280e loss of power under acceleration - PeachParts Mercedes-Benz Forum

backpacker · #1 01-21-2004, 04:32 AM

Please help - I have just bought an '83 280 e (w123) with 115k on the clock. It drove fine on the test and then when I got home last night after a trouble free 40 mile journey, I turned into my street and the car just died - picked up - died, etc.

Eventually by pumping the gas pedal I managed to struggle home. I have checked dozens of posts in this forum but can't find the exact problem.

The fuel pump was replaced 2000 miles ago, oil pressure seems fine, I checked 3 of the plugs and they are all fine.

I do know the idle is too high and the engine runs fine in P or N and at a decent speed but as soon as I select D the revs drop and it starts to stall when I press the accelerator.

I didn't think a car this old had any fancy ECUs - any ideas what it might be.

Many thanks!!

neileg · #2 01-21-2004, 06:59 AM

Sounds like an air leak on the intake. These can happen all of a sudden and if your car has seen little use before you bought it, the exercise could have caused a hose to come loose or split.

The vaccuum system for the locks and other functions depends on lots of rubber connectors, plastic pipes and diaphragms. Any of these can fail, and they will mostly be 21 years old now and rather brittle. Do all the locks work, and work smartly? If not there's a leak here.

backpacker · #3 01-21-2004, 08:15 AM

Thank you for your quick post.

You may be right - the central locking system isn't working at the moment (its on my list of little niggles to fix) but I had never thought it would have anything to do with the engine.

I am leaving the car over to a Merc specialist tomorrow for a service and general diagnosis in the hope that he can sort the problem but it is good to know what could be wrong. Will post update next week.

ctaylor738 · #4 01-21-2004, 08:24 AM

Check and see if the main vacuum line came off the intake manifold. If it is still on, try removing the connector and plugging the manifold fitting to see if that improves the running.

backpacker · #5 02-09-2004, 05:35 AM

Three weeks later and I've still got the same problem.

Starts and runs fine for about 2 minutes and is great on the motorway but as soon as I stop at a junction the engine starts missing and when I try to pull away quickly, it loses all power and nearly stalls. Problem seems worse when engine is hot so I was thinking fuel injectors.

So far, I have replaced the Distributor Cap, Rotor Arm, Leads, had the spark timing checked by a garage and just yesterday, bought two new fuel injectors and tried them two at a time in the six cylinders. No change.

I've checked for obvious air leaks but can't find any. Have found that the Ignition Control Box has been changed at some point (don't know when or why).

Can anyone suggest what I should try next - do you think the ignition coil is a possibility even though everything works fine at higher speeds. I'm also thinking Fuel Distributor but that is a bit of a job.

It is really too dangerous to drive now and I am at my wits end - any help appreciated.

Thanks.

hawkpfc2 · #6 02-09-2004, 11:07 AM

have you checked injector seals?

psfred · #7 02-09-2004, 11:15 AM

Does that car have K-Jetronic fuel injection?

If so, I suspect someone has set the fuel mixture with the engine cold and you are going way lean on warmup. Don't neglect to verify the condition of the brake booster, also -- can be a source of a large vac leak.

Set the fuel mixture with the engine fully warmed up and see what happens.

Also, if you have electronic idle control, check the condition of the idle valve hoses -- these get hard and leak around the fittings even though they look fine -- if they are rock hard, replace. Ditto for ALL vac lines on the engine, whatever they hook up to. Any hard rubber connectors must be replaced, and check all the vac servos for leaks -- you may have vac applied to something after the engine is warm that leaks.

I'd personally look for a vac leak -- this will make the car almost undrivable warm while it runs fairly well cold. Fix all the vac leaks before setting the mixture. Otherwise, you will have to correct it again each time you find a repair a leak.

Peter

backpacker · #8 02-09-2004, 12:16 PM

Quote:

Originally posted by hawkpfc2
have you checked injector seals?

hawkpfc2 - Thanks - I fitted six new seals (the black things that go around the injectors) but I couldn't get the plastic injector seats with rubber o-ring. Checked all and looked ok.

Peter - Thanks for your suggestions - I will check for leaks but I think I need to get a vacuum pump. The Haynes manual is absolutely hopeless at mentioning anything to do with the vacuum system. I just don't know what to look for.

