W124 M104 bogging when warm + fuel leak

[BlueQuinn]

My 300TE-24 wants more money :-(
There are a couple of symptoms:

A smell of petrol inside the car. I lifted the bonnet tonight when I got home and there was a fuel leak under the air cleaner on something that joins the inlet manifold forward of it.

When it's being driven in traffic, if it's stuck there for very long and everything gets warm then after a while when you pull away from a standstill it will bog down and almost stall and for a while it won't go anywhere. Then if you persuade it go go with a bit more gas then it will zoom away too fast, like massive turbo lag). When this happens the only way to get it to drive reasonably safely is to use the autobox like a manual and start off in 1-2 every time. Even then it's dicey.

I've read about EFAs producing this symptom. Is this it?

 

[carat 3.6]

The fuel leak looks to be coming from the fuel pressure regulator.

As for the bogging down issue check for vacuum leaks first, then see if you have a good spark.

 

[BlueQuinn]

Thanks Carat. I think you were spot on.

The large nut was not tight. I could easily see that starting to leak as it warmed up.
I nipped it up, so hopefully no petrol smell anymore.

I noticed when dismantling the air cleaner, that the air intake temperature sensor appears to be broken.
What symptoms would this cause?

And that I am getting oil entering the engine via the cam cover overflow pipe.

I assume this is by design and OK or it wouldn't be there, but the air intake below the flap thingy is very oily inside as a result. Is that a problem? Do they benefit from dismantling and cleaning?

Also I have a possible leaky PAS reservoir. Should I care too much or do they all do that sir?

 

[carat 3.6]

The pas pump can weep around the front seal, but it doesn't normally cause a problem. Wash it of with brake cleaner and rag, the pump itself will give up before the seal will.

The air intake temp sensor doesn't seem to do a lot on the k-jet cars, there's alot of m103 running around with it disconnected. I doubt it will be causing your bogging down fault, but it should be cheap from a breakers. I've never had to buy one of those so have no idea how much they are new.

The oil residue coming from the breather pipe is normal on the m104, but looking at the oil on your air flow meter I would be tempted to remove the complete metering unit from the engine to clean it out. Thereby giving you good access to clean the throttle body below it at the same time, which could be gummed up with crud.

 

[BlueQuinn]

Thanks. Today it did the bogging down thing again. After once it's nice and warm after a run down the dual carriageway I get to a queue of traffic, and when it moves, I press the throttle and nothing happens. Then everything happens. Seems only to happen when in gear. It will happily rev if it's in neutral.

 

[carat 3.6]

I'd hazard a guess that it's running a little rich, or you have a weak spark.

 

[balge]

When I was trying to sort out the hunting idle on my230TE I looked into this and found this

IAT sensor...does anyone know what this does for the car? - PeachParts Mercedes ShopForum

don't know if it helps?

 

[ray_hennig]

The air intake temp sensor doesn't seem to do a lot on the k-jet cars, there's alot of m103 running around with it disconnected. I doubt it will be causing your bogging down fault, but it should be cheap from a breakers. I've never had to buy one of those so have no idea how much they are new.

I replaced mine some years ago for about €12 from MB so pretty cheap. I wouldn't bother with a second-hand unit.

When the new sensor was fitted, I needed to readjust the fuel delivery as it had drifted significantly off the 50/50%. So, it was worth replacing and may have contributed to today's smooth running.

Good luck.

RayH

 

[BlueQuinn]

The saga continues. I've just spunked damn near £800 on a B service including a new intake air temp switch, fuel system clean, and it's made absolutely no difference. The car is basically undriveable in traffic.

So we can rule out the intake temperature sensor, and the car being out of tune. What the hell is wrong with it?

It only occurs when the car is in gear. In neutral you can rev the nuts off it.
You're at a standstill, say at a red light. The light goes green and you put it in D (or 3, or 2), release the handbrake and squeeze the throttle. Instead of the revs rising and the car moving forwards the revs don't rise - if anything they drop slightly, and the car won't move. It doesn't seem to matter how much throttle you give it.
Eventually it decides that it wants to accelerate but it gains speed and revs much slower than it should. At some point once you're moving, it decides that its at a good enough speed (somewhere between 20mph and 30?) to function properly.

If you start it in 2 then it will start in 1st gear and the problem is much shorter-lived than if it starts in 2nd. It's still hesitant but is much more willing to rev.

 

[jonnyboy]

Take it back to the people who just relieved you of £800 would be my first suggestion !!!!!!
Did they not road test it????????

 

[carat 3.6]

Where in London are you?

 

[BlueQuinn]

Bethnal Green

 

[carat 3.6]

I'm trying to think of someone near you that knows the bosch cis system. What did the garage you used say about the problem persisting?

 

[BlueQuinn]

It manifested itself on the way home from the garage. I'll have to ring them tomorrow. I'm not wild about the prospect of throwing yet more money at loads of diagnostics.

I was wondering about any tests I can do to eliminate various things - e.g. Disconnect or short the EHA valve

 

[jonnyboy]

I presume you have discounted it being an HT fault, bearing in mind it is occurring under load but not while revving in neutral/park?

 

[BlueQuinn]

I haven't discounted anything yet, but that's because I don't know what to discount.
If it was an HT problem, would it also occur in neutral?

Can I discount anything (fuel pump, EHA valve, OVP, FPR, dizzy) on the basis of:
1. it starts and idles fine.
2. there doesn't seem to be a problem unless it's in gear.
3. It has just had a new inlet air temperature sensor.

 

[carat 3.6]

When was the distributor cap and rotor arm last changed?

It isnt the fuel pump, or ovp relay.

 

[jonnyboy]

Seen plenty of HT faults over the years that only present when the engine is under load - ie driven/attempted acceleration, yet all seems well when idling/revved in park/neutral.

I have a real concern from your thread relating to who touched the car for you this week?

 

[carat 3.6]

I have a real concern from your thread relating to who touched the car for you this week?

I'll second that.

 

[BlueQuinn]

Whilst there is a 6 year hole in its history from 2006-2012 the last documented change of rotor arm was 15 Dec 1997 at 143,607 miles.

I'm not going to name and shame the garage just yet because I haven't had a chance to talk to them about it. Unfortunately late last night my wife was rushed into hospital, so the car will have to wait.