190E 16v with lumpy idle for the past 6 years - PeachParts Mercedes-Benz Forum

pentoman · #1 12-17-2011, 08:59 AM

Hi all, my 190E 16v runs with a lumpy idle at around 1000rpm. It has always done this and I've owned it for 6 years. It doesn't exhibit any other major problems - e.g. it produces good power, it doesn't stall, it starts as well as a 20 year old car should. The only thing abnormal is that it seems to need a new distributor cap every couple of years.

During the 6 years I have owned it, it has always had this lumpy idle. It's an irregular misfire. It's quite subtle, and you mostly just feel it as a shaking of the car. It goes away when you increase the revs to 1300+. I have compared with another 16v which didn't exhibit the same misfire, it ran more smoothly.

During my ownership, some of the ignition parts have been replaced. E.g. It has had new plugs (the recommended ones), and it has been through about 3 or 4 distributor rotos and caps. I even have a spare ignition ECU which I tried, it makes no difference. The plug leads and the coil have not been changed because they are more expensive. I did once have the spark tested by a mechanic - it had a really strong spark.

On the fuel system, in my ownership the fuel filter was replaced, the injectors were replaced with brand new ones, And I have tried replacing the whole fuel metering setup with a spare that I purchased from another car of the same year. None of this made a noticeable difference.

On the air system, I just replaced the main air pipes for the PCV, the IACV, and the ones to the injectors, with brand new pipes (actually I have one more still left to do). My gauge reads 15in of vacuum, at idle.

The top-end of the engine has even been rebuilt with new valves etc and, still the stumble at idle remains exactly as it did before. An irregular stumble that you feel through the seat of your pants.

So, what have I missed and what else can I check? What can I investigate to give me some clues as to the cause of the problem? Could this be purely a characteristic which I will have to live with? It's not major, but I am curious to see what causes it and how it has persevered for so long.

JohnM. · #2 12-17-2011, 03:38 PM

Neglecting the plug wires is usually a bad idea. CIS Benz's have picky ignition systems. The wires can look OK on the outside and be HOSED on the inside. Very well could be why you are burning through caps/rotors.....

POS · #3 12-17-2011, 04:36 PM

Motor mounts only last a few years as well; that'll shake a car at idle.

pentoman · #4 12-21-2011, 01:55 PM

Thanks, so to repot back:

Motor mounts are new.
I will consider the leads. Is a resistance test with a meter satisfactory for seeing if wires are okay? Or any other test?

benhogan · #5 12-21-2011, 02:10 PM

you have a 2.5-16?

i didn't know there was such a thing.

on this side of the pond , it is a 2.3-16.

are the 190e 2.5-16 pretty rare in the UK?

POS · #6 12-21-2011, 10:26 PM

The 2.5-16 was a euro-only car that replaced the 2.3-16 in 1988. They're more rare than the 2.3-16, but I don't know the production figures of the 2.5-16.

Mercedes 190E 2.3-16

pentoman · #7 12-30-2011, 06:53 AM

Hello

On our side of the pond we have a 2.3-16 and 2.5-16. The 2.3 was replaced with the 2.5 in 1988. They are more or less identical apart from increased stroke (I think, this is from memory) of the 2.5 engine and other minor differences of compression ratio etc. The performance is a little better, with the 0-60mph time of the 2.3 being 8.0 and 0-60 of the 2.5 being 7.2 seconds. The top speeds are 3mph higher on the 2.5. Those speeds come from the same reliable magazine so are comparable. They made about 20,000 2.3 cars and 5000 2.5 cars. The 2.5 however is newer so is about equally as common as the 2.3, just due to age. Both are rare, though. I see maybe 1 per year, apart from at club meets.

The UK in particular really likes these cars and many people here know what they are. I get asked about it quite often when I'm driving it. In the UK useable performance cars with good cornering have always been much more popular than other countries. In addition the engine is designed by a famous British firm, so that helps our appreciation.

AlexHasA300SEL · #8 06-27-2015, 11:55 AM

I realize looking at your other posts that you sold the car mentio ed in this thread but out of curiousity (as i seam to have the exact same issue with my 2.3-16) i wanted to ask if you ever found the fix to that issue? Did you ever find out why you had the slight misfire/lumpy idle? Did you end up replacing the plug wires?

Your reply would be greatly appreciated, thank you.

-Alex