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  #1  
Old 08-19-2016, 10:19 PM
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Question 190E low power

Since I bought it 2 mos ago, my 1990 190E 2.6 with 77k miles is low on power off the line. 0-60 is 15 sec vs expected 9 sec. It also starts hard and idles slow and rough for a couple minutes. After that, except for the low power, it runs very smooth--no stumbling or missing. Here is what I know:

System and lower chamber fuel pressures are in spec-5.3 bar system with lower chamber 0.4 bar less.
Accumulator is new--holds 40 psi system pressure for hours after shut down (meets spec). Old one was bad, and the new one helped cold starting a lot.
O2 sensor was bad and I replaced it. Old one would not go above 1V even when heated to cherry red. New one did not help performance though.
EHA coil resistance is in spec. Disconnecting it makes no difference.
Temp sensor is good. Resistance is correct. Disconnecting it makes no difference.
Plugs are new Bosch copper. Old NGK plugs were clean and looked like they were running lean. All plug wires look very good.
Compression is 180+/-5 psi on all cylinders

Big mystery is that the CIS-E runs in open loop at a constant 10% duty cycle (at pins 2 and 3 of diagnostic port), and O2 sensor voltage drops from initial 4.5V down to under 0.1 V after it warms up. This all says LEAN which makes low power and acceleration make sense. Gas mileage is good. There is no detonation/knock. I am considering adjusting the mixture screw, but not until after I can get it to run in closed loop with fluctuating duty cycle and O2 sensor voltage. I haven't checked ignition timing/dwell. Any ideas??

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  #2  
Old 08-20-2016, 01:13 AM
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I don't have anything too valuable to offer. Make sure the dist cap is good and clean. I suppose the fuel filter could be partially clogged. It would not affect the pressure at idle. I assume the fuel is fresh. Lean might indicate an air leak and that would go along with old hoses, etc. You could try a smoke test I suppose. You don't want to run lean and burn a valve.
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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra
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  #3  
Old 08-20-2016, 12:20 PM
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It sounds like the "E" part of the CIS-E system is not functioning. One reason for hard starting is that the E-part of the system has all the cold start enhancements.

The overvoltage protection relay is often a culprit as it supplies power to the ECU and also the ABS controller, so a bad OVP relay will usually cause the ABS warning light to be illuminated.

When you turn on the ignition, check that the ABS light comes on. If not, the bulb may be burned out or removed. Check that the fuse(s) on the top of OVP relay are okay.

If you can borrow a known good OVP relay, install it and see if the problems go away.

Duke
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  #4  
Old 08-25-2016, 10:09 PM
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Location: St Paul, MN
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190E low power

Got a new OVP relay and installed it with no luck. The one in it looks really new (genuine MB part), so now I have a spare OVP relay . I rechecked the voltage at the throttle linkage microswitch with ignition on and it checked out right at 12V (I had read zero in an earlier test, which is what led me to buy the new OVP. I must have made a mistake last time I checked it.). I'm starting to suspect the ECU is bad. I don't think it really controls anything other than the AF ratio. Will the car run with a dead ECU?
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  #5  
Old 08-25-2016, 11:12 PM
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Look up the code for a constant 10% "duty cycle" signal - this is the ECU is giving an error code

If you are measuring this 10% reading with a modern DVM then you probably have to flip the value if you haven't already (to 90%)
__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #6  
Old 08-30-2016, 01:37 PM
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Quote:
Originally Posted by haasej2 View Post
Will the car run with a dead ECU?
Yes, if the OVP is faulty, no power to the ECU, but the engine will operate.

Mercedes claimed that the KE system will function even if the electronics fail. That's true, but they neglected to state that all the cold start enhancements are in the electronics, so if the ECU is inoperative the car will be hard to cold start.

Remove the big ECU connector and carefully check it for bent pins/receptacles, corrosion etc. If it checks out give both the pins and receptacles a shot of electrical contact cleaner, reinstall carefully and securely and see if that helps.

If any KE ECU failures have been reported here, they must be rare, but connector problems on 25 year old cars are common.

Duke
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  #7  
Old 08-31-2016, 11:15 PM
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Blown ECU

Well, things are NOT going my way. I'm aware that my 10% DVM reading is equivalent to MB 90%. Their shop manual says "unused--no fault code" for a 90% reading. I got my new ebay ECU today and hooked it up. The initial signs were great. Had current at EHA that was in spec (around 13 mv cold I think). It started up much better and came up to idle for a minute or so, then reverted to old low idle. I had the O2 sensor disconnected, so figured that was the issue (I understand the engine runs open loop for a short time after startup). Shut car off, reconnected sensor, started and was back to the old "normal". Then checked EHA current again and it was zero. Voltage at air sensor was essentially zero too vs spec of 5V. Put old ECU back in and now the air sensor is at 5V regardless of sensor position. I think it is blown. One thing that could have been a factor in all this is that I started the car using a remote battery. It was out of the car and I used jumper cables to connect to the battery cables. It cranked very slowly and stopped cranking a few times like when your battery is almost dead. Could this damage the ECU or other electronics? If so, some engineer at MB should have been fired! I did NOT reverse the battery cables at any time. I rechecked the OVP relay. I'll be returning the ECU and hope my air sensor isn't blown. BTW, I did the circuit board cleaner on my old ECU with no effect. It was replaced in 1999 if that is any clue. The 190E is a really nice car, but I bought it to DRIVE, not to work on for 100s of hours! I'll be checking the wiring harness (again) but my big question is will low voltage on cranking damage the ECU or air sensor?
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  #8  
Old 09-01-2016, 01:11 AM
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The air flow sensor needs to have the correct power going to it - the power supplied is measured between the top and the bottom pins. This should be available with the ignition switched on and the engine stopped.

