1987 190E 2.3 - Poor acceleration and pathetic top speed
 

Hi all -- Long time lurker, first time poster. Please be kind!

We've got a nice little burgundy Baby Benz that's been a reliable work car for me for about 10 years now. A few years ago we had the heater core puke and we replaced that (golly, fun job, but we followed a post here with photos that was a huge help), and we've also done some other (more minor) repairs over the years including a new fuel pump and mass airflow sensor.

About a year ago we started noticing it was becoming sort of sluggish, the problem progressed to the point that now it's got horrible acceleration and top speed is sometimes as slow as 45-50 mph.

It starts fine and idles perfectly.

The engine doesn't have any bucking or hesitation, it just acts like a big car with a really small engine - no torque, no horsepower.

It is running rich - exhaust smell is very "fuel-ey".

Sometimes I can baby it up to a higher speed by backing off on the throttle a bit, then sometimes it'll get going better if I do the opposite and keep it pinned and force it to stay in a lower gear for longer before shifting (automatic).

It doesn't seem to be affected by temperature, although it does seem to be most apparent when it's cold, and has better acceleration and top speed the longer it's been running.

It's so weird, some days it's all I can do to eek out 55 mph on the flats, and other days it'll sing along at 75 over the same tarmac.

Even when it is running its best, hills will still slow it considerably.

As mentioned, we've replaced the mass airflow sensor, the distributor cap and spark plug wires, and of course installed new spark plugs. Old plugs all looked good, none showed that any one cylinder was running any differently than its brothers.

We also checked the gas line pressure with the proper gauges (loaned to us by a Mercedes mechanic) and that all checked out great.

Thanks for any help!

Forgot to add - we've tried fuel injector cleaner a few times, which results in no changes.

No ideas?

I dont have an answer for you but maybe if you post this issue on 190Rev.net you'll get an answer.

There is a fuel pressure regulator that runs off vacuum from the breather hose located on the side of the valve cover. Remove the air box and check the vacuum lines for oil in them and check the breather hose as well. The icv and fuel pressure regulator are controlled by the vacuum from the valve cover.

Obviously also check for vacuum leaks lol. Best of luck, let us know what you find.

Loss of acceleration or power (torque) sometimes means a bad cam (camshaft position) sensor. I've had that issue with my older cars. Check it out, it may need to be replaced.

190e does not have a cam sensor. It does have a crank sensor and it will not turn over with a bad one. And if it does it will run in limp mode and set a check engine light.

Thanks so much for the tip! I'm sorry it took so long for me to come back to this, I thought I had this set up to get email notifications but I guess not!

We do have oil in the lines going into the fuel pressure regulator. Also the breather tube has fallen out a few times and we've stuck it back in (I assume the small tube out the left side of the unit is the breather).

So, if there's oil in these lines and we clean them out, what keeps them from just loading back up with oil? I'm thinking this would have something to do with leaky valve seals which is causing oil from the head to blow back through this vacuum system?

The "blow by" oil is supposed to be routed to the air cleaner box, but if it's excessive, it will tend to pool in the box or in the valve cover area.

Take the time to check the compression in the bores and possibly a leak down test, since it could be the piston rings, but more likely the valve seals. Anyway, it's always a good idea to know if your getting even and strong compression throughout.

It doesn't burn any oil, even on startup after sitting a week or more, but I will do a compression check. I'm wondering if most of our issues are from that air tube disengaging with some frequency.

Went ahead and ordered a new pressure regulator from eBay for cheap, says it's OEM NOS from Germany, we'll see. It was worth $45 to check because if this isn't the culprit I'm afraid this car is destined for the scrap yard, which would be very sad, she's physically in such good shape.

You won't see smoke from the tailpipe if it's blow-by since it doesn't get into the combustion chamber and sent out the tailpipe. It happens on the compression stroke of the piston, when both intake and exhaust valves are supposed to be closed. If the pressure from the cylinder leaks past the valve face and seals, it will pressurize the area under the valve cover. The valve cover has a flat baffle that's attached to the top that's supposed to catch oil, but if the pressure is high, vaporized oil can be sent through the tube that's attached to the baffle and routes to the air cleaner housing.

The 2.3 is known for the oil in those lines, under the valve cover there is an oil separator baffle. On older motors it's replaceable and made of metal, on the 90-93 they are plastic and not sold individually and only with the whole valve cover. If clearing that vacuum lines to the regulator sees symptoms improve, then order a new separator from the dealer as it will come with a new gasket for the baffle since yours is an older single sprocket timing chain motor and the part is replaceable. You will need to replace the valve cover gasket on the way back out so have one handy as well.

I actually bought a 1987 motor just for the valve cover and baffle as mine was having similar problems and mine is a 1991 with the plastic baffle which was cracked and broken. New cover from the dealer was 561$, whole motor used was $200. Problem solved and I now have the metal baffle as a kicker.

I just reread that your breather fell off, if it's loose enough to just fall off you found your vacuum leaks. Replace that breather assembly!

Does the car have a catalytic converter? Any possibility it could be loaded up and obstructing the exhaust flow?

bad over voltage relay. maybe even just a fuse. mine did the same.

When was the last time the fuel filter was replaced? and/or injectors?

Did you ever figure this out? I was watching the videos on YouTube of mercedessource and mine is acting similarly and i suspect it may be the seals on the injectors....

unbolt the front pipe from the exhaust manifold and run it. if that fixes it, you have a plugged cat. my 87 190e huffs some oil up through the breather onto the air cleaner and it runs just fine. i think the oil thing is typical. its not a great PCV/breather system. if the cat is plugged, mebe she's running rich. replace the oxygen sensor if you already checked fuel pressure. of course the plugs should've been dark if that was the case... lets not get ahead of ourselves. check the cat

fuel pump, catalytic converter..

cat is clogged engine can't exhale. This was my first thought.

I had the same issue in my 86’. DocWallas comment was where I found my issue.The old plastic vacuum hose attached to the side of the valve cover was split about 1/2 inch. Corrected this issue and a great deal of power was restored.

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I had the same issue in my 86’. DocWallas comment was where I found my issue.The old plastic vacuum hose attached to the side of the valve cover was split about 1/2 inch. Corrected this issue and a great deal of power was restored.