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Old 12-09-2003, 12:04 AM
Posts: n/a
Unhappy 190E running rich problem AGAIN after repair!!!HELP!!!

Only been 2 months since I swapped out my fuel distributor to solve a problem of running rich.

Old problem seems to have cropped up again!NO!!!

Instead of a gradually deteriorating fuel mileage over a period of weeks like the last time, my fuel mileage went bad overnight!

When I last filled up my tank on Friday evening, the car had done close to 400km and needed 44 litres so gas mileage was about 9km/litre.My fuel mileage has been consistently around this figure since I swapped out my old FD for a used one.

By Saturday afternoon, having only driven for 50km, the fuel indicator was at the 3/4 mark!

I thought there may be a fault in the sender but in any case I decided to monitor the situation closely.

No clouds of black smoke on acceleration, no severe hestation on acceleration, etc at this point in time.

Checked the car for leaks but could not find any.

On Saturday evening, I noticed that when warm, there was a severe hesitation accelerating from standstill (a/c is on as always).Flooding maybe???

With the a/c off, the hesitation was gone.Looked at the exhaust and saw light black smoke at idle.When driving, I don't see any clouds of black smoke behind me like before.Maybe there is but I'm not seeing it...

Now as I type this message, the car has done 170km since the fill-up on Friday and the tank is almost at the 1/4 mark!

Seems that car runs rich, but performs better when cold.When warm, rough idle, severe hesitation on acceleration (like flooding).Fuel mileage is very bad.

Looks like I'm gonna have to check out the car again but I wonder what would cause the fuel mileage to go bad really quick?

I'll be damned if it's the fuel distributor that's foiled AGAIN!

This issue is frustrating me!!!

On a side note, after replacing the FD, when cold, the car would always fire when started, then die.On second try, the idle would be lumpy for a few seconds and then catch - then idle would be normal.I read on a few posts that this points to a failing fuel pressure regulator.

I also wonder if this is at all related to the current problem.

Car also had an oil/filter/plugs change on Saturday.Wonder if those service guys may have disconnected/touched something by accident (doubt it)?

I took the EHA off and the situation seemed no different - so we're dealing with a mechanical problem here AGAIN.

Took out my EHA wire harness and MM to look at the EHA current.

Key on, engine off - 4mA???????Something is wrong here.Normally it's 10mA.OVP?

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Old 12-09-2003, 02:47 AM
Posts: n/a
Both fuses of the OVP (updated version) are OK.

Air filter 2 months old.

Coolant temp sensor tested 280ohm at abt 85 deg C (to spec).

Key on engine off is 4mA.

Engine on, current is still at 4mA.

Something is wrong.
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Old 12-09-2003, 07:51 AM
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Having been around ALOT of used vehicles and known alot of DIY'ers that tend to buy used vehicles then 'fix' them, it is my opinion that some cars have been DIY until they CANNOT be fixed, and will never really run right. Too many little things being screwed with too many times.

Based on the history of your posts, your vehicle seems to be one of'em, get rid of it and get something else.
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Old 12-09-2003, 09:36 AM
Posts: n/a
Thanks for the words of encouragement, dude... hehe

Even my nephew's skateboard is appealing at this moment!
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Old 12-09-2003, 03:00 PM
sunil190e-1.8's Avatar
Registered User
Join Date: Jun 2002
Location: uk
Posts: 236

feel your frustration.

this board always provides laughs when you need them most!!

try spark plugs

ignition wire /end cap faulty


distributor cap

leaky injector.

look at your fuel injection component connectors ?loose

you could also look at the fault finding section in the haynes manual for 190e cars-usually they give you list of causes/possible repairs for execessive fuel consumption.

hope this helps.
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Old 12-09-2003, 03:45 PM
Posts: n/a
Just a thought:

It seems as if you are loosing A LOT of fuel, but the next time you have the car up on a lift, take a look at the fuel pumps. I was getting bad mileage on my 1988 190 E and when I had it up on a lift, I was looking around (making mental notes of what I want to up grade) and poking around (no rust!) and I noticed the little cup/cap/retainer that covers the fuel pumps was moist. The fuel pumps are by the rear axle, drivers (left) side and I think most 190s have two of them - in series, so to speak. When I pulled off the pump cover, it was full of fuel. I detected a crack on one of the fuel lines (the one between the stage one and stage two pump) and replacing that solved a number of problems I was having. I never noticed fuel on the ground. I think that was because the cover held so much. When I drove, it would spill out. When I stopped, and turned the motor off, there was no more leaking. That's why I never saw a puddle of fuel on the driveway. Anyway, it's just a thought, but you might look into it.
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Old 12-09-2003, 08:28 PM
Posts: n/a
Thanks for the tips, guys.

Plugs/wires/etc (ignition stuff have been done recently) except coil.

My car seems to run rich all the time but performance is good when cold.

When warm, there is hesitation on acceleration and idle becomes lumpy.

Disconnecting the EHA seems to have got me better mileage but need to drive further to be sure.

Fuel indicator was at 3/4 mark with only 50km on the tripmeter when I first noticed this problem on Saturday with the EHA on.

I topped up the tank and took off the EHA yesterday.

Today, having done 70km, the fuel indicator is still above the 3/4 mark.

Trex - I'm not losing fuel from a leak - performance is crappy and exhaust is smoking black (sign of a rich mixture).

Keep 'em coming guys.