(I'm not quoting voltages because they can be different - check in the FSM)

#########

I had a similarly frustrating time with my W201 a trick (that is tedious and laborious) is to go through the specifications from the FSM and measure each sensor and actuator but to also do this at the plug for the ECU


#########

As for the "I might have damaged it when I jump started it" - these systems are good quality - they might seem otherwise because they are frustrating little bastards (!) - but it is probably best to remove that thought from your head. Banish the "what if" and replace it with "well that's measured and OK".

Facts help with CIS trauma!
__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #9  
Old 09-09-2016, 08:29 PM
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190E low power progress--what is normal?

Well, I got a different used ECU and VERY CAREFULLY installed it, also checking voltage on airflow sensor potentiometer (in spec), current to EHA (slightly below spec cold but car was slightly warmer than 20C test point). Started car and came up to a smooth idle right away and runs very well. Drove it around tonight with my DVM hooked up to the test points #2 and 3 on the diagnostic port. On initial startup duty cycle was reading a steady 50% (I think this is normal as the system starts out in open loop), then after a minute or so duty cycle started oscillating. The range was mainly in the 60-70% range, with some values jumping beyond that. Occasionally it would hold at 50% for a second or 2 and then start oscillating again. On the freeway the car seems to have great power (for a 1990s luxury car). Give it a lot of gas at 60mph (3000 rpm) and it will kick down and accelerate fast and smooth to 5000 rpm (when I backed off to avoid a ticket). It seems to be ok from a standing start too. Runs smooth as silk. Now for my question--WHAT IS NORMAL POWER? I've seen on the 0-60.com website that the 190E did 0-60 in under 9 sec, but it doesn't specify whether it was a manual or auto. I watched a utube video of a 190E doing 0-60 in under 9 sec, but it sounded like a manual with a good driver. Before I fixed the ECU mine was doing 0-60 in around 15 sec, with the main issue being low rpm power off the line. Now it does 0-60 in 12 sec, with better power off the line but nothing great. What experience do you have with your 190E 2.6 times from 0-60? I have tested the throttle position switch resistances and they are ok. Is there some type of fuel enrichment at full throttle that isn't working right? I'm planning on taking the car to a transmission shop and get it adjusted for smoother shifting, but don't want to do it until I am sure the engine is running right.
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  #10  
Old 09-10-2016, 04:20 AM
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Join Date: Sep 2009
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Um I think there's something in the user manual about performance and fuel consumption. If you don't have a book in your glove box any more there's a copy on the startek site I think.
__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #11  
Old 09-25-2016, 08:00 PM
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Location: St Paul, MN
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Car continues to run great. I discovered the kickdown switch that shifts down when you push harder on the accelerator pedal and that has lowered my 0-60 times to around 10.4 sec. Probably will do better but it is hard to find a good place to test it. The transmission shifts kind of abruptly and I am planning to have that looked into. It might help. If I can get down under 10 sec I will consider the car to be "healthy".
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  #12  
Old 09-29-2016, 12:58 PM
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Quote:
Originally Posted by haasej2 View Post
Now for my question--WHAT IS NORMAL POWER? I've seen on the 0-60.com website that the 190E did 0-60 in under 9 sec, but it doesn't specify whether it was a manual or auto. I watched a utube video of a 190E doing 0-60 in under 9 sec, but it sounded like a manual with a good driver.
I had both a chassis dyno test and ran my 190E 2.6 five-speed on a drag strip several times. SAE corrected RWHP is about 135, which jibes with the SAE net crankshaft rating of 158 assuming 0.85 drivetrain/tire efficiency.

The biggest problem with 0-60 is traction due to the 57 percent front weight bias and open differential. I recall the 60' times were a bog slow 2.5+ seconds compared to 2.2 for my '91 MR2 with the 130 HP Camry engine, so 0-60 in about nine is realistic. It could be a lot closer to 8 with a LSD. ETs wera about 17 flat with a trap speed of 86, which is high for that ET. Again, it was a traction issue at the starting line. The MR2 was 16.6 at about 82, which reflects its excellent hookup at the starting line.

I have achieved 134 MPH on a level road and the acceleration from 70-90 in third gear is impressive. The 2.6 is certainly much faster than my previous '84 2.3!

One issue is the lazy spark advance map. Removing the R16/1 resistor will make it more aggressive and improve low end torque, which may be more of an issue with a manual since the converter will always achieve stall speed of about 2000 with significant throttle application. Prior to removing the R16/1 fifth was not useable below about 45 MPH. Now I can drop it in to fifth at about 35 (about 1500 revs) and don't have to downshift to accelerate moderately.

I short the R16/1 for emission testing to retard the spark advance map, which allows passing the ASM test with greater margin, but there is litterally no power below about 2000.

The R16/1 pigtail on the 190E 2.6 is tied to the plastic shield on the inside side of the battery compartment. Do a search to find out more about the R16/1.

Duke

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