cfrantz

I have been through this forum for several weeks researching this issue. The amount of information is awesome and has been very helpful. However, I have been unsuccessful resolving the issue with my car. So here is my history, This car has set for 4 years, I have inspected and cleaned the plug, cap, and rotor. I pulled the FD and injectors and cleaned and bench tested them. I pulled the throttle body and re-calibrated the throttle position switch. After reinstalling all removed, cleaned and inspected components, the car ran like new. I drove it about a mile and it started surging and stalling and now had a dead miss. I once again pulled, cleaned, and bench tested the injectors. This solved the dead miss but the surge and stall still remains. So I went through all of the threads on this issue since 2002 and have tested the OVP - good, Potentiometer - good, fuel pressure - good, injectors - good, throttle switch - good. I will be doing a duty cycle test this evening but any ideas would be helpful in case there is something new I haven't read yet.

cfrantz

As I stated in my original post, I did the duty cycle test last night and came up with a duty cycle of 97.61%. I unplugged the oxygen sensor and the duty cycle remained at 97.61%. Key on engine off is 97.61%. There is no change in duty cycle. I will be performing a test on the oxygen sensor this evening to verify if it is defective.

herrick9

You might consider a fresh Fuel Pump Relay (FPR) given your symptoms.
K.A.E.: 003 545 24 05. (OEM)
Lots of qualities and prices out there but seem to have better longevity with the German stuff when it comes to the electronics.
If you want to go the hardcore route and can get the case off, you might consider re-soldering the connections and then re-sealing bottom section with something appropriate.

cfrantz

I appreciate your response. Thanks. I believe the fuel pump relay is working properly. I have investigated this issue with these W124, M103 cars for some time now. It seems the rough idle stall issue has been resolved through various solutions. Components that lead to this issue are as follows:
Over Voltage Protection Relay - OVP
Air Flow Potentiometer
KHA valve
Fuel Distributor
Injectors
Oxygen Sensor
Fuel Filter
Fuel Pressure Regulator
Fuel Pump
Temperature Sensor
Coil
Spark Plugs, Wires, Cap, Rotor, Backing Plate.
Idle Air Control Valve
Vacuum Leak
Low Voltage, Voltage Regulator, Alternator, and/or Battery
ECU


So the bottom line is that it is almost impossible for anyone to declare a definite solution to the problem. However, the related post have given me the ability to test the components that could be at fault, and through process of elimination, narrow down the issue.


By the way!!, The post in regards to Duty Cycle are not a one size fits all rule of thumb. I believe most cars can be checked for duty cycle, via the % or duty cycle feature on the volt meter, mine however can not. On my 1987 Mercedes 300E, I have to use the voltage setting and the translate that reading into duty cycle. For example When I start the car I get a reading of 6.8V, the formula (Volts / 13.6 - 1 ) has to be used to convert it to duty cycle. So therefore 6.8 / 13.6 - 1 = 50% duty cycle. I have read many post dictating that this is the way to check many issues, however from my experience, the only thing this is good for is to adjust fuel air mixture IF the all other components are operating properly.

cfrantz

Update on my testing and findings in regards to the rough idle and stalling. My very first test I did was to test and clean the CIS injectors. After doing so the car ran perfectly. I drove it to the gas station, filled it up and it promptly stalled and died upon leaving the fuel pump. After getting it home I pulled the injectors again and retested and cleaned them, just in case trash was still in the fuel system. Once again they tested "fine". So for a week I have been testing various things and finding no faults in the system. Yesterday, I read a post indicating that faulty spark plugs could still remain. So I started pulling sparkplug wires to see if there was a change in idle. Low and behold cylinder #1 no change. I pulled cap rotor and plug, cleaned, verified everything was working, plenty of spark. I put it all back together and no change. I pulled the injector for the third time, checked it, and it is now spraying erratically and bleeds down. I will be ordering new injectors today. It seems that this may explain why the car runs fine one minute and then rough the next. I will keep you posted.

cfrantz

It has been a few days since I was here but I have some updated information. I have pretty much tested every component in the vehicle that can be tested. I even removed the security control box just in case. I have replaced all of the sensors, due to them being inexpensive, and replaced all of the injectors. I have adjusted the air fuel mixture and the idle. The car runs like a new sewing machine. You wouldn't believe how smooth and quiet this car runs. Now for the but,,, I can start the car and let it warm up to operating temperature. I drive off with plenty of power and the wind in my hair. I get 3 blocks from the house and stop at a stop sign, a little flutter. I accelerate from the stop sign and a slight studder / stall. I stop at the stop sign at the next block, a little flutter. I accelerate from the stop sign and a worsening studder / stall. I turn around and head home and by the time I make it to my driveway I'm lucky if I can get it into the garage before it completely dies. Now, I have done this test scenario 4 days in a row. Exactly 3 blocks from the house it begins to stall. I turn around and by the time I get home, 3 blocks, it's stalling so bad I pray it makes into the garage. Every component related to this that I can find test good, however, all my test have been cold test not hot test, except for the coil and crank sensor. Coil tested a smidgen higher when hot and the crank sensor went from 700 ohms cold to 1000 ohms hot. Any ideas? ?

Mylesph1

You listed the idle control valve as a potential problem - have you cleaned and/or tested that?

I had a similar problem with my '89 300CE (M103 two valve motor, same as yours). Everything was great until it warmed up, then it would stutter badly and sometimes stall. Like you, everything seemed fine, then I read about the ICV issue.

Pulled it out, blasted it with brake cleaner, cleaned it out, lightly sprayed some WD-40 and wiped it down... problem solved.

