1984 190e 2.3 higher than normal idle when warm - PeachParts Mercedes-Benz Forum

geoff.doctor · #1 03-25-2009, 08:07 PM

OK guys, thanks for all the help so far, slowly but surely I am turning this benz into a roadworthy car.

The latest issue I am tackling is a slightly high (1100 rpm) warm idle. When I start the car it will idle right around 800 rpms. Once the engine warms up I cannot get the thing below 1100 (in neutral, its a 5spd manual so I can't tell you what it is in drive

Oil pressure and rpm gauge both fluctuate when warm, I have done some searching that led me to think it was the OVP, but after re-soldering the joints (which looked fine) and replacing the fuse the problem remains the same. Tried spraying carb cleaner around the intake and at vac connections and idle remained the same.

Unlike many other members on the board suffering from 2.3 idle issues, my car:

1. Always starts after the first few cranks fine, warm or cold
2. Never hesitates upon acceleration and has plenty of power
3. Has yet to stall out on me

A few other things that may be related, just took it for a 40 mile highway drive today, and after exiting the highway, it almost stalled, but revived it self after I gave it some gas. This is the same problem my Olds 88 had and it was corrected by replacing the Crankshaft Position Sensor, is that a part known to cause these problems on the 190?

Occasionally I smell gas while idling, like it is running rich but it always goes away when I am driving. Would a cold start injector always running cause a rich mixture at idle?

Any advice/ideas/thoughts are appreciated. I have read many different posts in this form regarding idle issues, and none seem to be quite like the one I am having. Hoping it's something simple before I go and buy a multimeter and begin testing individual components.

mbdoc · #2 03-26-2009, 08:00 AM

Have you tried adjusting the idle control screw on the idle valve?

geoff.doctor · #3 03-26-2009, 01:01 PM

I have not because I read that should not be played with, as it is normally another problem. I will give it a try

geoff.doctor · #4 03-26-2009, 02:34 PM

Few more tidbits of information, I decided to play around with unplugging a few components. When the 02 sensor is unplugged, the idle drops to the 800 range but surges terrible, almost stalling at time. Once plugged back in it returns with minimum surging back to 1100 rpms.

When I unplugged the OVP with the 02 sensor plugged in, the car's idle speed increased to about 1300 rpms. When plugging it back in the car almost died out, then revived itself and continued to run around 1100 rpms.

The car was just sitting idling so the temp started to rise. Righ around 100 degrees the fans kicked in, and it was about time for me to leave to go back to work. As I was pulling out of the parking lot I was in, the RPMs were at 800 and the car was running smooth! After it cooled down a bit and I got back to the office and it was right back at 1100! Damn though I got lucky!!

Sound like anything inparticular? I plan on buying a multimeter this weekend if I can't figure it out.

mak · #5 03-26-2009, 07:01 PM

around this time the temp sensors start to go haywire . i would replace this for starters . suggest ,clean the very bottom of the air flow unit . Normally the accumalation there causes idle variations. ICV

mak

professor · #6 03-26-2009, 09:53 PM

Did the 84 model have an ICV?

geoff.doctor · #7 03-27-2009, 09:41 AM

is the ICV a small cylindrical object with a connector and vac hose going into it located under the airbox?

professor · #8 03-27-2009, 03:27 PM

Quote:

Originally Posted by geoff.doctor

is the ICV a small cylindrical object with a connector and vac hose going into it located under the airbox?

sounds like it

geoff.doctor · #9 03-29-2009, 12:38 AM

Still not fixed!

Took of the ICV, cleaned it with alcohol and reinstalled it as it was pretty dirty inside. Also used some carb cleaner and cleaned up the throttle body. Everything seems to close as it should. Also took the EHA off, and I noticed someone as removed and reinstalled the brass screw that is visible once it is removed from the motor. If someone had adjusted the little 2mm hex, could that possible cause my problem?

