cant figure out what would cause this, but only sometimes. i guess it must be electric/electronic. but really do not know

anyway, its off to the mechanic tomorrow but any suggestions or ideas would help.
__________________
Christopher

400e >> 1992 >> 196k miles
Black Pearl Metallic/Grey Interior
Reply With Quote
  #2  
Old 07-30-2008, 12:15 AM
Registered User
 
Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,777
Just a guess
Dist Caps/Rotors......
__________________
A Dalton
Reply With Quote
  #3  
Old 07-30-2008, 01:08 AM
mus mus is offline
Registered User
 
Join Date: May 2007
Posts: 81
i thought about that, but i thought it would be rough all the time in that case. it is like some, from one to many, cylinders are missing.

i should mention perhaps, the wiring harness has been replaced.
__________________
Christopher

400e >> 1992 >> 196k miles
Black Pearl Metallic/Grey Interior
Reply With Quote
  #4  
Old 07-30-2008, 02:00 AM
Registered User
 
Join Date: Sep 2004
Location: Seattle
Posts: 1,899
Well the symptoms are classic bad spark plug wires symptoms. If you have a meter you can ohm out the wires (assuming you can get to them). I am not familiar with that engine. That would be the first thing I would check. I have seen that on several different cars. A friend of mine was going to buy a new car because he thought his car was hopelessly broken. I found a bad wire with my ohm meter and changed it. He was amazed. Ran like new. If the spark plug wires are good then it still sounds electrical as you suspect. So in that case maybe coil, crank sensor......
__________________
1998 C230 330,000 miles
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra
Reply With Quote
  #5  
Old 07-30-2008, 11:15 AM
mus mus is offline
Registered User
 
Join Date: May 2007
Posts: 81
well, the spark plug wires look pretty new, soft rubber, etc. and i think were replaced not so long ago. almost all the wiring in the car has been replaced by the PO so far as i can tell.

I might check the caps and rotors...be great if it was that simple. I know they are something to watch on the m119 engines.

the main issues i am having seem to be electrical gremlins. with the heat of the engine i think these things tend to go...

i have only had the car a year and this is the first real mechanical issue i have had. oh, that and the ps pump almost falling off because two bolt heads sheared off. the mechanic had to drill the rest out...beyond my abilities and flexibility. $300 of labor; $12 parts.
__________________
Christopher

400e >> 1992 >> 196k miles
Black Pearl Metallic/Grey Interior

Last edited by mus; 07-30-2008 at 11:22 AM.
Reply With Quote
  #6  
Old 07-30-2008, 01:03 PM
Registered User
 
Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,777
A crude but effective plug wire test is to spray the wires with a fine mist from a squirt bottle of water as the car is at idle..if they are bad ., it will skip right away.
Another is when the condition comes back, coat all the plug wires with WD40 and wait 5 min..if it clears up..bad plug wires
The problem usually shows up on rainy/humid days..the WD is a moisture
displacement...Original wires were solid core, so you may want to check what was put on there as a replacement. They may have used silicon resistor wires. The spray test will show them right off the bat.

The caps and rotors will be evident when you look at them
__________________
A Dalton

Last edited by Arthur Dalton; 07-30-2008 at 01:29 PM.
Reply With Quote
  #7  
Old 07-30-2008, 02:24 PM
mus mus is offline
Registered User
 
Join Date: May 2007
Posts: 81
okay, this morning i looked. the caps and rotors are shot. all sorts of arcing/burn marks in strange places plus lots of corrosion. i will replace these and see what happens.

if it keeps doing it will check the wires, but they look/feel practically new and i suspect, knowing the shop that has taken care of the car, that they are good quality replacment

fingers crossed...

thanks for the help
__________________
Christopher

400e >> 1992 >> 196k miles
Black Pearl Metallic/Grey Interior
Reply With Quote
  #8  
Old 07-30-2008, 02:29 PM
Registered User
 
Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,777
Very Common and why I mentioned that as first suspect...
Standard Maint. Items
__________________
A Dalton
Reply With Quote
  #9  
Old 08-03-2008, 01:06 PM
mus mus is offline
Registered User
 
Join Date: May 2007
Posts: 81
okay, thanks. changed and seems fine now...i might go ahead and change the spark plugs while I am at it. the wires are fine.

thanks for your help. never expected the distrib to make it that rough...
__________________
Christopher

400e >> 1992 >> 196k miles
Black Pearl Metallic/Grey Interior
Reply With Quote
  #10  
Old 08-03-2008, 01:12 PM
Registered User
 
Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,777
[QUOTE=mus;1928862]okay, thanks. changed and seems fine now...i might go ahead and change the spark plugs while I am at it. the wires are fine.

thanks for your help. never expected the distrib to make it that rough...

I would run the plugs for a week and then check them..now that the caps have solved the problem, the plugs will clean themselves of soot from the misfires.. you will be able to see if they need changing then...........
__________________
A Dalton
Reply With Quote
  #11  
Old 08-03-2008, 01:34 PM
mus mus is offline
Registered User
 
Join Date: May 2007
Posts: 81
okay great. thanks
__________________
Christopher

400e >> 1992 >> 196k miles
Black Pearl Metallic/Grey Interior
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 09:12 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2011 Pelican Parts - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page