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Old 12-10-2003, 03:01 AM
sunil190e-1.8's Avatar
Registered User
Join Date: Jun 2002
Location: uk
Posts: 236

two other things spring to mind

cold start valve fauty-ie continuing to spray in extra fuel when car is hot.

auxiliary air valve-sticking shut even though car is hot-o2 starvation
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Old 12-10-2003, 08:52 PM
Posts: n/a

I unplugged the cold start valve connector which has not made a difference.I have yet to check (which I did the last time) if the valve is leaking.

auxiliary air valve-sticking shut even though car is hot-o2 starvation
Is this the rotary idle valve, the tubular thing that's connected at the end of the breather hose from the valve cover/airfilter housing near the intake?

It may be possible coz when the car is warm, idle is lumpy, and idle speed drops (indicating less air?).There is a little fluctuation in idle.

Also, the oil pressure fluctuates between 2 and 1.8 with the idle.

Normally, after an oil change (last Saturday), the oil pressure is around 2.5 at warm idle.

Prior to the oil change, oil pressure was between 2.2 and 2, which I use as a service indicator (the drop in oil pressure closer to 2 in my car normally coincides with the 10000km oil change).

As a matter of fact, a week before this problem, I noticed slightly surging idle speed when decelerating.

Don't know for sure if these symptoms are related to the idle valve unless someone else has had similar issues and can advise.

I will check and clean (with carb cleaner?) the valve and update.

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Old 12-10-2003, 11:27 PM
Join Date: Feb 2000
Location: seattle, wa
Posts: 87
I can't remember if you said that you've checked your thermo switch for the fuelinjection. Should be a four hole plug at the left rear of the head. I've had extreme rich running a few times after disturbing this during cylinder head removal.
Paul Roberts
Mercedes Centrum Inc.
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Old 12-10-2003, 11:38 PM
Posts: n/a

If it's th e4-pin coolant temp sensor, yep, i checked the reistance on the diagonally opposite pins and they measure around 280ohms at abt 85 deg C, so it's good.

However, the problem does seem temp-related.

I think my car is running rich cold or warm.

However, it runs well when cold (with a/c on even).

When warm, I need to turn off the a/c to get the car moving from a stop.even then, some hesitation before the car accelerates.

Black smoke and strong exhaust smell obviously from running rich.

This syndrome of running rich happened overnight after an oil change.They didn't adjust the mixture or anything but I wonder if they accidentally knocked off/disconnected something.

I have read on other posts that there is a vacuum advance hose on the distributor that if disconnected, causes the car to run rich (if I remember correctly).I will look for this vac hose but wonder if anyone knows if this is true?

Thanks for your thoughts, Paul.
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Old 12-11-2003, 11:04 PM
Cigar Havana's Avatar
Registered User
Join Date: Jan 2003
Location: Toronto Canada
Posts: 378
o2 Sensor

Did you check the o2 sensor? If it has failed, I believe it will default to a rich mixture.
1989 420 SEL
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Old 12-11-2003, 11:55 PM
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I don't have an O2 sensor on the car (checked the entire exhaust - it's original).

Even if the car had one and it was faulty, it would have been bypassed coz I have disconnected the EHA, but still mixture is too rich.

Leaned the mixture by 1/4 turn - still rich with EHA off.

Idle and running is good when cold but once engine gets warm, feels like it's flooding - rough lumpy idle and severe hesitation on acceleration.

Fuel pressure regulator is suspect - my old one was leaking fuel, and I swapped it out with a used one at the same time as my fuel distributor.


Need some help to check fuel pressure...

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Old 12-12-2003, 01:13 AM
Posts: n/a

Symptoms are as follows :

Car running rich, blowing black smoke, bad fuel mileage.

When cold, car runs well blowing black smoke lightly.

When warm, idle is lumpy and drops to about 600rpm.Hesitating severly on acceleration and blowing lots of black smoke.

Symptoms are the same with the EHA on or off.

Had a similar problem, same symptoms and solved it about 2 months ago by replacing used fuel distributor and fuel pressure regulator.

Background on last repair :

Same symptoms as above.

Swapped out FPR with a used one.

Car ran fine on the highway for 20 minutes and then suddenly back to rich running.

Swapped out FD and also FPR again (both used units).

Problem solved.

Don't think the fuel distributor has gone bad, looks like a screwy fuel pressure regulator.May have been the FPR all along but don't know for sure coz both the FD and FPR were swapped at the same time.

I can see traces of fuel leaking from the nipple of the vent hose on the FPR that is now in the car.

If I understand correctly, a bad fuel pressure regulator can have an effect on fuel delivery (fuel mileage) - rich running condition.

Another interesting symptom was that after I had the FD and FPR swapped (the old FPR was leaking fuel), the car had a slight problem with cold starts.

1st key, it fires and then dies.

2nd key, it fires, lumpy idle for 3 to 4 seconds, then catches and idles fine.

The new used one is now also leaking fuel, though I did not check if it was leaking when I first swapped it in 2 months ago.

Maybe, swapping out the FD the last time was unnecessary...

Meanwhile, in Gotham City...
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Old 12-12-2003, 05:25 AM
Registered User
Join Date: Sep 2003
Location: France
Posts: 487
you are facing a difficult situation

I would try the followings.

Is there any loss of power? Are the compression in cylinders OK?

How look your plugs? Is there ignition?

Is there any fuel flowing from vaccum line to hose valve cover to air filter?

With motor off does it stronlgy smell fuel in the airflow meter
in normal way fuel goes to injector only to my opinion there two locations for a leak on the bottom part of the fuel distributor or the membran of the fuel pressure regulator (no smell should be in the air flowmeter)?

good luck
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