W124 M103 1987 260E rough idle - PeachParts Mercedes-Benz Forum

sjsfiji · #1 07-22-2015, 12:43 PM

The car has been running rough while idling for about 3 months. The power during acceleration it used to have isn’t there on the freeway. The roughness got worse gradually. Last night 2 minutes into my commute, it stumbled hard but recovered. This happened twice. When I got home 5 minutes later, the car stumbled and did not recover. I turned her off and restarted. I noticed it would start smooth and progressively get rough--earthquake type rough--within 10 seconds and would not recover and doesn't shut down. I replaced cap & rotor along with spark plugs (1 was broken), cleaned the ICV, and checked vacuum lines and rubber connections. I restarted the car, which was cold, and it was smooth but got progressively rough again like before in no time and my garage smelled like gas. I’m thinking it’s the O2 sensor. Any thoughts?

Best Regards,

Andrew

PARSHOOT1 · #2 07-22-2015, 10:23 PM

Your comment that you smelled gas makes me wonder if it's fuel system related as opposed to electrical system...plugs, rotor, etc. What's the history on the fuel filter, pumps, etc.?

sjsfiji · #3 07-22-2015, 11:22 PM

Update: I started her up cold 30 minutes ago and she ran fine for 10 seconds. This was how it was exactly last night. Now, I don't smell much of the fuel odor like I did last night. Please advise what would cause this problem esp. when she starts just fine and runs smooth for 10 seconds.

https://www.youtube.com/watch?v=BiV7ZZUWUS0&feature=youtu.be

sjsfiji · #4 07-23-2015, 01:31 AM

I started the car up again and it would run smooth for 20 seconds, progressively get rough quickly, then recover smoothly again before getting rough once more. My neighbor and I think it's the fuel filter or maybe the injectors. When rough the car sounds like it's running on 1 or 2 cylinders, then 3, then 6, then 4, then 2, etc.... I'll replace the fuel filters first and see how that goes. Any thoughts?

sjsfiji · #5 07-23-2015, 01:32 AM

for your reply earlier, sorry late response...

optimusprime · #6 07-23-2015, 05:37 AM

SJS i would 1 clean inside the throttle body with carb and intake cleaner spray.Remove the air filter you will see a flap inside the throttle body gently push it down as you spray in the cleaner. It will get rid of all the old black crud that might stop the flap from closing. Do you know anything about the potentiometer ,this little thing is fixed to the throttle body ,in side its a carbon track this wears out as the metal rubbs it like a radio switch.Might be worth a check .

optimusprime · #7 07-23-2015, 05:27 AM

Sjs what plugs did you use to replace the ones that you removed.? Dont use resistor type plugs m103 engines as they dont like them the resistance is built in to the plug leeds .Not saying this is the problem with your car.

lsmalley · #8 07-25-2015, 02:32 AM

I have a suggestion: remove the air cleaner housing and tap on the side of the throttle body with a metal hammer or wrench.....something that will give it a good knock. Not too hard, but not soft either. Do it with the car off, then if nothing try it with the car on. If that does not work, turn the car on and unplug the eha....I understand you have 10 seconds so it's best to have someone crank it over for you. If the car runs with eha unplugged, leave it unplugged until you can source a working one. If car runs after knocking throttle body, remove the fuel distributor and the throttle body (only remove the tb if you have a gasket to replace the one underneath. Auto zone sells the sheets of gasket material which is what I have now. Works great.) Once the tb is off use carb cleaner to clean the dirt from the moving parts then lubricate moving parts with transmission fluid, per the mb fsm.

sjsfiji · #9 08-02-2015, 11:37 PM

I sprayed some carb cleaner into the throttle body as suggested and now she runs longer, rpm hunts from 600 to 1500, then stumbles but recovers and the cycle repeats. At least now I can run her 'til warm at 80C but still the same symptoms as when cold. I replaced the fuel filter but that didn't improve anything. I checked for leaks around the EHA and there were no leaks. What else can I do to clean or check the throttle body. That looks like the culprit or part of. Any thoughts?

