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

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update: injectors replaced, stumbling persists

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

Did you at least test the fuel/air mixture before you go out and buy a new one?

If you're referring to the duty cycle, no I did not change it. I would need to get the car up to temp and rev at 2500 rpm to properly adjust it. At least that's what I've read. I don't want to run the car the way it is. My shop owner neighbor swears she runs just fine when not stumbling and that the FD just needs to be rebuilt. The diaphragm in the FD may have gone bad.

Again, these are all just theories and guesses from your neighbor, but hopefully the rebuild fixes the problem. If not, you will eventually need to start systematically testing the components instead of replacing everything under the hood. I've been through the same exact thing a few months back and replaced almost everything fuel related and ignition related... http://www.peachparts.com/shopforum/3458741-post7.html
Good luck and keep us posted.

Yeah, i hope that fixes it too. At first I assumed the problem was electrical [e.g. spark] so I did the normal tune-up wear items (plugs, wires, cap & rotor). Then we, neighbor and I, realized or at least assumed the problem is intermittent fuel starvation at only certain cylinders, so the plan of attack was fuel filter (wear item), injectors (still had orig steel), then FD. That is where I am at right now and I hope that's the end.

Try this it wont cost a dime ,Remove the hose going to the brake srvo block off the end with a bung ,so no vacumm can get out or air in .Try it now ..I go along with not messing with the mixture this is something simple. The fuel pressure regulator can get blocked up with dirt and rust this is in the same area as the fuel filter... Take a fuel pressure reading also .Do come back and let us know ,easy things first .

Quote:

Originally Posted by Benz Mondi (Post 3500927)

Smell of gas is the classic sign of a leaking EHA valve. Lift off the air cleaner, it's the black box slightly larger than a match box that is bolted on the side of the fuel distributor (the spider looking silver mound that all the rigid fuel hoses go to). Turn the engine on and you'll see fuel leaking out of the weep holes. Good news is that there are plenty of good used ones on eBay for $80 of less (make sure you get a leak-free warranty). You'll also want to get a new pair of O-rings ($7.95). Don't try to find some cheap a/c O-rings as poor substitutes or re-use the old ones. They'll just leak again. EHA O-rings are made of a special compound and are of a specific size that doesn't match anything you can find locally.

Removal/installation is easy: 1) with the engine not running, put a cloth underneath the EHA to soak up the small amount of fuel and, more importantly, the bolts and O-rings that you'll surely drop and never find in the depth of the engine. Unplug the electrical connector at the side of the EHA. Some of the bolt heads require a Torx (should be a T-30) or standard flat head screw driver. If it's a Torx, make sure you use the correctly fitting one. You don't want to strip this. It usually takes more torque that one would think to turn the bolt. BEFORE, you attempt to turn the first bolt, take another cloth and cover the top side of the EHA while you turn the bolt. Otherwise you are sure to get a shot of gasoline in the eyes. Loosen each bolt until the gas leaks out and the pressure is gone. Then unbolt the EHA the rest of the way. Inspect the replacement EHA mating surface to make sure it's completely clean and flat. The same for the mating surface at the fuel distributor. Remove the old green O-rings from the fuel distributor with a pick. Install the new ones, making sure the completely fit inside the recessed cavities. Carefully bolt on the EHA, making sure you haven't dislodged the O-rings. You just need to "hand-tight" the bolts. The fuel pressure will make the fit tighter. Clear the area of the cloths and tools. First turn the key to the on (do not start the car) to pressurize the EHA and check for leaks, then turn the engine on. It should not only idle well, but should not have any leaks. Keep the engine running for at least 5 minutes and increase the RPM's to 2,500 for at least 30 seconds to check for leaks. Done!

I'm quoting this post for personal future reference. I've replace the EHA once, a long time ago. Recently I noticed some fuel smell and plan on checking it again in the near future. Funny thing is, I don't think I replaced the O-rings with new ones last time. This time, I've gotta remember to do that.

Problem fixed then came back... update

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....

In case it matter, the temp in the garage when I last started her up was about 48F.

Going thru quite similar with my 89 300E.
Read a volume of material on the issue, about War and Peace for volume.

The high idle seems to be locked into the IAC. I replaced my IAC with a
gate valve which seems to have eliminated my surging idle but left me with
an idle of about 1K.

Not new to working on cars as I go back to '51 Packard straight 8. Have to say this CIS MB is one of the worst pieces of sheeeet I have ever worked on.

On the positive, once I get this POS running correctly again, its is the last MB I will be working on. Done, done done !!