The fuel mixture is something else that puzzles me. I tried adjusting what I think is the mixture control (allen key screw in fuel distributor) but when I turned the screw anti-clockwise while the engine was running, fuel started to leak out and I had to tighten it fully clockwise to stop that.

I am going to replace the spark plugs tonight (even though every mechanic says they are ok) and the coil tomorrow night to see if either of these make a difference.

Thanks for the suggestions - I will update progress.

psfred · #9 02-09-2004, 01:49 PM

If fuel came out, it's not the mixture screw, that one only adjusts the relative position of the metering flap and the plunger, it has no fuel anywhere near it.

The mixture screw is beneath a "tower" between the air flow senosr (the flap) and the fuel distributor body (where the lines to the injector come out). May just be in a hole between them, not sure on a 280. Either way, it's only accessable with a fairly long allen (hex) driver -- you must push down against a spring to actually engage the mechanism. May have an anti-tamper plug over it, too. Does on the US versions anyway.

Haynes manuals are almost useless beyond tuneups and minor issues -- the CD from FastLane here will be MUCH more usefull!

Get a hand vac pump with a guage -- will make life much simpler.

The vac systems are color coded -- plain color is supply, color with a stripe is servo -- green for climate control, yellow for door looks, brown for shutoff on diesels, other colors for emissions controls, white for engine controls (including EGR and transmission vac controls).

Peter

backpacker · #10 02-10-2004, 04:39 AM

Thanks.

Ok, update:

Got home last night and changed the plugs even though two garages said existing ones were fine. Engine ran like a dream!! No hesitation, no missing, just pure seamless accelleration. (Thank you to Murray Motors in Belfast for suggesting I try the obvious)

Only snag is that this morning there is still a slight hint of the old problem - not very much and certainly not enough to make a major difference - my only worry is that maybe I have cured the symptom and not the cause.

I am going to go ahead and change the ignition coil tonight as it isn't a particularly expensive part but does anyone have any thoughts on what is happening here?

Is it possible for one of the plugs to be damaged (heat, electrical, etc) that quickly?

Many thanks to all for the help and suggestions - they have helped to keep me calm over the past few weeks.

pmckechnie · #11 02-10-2004, 07:24 AM

One question.

What brand and number plug did you take out, and what brand and number plug did you put in? Also what brand and type plug wires were used? Sounds like a problem I had on my 84 500 SEL.
I had the wrong plugs, and the wrong coil to dist wire, (it was a resistor wire and should be a solid core wire).

backpacker · #12 02-10-2004, 09:01 AM

Hi Paul

I can't remember what the old plugs were - I have them at home - but I put in new Bosch plugs and the wires are Bremi. Coil is Bremi transistorised model as specified by the autoparts store.

My new "best friend" mechanic had a look at them and thought they were good. He had two possible culprits:

1. Rubber valve seals have hardened and oil is getting at the plugs causing them to short circuit and wear in a short time - he is trying to source a rubber conditioner and sealant that is added to the oil.

2. A possible short between the coil and the plug cap despite the changed items - I am changing the ignition coil tonight anyway.

If the problem gets no worse I will be happy as at the moment it is just an intermittent half second hesitation when taking off.

If it is the valve seals, then that's a different matter - will try the sealer, I think Gunk make one.

To be continued...

olpos · #13 02-10-2004, 09:39 AM

before buying any more parts, have you checked the compression.
this helps you know what the car should run like after repairs.
to check coil see what the spark looks like. pull coil wire and have someone crank car over. nice strong spark. coil may be ok
rich

backpacker · #14 02-10-2004, 09:56 AM

Such is my relative newness to this game I don't have a compression testing kit yet. But I like the concept of being able to diagnose a lot better myself.

But even trying to find a stockist of Mityvac is difficult here!! Does anyone know where I can get W123 workshop manuals on CD? I have tried eBay UK and US but there are none for this model.

As for the coil, it is only £28 (about $50) which in the great scheme of things is peanuts and at least I can eliminate it from my enquiries.

backpacker · #15 02-13-2004, 11:21 AM

Final update for this thread:

Fitted a new ignition coil and so far, no further occurance of the problem. I may have damaged the transmission trying to go from neutral to drive whilst revving the engine but time will tell.

Thanks to all who responded - this really is a great forum and a definite benefit to owning a Mercedes.

Cheers!

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