'91 300CE cold and warm start stalls - PeachParts Mercedes-Benz Forum

rgnprof · #1 08-11-2012, 10:27 PM

I know there are a bunch of threads on this (I have even posted before about a warm start issue)....but now I have a cold start problem AS WELL. I crank the car and it fires immediately - just like always, but it will stall out immediately if I don't juice the pedal some. I have had this same issue as a warm start problem for a while now - haven't been able to figure out much. I have changed out the O2 sensor - several years ago now, new OVP, tried adjusting the mixture, coil, plugs and wires (all within the past 2 years now - maybe 15-20K miles ago).

And I'm getting crappy mileage - never do much better than 14 mpg, which is down from 18-24 - mixed driving conditions. Also have a real hesitation upon initial acceleration...and once I get past that it lurches forward and runs much better at highway speeds.

Any advice would be appreciated.

Thanks, ryan

johnflight1 · #2 08-15-2012, 04:37 PM

I am having the same problem for a while now. I have replaced the plugs,wires,cap,rotor,coil,vacum lines,ICV,ICV hoses,valve stem seals,OVP,all injector seals, I have also changed fuel filter and a pump about 18 months ago. I am at a loss for what to do now! let me know how you make out with this problem.

antonino · #3 08-15-2012, 07:10 PM

Dear RGnpROF,

I am having the same problem with my 91 300ce. It starts fine in the morning, runs for 3-5 min and then shuts down and unable to restart for several hours, then same thing all over again. I posted a thread on Sunday and as yet have only heard from one person who replaced his fuel filter and problem went away. I replaced mine yesterday and put in fresh fuel even though I only had 25K on the old filter...problem persists. Hope someone can help us out as this is my summer car and I would love to drive it for a few months before the New England winter arrives.

Antonino

S124300 · #4 08-16-2012, 03:31 PM

Fuel pump relay or ignition control unit?

antonino · #5 08-16-2012, 08:27 PM

I talked to a friend of mine who has an 87 300e. He had a similar problem and it turned out to be the fuel pump relay at a cost of $115. for the part. On the 300ce, however, the pump relay is part of the MAS Control Module located behind the battery...cost, $480. I am willing to spend the money if this is in fact what is causing the problem. I have read a post recently using the search component on this site of a person who had the same issue and took his car to the dealer, bottom line, many parts including the MAS Module replaced at a cost of $2000. and problem persisted...he sued the dealer and got his money back but did not say if he ever solved the problem. I have ordered a new coolant temperature sensor and OVP (overload voltage protection relay) as they are inexpensive and am told could be causing the car to shut down. It starts right up in the morning, runs for 5-10 minutes, starts to miss and then shuts down and will not restart until the next morning. As such, I am thinking my problem could be heat related...will let you know tomorrow if these 2 new parts resolve my problem.

Antonino

rgnprof · #6 08-17-2012, 12:48 AM

Let me try and solve one problem at a time here: My car - once it starts - runs fine, EXCEPT for really poor gas mileage. Doesn't matter if I'm on the highway, or city driving - I'm getting around 14 mpg.

Now, I'm having a cold and warm start problem. In the morning, when I go to start the car it will crank fine, start right up and then stall out. If I crank it again, it will usually stay running this time - after the idle drops to approx 300 rpm's and then kicks up to 500+ rpm. All of this is WITHOUT stepping on the gas pedal.

If the car is warm, it will start right up on cranking, but will NOT stay running unless I give it some gas. Hot/warm starts have been a problem for a while - the cold start problem is new. My understanding is the cold start valve does not operate until temps are below 50F (??), so I don't think this is the problem. I am assuming all of this is contributing to my poor mileage - which of course, could be wrong.

ryan

Ferdman · #7 08-17-2012, 09:14 AM

Ryan, with a bad ignition control unit (ICU) the engine will not start. Just went through that with our 1991 300CE. Keep in mind that MB dealers sell reconditioned ICU's if you ever need one. Even the reconditioned ICU's are expensive though.

rgnprof · #8 08-17-2012, 09:27 AM

By ICU, do you mean the EZL on the drivers side fender? Again, my car starts fine, it just won't stay running without giving it some gas - unless it is really hot. Would this still be related to the ICU?

Ryan

Ferdman · #9 08-18-2012, 02:50 AM

Yes, the ignition control unit is mounted on the driver's side inner fender.

Check the condition of the distributor cap and rotor since you don't mention replacing them when you replaced the spark plugs and ignition wires.

rgnprof · #10 08-18-2012, 08:10 AM

They were replaced at the same time - with Bosch parts...I am going to pull the plugs and I will check out the cap and rotor again, but all of this stuff is relatively new...

ryan

Cal Learner · #11 08-18-2012, 08:35 AM

Quote:

Originally Posted by Ferdman

Ryan, with a bad ignition control unit (ICU) the engine will not start. Just went through that with our 1991 300CE. Keep in mind that MB dealers sell reconditioned ICU's if you ever need one. Even the reconditioned ICU's are expensive though.

Fred, that wasn't my experience when my EZL went south. The motor would start, but it acted like the timing was way out of whack and coughed and sputtered like it was hitting on only about half the cylinders.

Ryan, some of your symptoms are familiar to me too. I saw no mention in your earlier posts about replacing IAC (idle control valve) or the throttle micro switch. I replaced both of those and made a significant improvement. Also, your fluctuating idle RPMs suggest a possible vacuum leak. The two shaped rubber vacuum lines coming off the IAC are the usual suspects for leaks.

rgnprof · #12 08-18-2012, 08:40 AM

Yes, I have replaced the throttle microswitch and have pulled the IAC valve and checked it's operation - and it seemed to be working correctly. I cleaned it out with the carb cleaner and put it back on - and the hoses are not leaking. Although, as I was checking things recently, I noticed that unplugging the IAC did not affect the idle...

Thanks!
ryan

rgnprof · #13 08-18-2012, 12:01 PM

Brief update:

Checked the operation of the O2 sensor as described on this forum and I don't think it is working properly. I got the car warmed up and just as the reading on my multimeter starting fluctuating between .5v and 1.0v - I heard a click from the motor - somewhere, but it was definitely noticeable. After that, the readings quit cycling completely - stuck on 1.04v and it stayed there at 2500 rpm's.

Am I on to something here? And, if so, what?

I should indicate that this is a relatively new, direct replacement Bosch O2 sensor - replaced about 2 years and 15K miles ago.

Ryan

johnflight1 · #14 08-18-2012, 01:17 PM

I still think our problem is fuel related because it is losing its prime. Fuel is running back from the injection system except for the small amount of fuel in the actual injectors which gives it the initial fireup and then it dies till you either continue cranking or restart while feathering the throttle. OK when hot.
Question? What is the function of the EZL will it controll timing because too advanced or retarted will cause start problems..............

rgnprof · #15 08-18-2012, 07:22 PM

Another brief update:

Checked the duty cycle with my Sears meter and discovered that the cycle would not cycle! Everything checked out initially - 70% KOEO and 50% when started...but after the car warms up, the cycle - using the volt reading on my multimeter instead of the duty cycle - goes to 1.02v and stays there, which is the same voltage I was reading when I just checked the O2 sensor voltage. If I increase rpm's, voltage increases some, but then drops right back down to 1.02v.

Never had this happen - I have had some trouble figuring out the duty cycle and have never been able to get it close enough to each other at idle and at 2500 rpm (within 10% or so), but never this...something is wrong!

Help anyone?

ryan