I've recently overhauled the top end of the engine compartment of my 1990 190e 2.6. I picked it up as a project car. It was barely running and smoking when I bought it, but the body and interior are in great shape. I've been restoring it's mechanical condition. I started with a valve job, which went rather well. It had a cracked valve and lot's of "I don't change my oil" sludge build up. I have close to 10k miles on the rebuild now and some things are still lingering. I replaced the timing chain and cam gear while I had it all apart and am not entirely certain that I installed them correctly.

I don't know how this car is supposed to run as I have not driven one that is running properly. However, since I put this scrap heap back in to the likings of a vehicle, it has started poorly. It starts, jumps up to 1500 rpm then bucks and kicks at 500 rpm for a few seconds then smoothes right out. Obviously this is not an internal engine issue, so I have been living with it for some time. Under heavy acceleration and higher RPM it runs very smooth, but I can tell it's lacking it's potential power.

I replaced the fuel pressure regulator and the fuel pumps & filter and adjusted the mixture for optimum results.

I know there's a cold start valve, but am not sure how to check if it's working.

I'm starting to think I may have put the timing chain together one tooth off. When I shut the engine off, the slack of the timing chain is on the drivers side opposite of the tensioner. I didn't note which side had slack when I originally disassembled it.

Also note: I am suffering with really slow acceleration when the AC is on. With the accelerator to the floor, I can count to 4 sometimes 5 before hitting 10 miles per hour in heavy summer traffic.

Is there an easy way to check the timing chain installation and the cold start valve?

Thanks!

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1990 190e 2.6 (About to have a Kompressor )

One of the things I've learned the hard way is not to assume that there's only one problem - especially when the symptoms are a little murky as yours seem to be. I think I would replace the injectors - unless you know them to be good. Bad injectors are a common cause of rough starts - and the injectors on that car are relatively inexpensive and easy to replace. But even if they're bad I would doubt it's your only problem.

just went through this on a 2.3. If you pull the valve cover off and set #1 piston to TDC on the compression stroke, you will see a line cast into the cam behind the cam sprocket. This should line up with the deck of the cylinder head. If not your chain is stretched or you're out by a notch. I pinned my rattle down to a bad tensioner dampener and alternator bearing.

You may have a fuel pressure leakdown, maybe a leaky EHA or fuel distributor - but the problems sound still more pronounced. Have you checked duty cycle on the diagnostic plug? Kinda sounds like you are in limp mode.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

Not sure about the duty cycle or how to check it properly.
I've read about an EHA adjustment. Am going to try that for now.

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1990 190e 2.6 (About to have a Kompressor )

Just as an added note;

When in park with AC off, it takes 3-4 seconds for the engine to rev up to 4,000 rpm with my foot to the floor or any combination there of. Slow push, fast push...

Throttle response is good after 3,000 RPM.

Is this normal?

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1990 190e 2.6 (About to have a Kompressor )

Have you checked the Intake Boot between the Aif Flow Meter and the actual throttle Body! They tend to crack and suck in air bypassing the AFM, of course not giving enough fuel then? Have you cleaned the Idle Air Control Valve and checked all the rubber hoses associated with that? Next check all vacuum connections for leaks! And finally spray a ton of Carb Cleaner around and clean the throttle plate and AFM and IACV real good!

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....

I just cleaned an inspected all of the associated intake parts when I did the valve job. I also replaced all of the little specialty hoses in and around the intake. The boot is still the original.
Perhaps the intake boot it's leaking- that would make sense.

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1990 190e 2.6 (About to have a Kompressor )

I found my vacuum leak... It's in the AC system... I plugged the intake and wow. She actually runs decent. I was pleasantly surprised.

However when I turn the AC on, it's slow slow going again.

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1990 190e 2.6 (About to have a Kompressor )

AC Compressors put a serious drag on the motor! So yeah it is normal to slow it down somewhat. Really noticeable for me on my C230K cause that poor little 1.8 just can't spin it as easily as a V-6 or V-8 can! How much do you slow when the AC compressor kicks in?

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....

I read the following thread on adjusting the EHA and wow did it make a difference!

Adjusting an EHA. It IS possible!!

Running the AC unit running MAX out here in FL will up the temp to the 100+C range. When the temp is above ~85C and the AC is on the car is really really sluggish. So I hit the AC button just before a light turns green and she's OK. Not going to get me killed trying to vacate a busy intersection. (a vast improvement)

I replaced the Water Temp Sensor ($26 at the dealer) and to no avail it still starts rough, but smooths out within seconds. (as usual)

I'm interested to know more about setting the duty cycle.

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1990 190e 2.6 (About to have a Kompressor )