I agree. It has to be a fuel supply / pressure problem or a very slight vacuum leak that is hard to find.

Remember, my terrible oscillating idle problem turned out to be a vacuum leak at the intake manifold seal, but it only occurred after the car had reached operating temperature.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

How can check the intake manifold? By the time I remove the air cleaners, I don't think I want to spray carb cleaner around the intakes looking for a vacuum leak.

On my car, the airbox is to the left, and the intake manifold is on the right. Don't know how the V8 is set up.

However, you can just spray water at the intake manifold gasket. If the gasket is bad, you will get air bubbles.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

I sure am glad you guys are talking about this subject as my 89 420 does the same thing but only slighly and about 10-20 seconds max. Then smooth as a whistle. Its a little annoying but not to the point of seriousness yet.

My mechanic told me its probably a leaky injector, but now I'm wondering as it hasn't been checked yet. With 105,00 miles I would think injectors would be O.K> but you never know.

Will keep up with your verdict. Thanks for the new light shed here.

Keith D

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1989 420SEL 105575 miles
Pearl Black/Grey

1990 Chevrolet E-Cab C-1500
293,000 miles

1989 Olds Toranado Trofeo'
132,000 miles

Correct me if I am wrong this only happens on cold starts right, if so did you check the cold start circuit. On the 117 engines there is an additional cold start injector to increase fuel volume for the initial start this goes away once up and running. Not sure if I am even close as I am unfamiliar with the newer post 92 engines.
hope this helps.
martin

I'm sure if there is a "cold start circuit" on this engine in '95; I'll check into that.

Assuming there is, let's figure this into the mix --- if I turn the ignition to key to "on" and wait 10 to 20 seconds before starting the engine, then rough starts don't occur (I think). Why "I think"? Because, sometimes the car kicks over just fine, other times it is this rough, rough start. The rough starts seem very random.

If was a circuit failing, I'd expect the results to be consistent and repeatable. This problem is more random (or at least seems that way since we don't know what the fault is). I'm not saying that the "cold start circuit" can't be the cause, it could be. What I am saying is, I would think the symptoms would be more consistent if the "cold start circuit" or some derivitive thereof because either the circuit is open or closed.

Yes, no???

As an aside to this; I went through records since I've had the car (purchase it with 68k miles) and the fuel filters have not been replaced. I told the shop to replace those. It's a cheap replacement, so we might as take those out of the equation a possible factor. FYI - the car has 96k miles on it.

Wow, your fuel filters should be changed every 30,000 miles. That could cause a restricted fuel supply problem.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

Yeah, yeah, yeah... I know and ASSUMED they were changed at the 90k check up. It's alittle embarrassing to admit. If that is the problem - alot of money spent for no reason. I asked the shop to double check whether they replaced them or not at 90k service.

John, if you let the key stay on for a few seconds and then start without idle issues then I think you have found your problem. When you turn the ignition the fuel pump starts up and pressures the system if you start straight away it does not get the chance to pressure the system enough. I would agree with you on it not being the cold start system now. Another way to pressure on old cars is to turn the ignition a couple of times as the fuel pump only runs for a predefined number of seconds.
I would look into why you are losing the pressure. Which is where you are already. Sorry was not much help
martin

His fuel accumulator should be maintaining pressure in the system indefinitely. He wouldn't really need to put the key in the on position and wait for any interval of time at all.

If his system is not holding pressure overnight, then the problem would surely by the accumulator.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

good point suginami. So he has a leak after the accumulator as turning the fuel pump on repressurizes the system, or his accumulator is not holding the pressure.

That is my guess.

I'm not a technician, but I stayed at a Holiday Inn Express last night.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

They are still working on the car but feel they have located the problem - the crank sensor. The tech tapped the connection point and the engine died. After playing around with alittle, they said the vibration went away, etc., etc. They didn't find any problems in the fuel pressure check.

So, that crank sensor wire/connection, whatever you want to call it is being replaced. They also recommended a new spark wire set; it has the original w/ 96k miles on the clock, so I might as well replace it. And of course, fuel filter replaced too.

I was worried that it might the timing chain - stretch or that the guide rails were chipping apart. It seemed alittle earlier for that, but I'll drop the car into 3rd and 2nd with out any hesitation while passing cars on the freeway. A quick 50 to 100 mph accerlation is always good

I should get the car back in a couple hours, so I'll post update this weekend after I've put the car through its paces.

Good good good.

I wonder what a crank sensor is. I've never heard of one.

I agree that it's a great idea to put it in a spark plug wire set and coil wire. Have you replaced your cap and rotor yet? I've read that these M119 engines are hard an caps and rotors. I usually replace cap, rotors, and wires in sets. In fact, I usually do plugs at the same time, too, for piece of mind.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

Just car the back; no difference... errrggghhhh... It's going back Monday anyway because they didn't get the wire set on. That could the vibration at idle problem, but I would expect more dramatic problems.

The cap & rotors were replaced at the 90k service.

I think the crank sensor only plays a part during engine set-up, not sure though. It determines the position of the crank shaft; I've read about in one of the other posts here. I'll try starting it a couple different times after varying time intervals and see if the cold start issue is gone.