tia,

sjsfiji

lsmalley · #10 08-03-2015, 01:19 AM

If you sprayed carb cleaner into the throttle body and its running longer you should enrichen the mixture a bit. Here is what I did while using a multimeter. Take off the diagnostic cap on driver side fender and use ports 2 and 3. Set the multimeter to read voltage and set the dial to 20. Insert the probes into the # 2 and 3 ports when the car is warmed up and running. If the voltage is (-) negative, swap the probes around. You should see your voltage jumping between numbers, but always remaining within a certain range, i.e., 4.6 through 5.7, something like that. Remember the ranges that the voltage shows in case you need to get back to them. Now you need to access the fuel/air mixture screw which is located under the air cleaner housing. Using a (3mm, I believe) hex key insert it into the open end of the adjustment port and press down, the screw is spring-loaded so once you reach the screw you will feel some resistance. Press down gently and kind of turn the hex key until you feel that the key is inside the screw. Once the key is in, slowly press down and turn the screw 1/4 turn clockwise. Observe the voltage on the multimeter for 15 seconds. You will notice that the voltage readings and range have increased. Wait until it stabilizes, meaning it will slowly go up to its max range then it will begin to jump around in btween its lowest point in the voltage and its highest point. Turn the car off and then try starting it again and see if it helps. If it does a bit or you're not sure give it another 1/4 turn clockwise following the same procedure. Also, be sure to remove the hex key after each turn you the spring doesn't shoot it out.

optimusprime · #11 08-03-2015, 06:36 AM

I would get a new distributor top and rotor ,then if its the same new plug leeds.

sjsfiji · #12 08-03-2015, 12:54 PM

All,

Thanks for the response. The distributor rotor, cap, plugs, leads, and fuel filter have been recently replaced. I measured the leads and they're all 1K ohm +/- 10% so I think they're ok. The EHA has not leaks.

I'll try adjusting the duty cycle as suggested tonight and see if that addresses the stumbling, but it happens when cold (open loop) and hot (closed loop). As such, I doubt it's the mixture, O2 sensor, or cold start valve. The car was running perfectly just before this rough idle/stumbling issue.

I'm thinking it might be dirty fuel injectors and/or fuel distributor or faulty fuel pressure regulator. Anyone else think one of those could be the culprit?

I'll update frequently.

Again, thanks in advance for any insight.

Regards,

sjsfiji

lsmalley · #13 08-04-2015, 04:11 PM

BOSCH KE3-JETRONIC MIXTURE ADJUSTMENT

sjsfiji · #14 08-07-2015, 12:58 PM

I’ve replaced the air filter, fuel filter, injectors (with new top seal, o-ring, & nylon sleeve), plugs, 2 top intake hoses + 2 hoses to the idle valve, and cap&rotor. The ignition wires are fairly new and idle and cold start valves were cleaned. The car runs smoother when not stumbling after replacing the injectors; however, my neighbor who runs a MBZ shop says the culprit is the fuel distributor (FD). He shop runs into a lot of faulty FDs due to age and I think that’s the step in the right direction. Does anyone agree with this? Maybe I should replace the fuel pressure regulator (FPR) and/or thermos/vacuum valve on top of the intake manifold. I didn’t mess with the mixture as suggested since when she runs cold or hot, she purrs. I’ve almost decided to tackle the rebuild myself and order a rebuild kit from ebay. Additionally, I’ll also be cleaning the air mixture assembly and throttle body while I’m in there if I do so. My current laundry list is as follows:

FD rebuild kit
FD gasket
EHA gaskets
Throttle body gasket
Air Flow Meter boot w/ gasket
Thermo/Vac valve (as needed)
FPR (as needed)

Is there something else I should consider cleaning or replacing interms of gasket, o-rings, valve, etc…

TIA,

sjsfiji

sjsfiji · #15 11-30-2015, 10:18 PM

All,

Here's an update...

So far I've replaced cap, rotor, plugs, wires, o2 sensor, fuel filter, injectors, icv hoses, intake hoses, air metering boot, fuel pressure regulator, and fuel distributor with eha and potentiometer (from donor car) and the car would run without stumbling but it was really rich and would not start cause it floods. I gave up and sent it my indy. He replaced a bad temp sensor, adjusted potentiometer and mixture. The car ran with high idle ~1k RMP but won't kick down. I think that's a separate problem or maybe related (enrichment problem?). High idle I think might just be a misadjusted potentiometer. Anyhow, I started the car yesterday and let idle for less than a minute and when I placed it in drive it would stumble then recover. It ran fine when placed back in park. I started her up today just fine and adjusted mixture a little richer and she ran fine/smooth in idle and when in drive with good pick up. I started her up tonight and it was stumbling from the get go then recover while in idle. I'm thinking it might be wiring to the temp sensor is suspect which might actually be the original problem. Any thoughts? The stumbling is more like bucking as if there's no detonation in one or more cylinders, then I smell fuel. I see 3 sensors inline from cylinders 1-6. Can someone shed light on what each sensor does? I have an idea but rather query you. Thanks....