If you pull the ICV out, then reattach power while holding it, you can look into it as someone tries to start the car, and make sure the flapper is moving.

Here's a link with a video showing someone dealing with it - jump ahead to the 2:00 mark to see what's up -


Hope that helps.

cfrantz

Thank You for the reply. Yes, One of the first components I tested and cleaned was the idle air control valve. As other users have done, I have tested and or replaced just about every component there is concerning this stutter/stall issue. Last night I replaced the crank sensor, oxygen sensor, and OVP. I as many others believe throwing parts at a problem is a costly endeavor but all has not been in vain. This car runs great, just as long as I don't drive it. LOL. All of the above listed parts that I have replaced have been corroded, deteriorating, or non-functional so needed but not the solution I was looking for. With that said, a new symptom appeared. As I have previously posted, the car runs great as long as I don't drive it. Full throttle and proper response. I drive it for 3 blocks and the surging begins. Last night however, I started the car and while it was warming up I depressed the accelerator and it instantly began to stutter and stall. I release the accelerator and it resumes its perfect idle. I depressed the accelerator again and full rev. I repeated this over and over again and my result was intermittent stutter/stall prior to being driven. I test drove the car and did not even make it two blocks and it began to stall so badly that I had to rev it up in neutral and power slam it into gear in order to make it back to the house. Sooooo, with all of the parts I have already replaced, I started all over again and began testing components I had already verified were good. I began with the potentiometer, here is my findings. Engine off key on, car hot - air flow plate at rest / 0.13 volts, I touch the plate and voltage jumps to 0.22 volts, release and voltage drops to 0.08 volts, touch it again and voltage jumps to 0.25 volts, release and drops to 0.13 volts. Fishy! I depress the plate gradually all the way to the bottom and I get random yet steadily increasing voltage. Test number two, ohms test. I have read that ohms should be between 3.6k and 4.4k on terminals 1-2, I get 8k, I have also read that ohms should be between 576 to 1076 between terminals 2-3, I get 221 ohms. now the test between terminals 1 & 3 I have read is to be between 3.6k and 4.4k and I get 4350 ohms. I have also read that the test between 1 & 3 is the important test but it just seems weird that my first two test are out of spec and the third one in spec and I am suppose to only pay attention to the third test. Fishy! Anyway I ordered a new potentiometer today so we will see what happens when I install it. If anyone can expand on the potentiometer testing procedures and my findings, Please, let me know what you think.

Mylesph1

Man, that's really nuts. When it starts fine but needs time to develop the issue, I wonder if a fuel line is pushing some debris around that slowly causes a bad blockage. Weak fuel pumps, fuel line flow issues, maybe a collapsing vacuum line?

And then I wonder about a clogged cat, or something downstream of the motor, as opposed to upstream with air/fuel mixtures.

I'm going to hope it's a small thing. Which might be infuriating after all this time, but you've certainly made a good faith effort to fix it.

Looking forward to hearing the resolution...

junkyarddawg

In the scope of covering the basics on this cis-e system you should be monitoring the fuel system pressure with a gauge, try to break the system down by bridging the fuel pump relay to eliminate it and its influencing inputs for test reasons. I like to monitor the milliamp readings at the EHA with a series test harness so you can see what the command values are and try to make sense of them, and ill admit that its been 25 years since I had a problem case like yours, but, I think you can unplug the EHA and drive the car, especially if its already warmed up when you unplug it. It will run very sluggish, because there will be no acceleration enrichment, but I don't think that will make it stall out. These tests can help you try to divide the base mechanical system from the electrical system so further deductions can be made without spending money.
Also, some sort of measurable ignition coil output test should be performed to determine that the coil output at the spark plug is within specification. We used an engine oscilloscope but there are cheaper test tools available. Most of these cars were driven with worn out, high resistance, secondary components like caps, rotors, and wire resistor ends, for years and that really takes a toll on the coil as it is at full output all the time.
Divide and conquer

cfrantz

Thank you for your responses. If nothing else this has been a very educational learning experience. I have realized that the many post in regards to this issue are extremely hard to diagnose through a site like this. My vehicle had so many under lying issues that all of the parts I have replaced were needed or on their way out. This car now runs perfect at idle and perfect at speed. The issue that remains is the point I try to accelerate to get to speed. I do not have a fuel pressure gauge but if the new potentiometer doesn't solve this issue I will have to invest in one.

cfrantz

It has been awhile since my last update. I have taken a brake from working on this demon possessed vehicle. I recently purchased a CIS injection fuel pressure tester and downloaded the workshop manual which is listed here: http://www.w124performance.com/servi...07MechElec.htm


A wealth of diagnostic information here. I completely tested the fuel system and the fuel system test perfectly within all of the parameters. The EHA test perfectly, the temp sensor, the potentiometer, the leak down, the pressure up, running pressure, fuel pump pressure, flow rate, etc, etc, etc. Everything test perfect on this car, but yet I still have an intermittent hesitation upon acceleration from a stop, that gets worse each acceleration from a stop after that. The ONLY thing I have not replaced are ECU, ICM, and ignition coil. Which test in accordance to everything I can find. I ordered a new ignition coil and will pick up fresh plugs today. I will post results.

cfrantz

HESITATION AND STALL HAS BEEN RESOLVED!!! Whooohooo! I finally received the new coil and put in fresh spark plugs and the hesitation is gone. It seems that even though that ignition coil tested within parameters is was still breaking down under a load. I had a few components on this vehicle that tested fine and were actually bad or on their way out. I am glad I purchased that fuel pressure tester and ruled out the fuel system or I may still be scratching my head. Thank you to all that responded with ideas and concern for my vehicle issue. I hope this post helps someone else in the future.