Also noticed that the brass bearing is no longer in the lambda tower, so someone has obviously fooled around with the air/fuel mixture. After this discovery I went and bought a sears 82139 multimeter and tested the duty cycle. My car is an 84 190e 2.3 so I dont think I need to put it in diagnostic mode. The duty cycle reading would fluctuate from 0.0% to 18.5%-18.8% every few seconds. It did this from when it started to the time I turned it off after it reached 100 degrees. Is this fluctuation normal or is this an indicator that there is a faulty component? Duty cycle is suppose to be 45-50%, so the air/fuel may need to be adjusted but I just don't know if I can trust that duty cycle measure jumping around like that.

Any ideas?

Also grabbed a unadjusted EHA off a 87 2.3, It know they made some changes to the 2.3L after 87, but the part looks identical. Anyone know if this will work on an 84? Cant get on to EPCnet to check part number because of this damn MacBook.

professor · #10 03-29-2009, 12:11 PM

Try this link
1988 190E 2.3 stalling

geoff.doctor · #11 03-29-2009, 09:45 PM

Well I decided since I was not getting results checking the duty cycle I would check the voltage between pins 3 and 2, it stayed right around 0.64 - 0.65! Then decided to check 02 voltage warm (since the car was already warm), and its putting out just over 0.9V! Turned it off for awhile started it back up and it was at .899. I will try it again tomorrow when the engine is cold. If I check the voltage between pins 3 and 2 with the O2 unplugged it right around .4 So either the system is running really really really rich (thought these only went from .02-.08) Or my O2 is faulty, what do you think?

I am going to hold off adjusting the air/fuel screw until I get an accurate duty cycle reading. I noticed my alternator is not putting out as much juice as it should, it's only maintaining 11.7 volts. Guess its time for a new alternator or voltage regulator. After I get the charging system back to what it should be I will go ahead and retest the O2 and duty cycle.

professor · #12 03-29-2009, 10:20 PM

Quote:

Originally Posted by geoff.doctor

Well I decided since I was not getting results checking the duty cycle I would check the voltage between pins 3 and 2, it stayed right around 0.64 - 0.65! Then decided to check 02 voltage warm (since the car was already warm), and its putting out just over 0.9V! Turned it off for awhile started it back up and it was at .899. I will try it again tomorrow when the engine is cold. If I check the voltage between pins 3 and 2 with the O2 unplugged it right around .4 So either the system is running really really really rich (thought these only went from .02-.08) Or my O2 is faulty, what do you think?

I am going to hold off adjusting the air/fuel screw until I get an accurate duty cycle reading. I noticed my alternator is not putting out as much juice as it should, it's only maintaining 11.7 volts. Guess its time for a new alternator or voltage regulator. After I get the charging system back to what it should be I will go ahead and retest the O2 and duty cycle.

Very prudent approach!

geoff.doctor · #13 03-30-2009, 06:42 PM

Well I got the new alternator on, solid 14V current now. Still couldnt read the duty cycle, so I check the voltage on the O2 and it was still showing .9V. I decided to adjust the air/fuel mixture and lean it out a little. Went too far as the O2 voltage went and stayed between 0 and 0.1. Went a little rich and got the 3-7 fluctuation at idle I was looking for. Hooked up pins 3 and 2 and I got a voltage reading!! Calculated the duty cycle and it seems to stay between 45-50%. My idle is down to 700 rpms again, but the engine seems to be stumbling and running rough at idle. My vac gauge is not pegged in the black at idle, its about 35% of the way over towards the red, so I think I may have a vacuum leak. Would this cause a normal speed, but rough idle?

If so I checked all visible lines, and I cannot find any leaks. I hear the familiar leak sound from the front of the engine it sounds like it is coming from behind the power steering pump. Are there hidden vacuum connections under the intake? I was able to check all connections visible at the top of engine, as well as the distributor, charcoal canister and fuel pressure regulator and they are all fine. I am having a hard time finding an accurate diagram as my car is a 1984 (only year of the motor), and is a manual trans, which looks like that means less vacuum lines than other cars with an auto trans.

I think this has probably had the leak for some time, and the previous owner adjusted the air/fuel mixture all out of whack to try and correct it.

Also noticed my oil pressure is quite low when warm at actual idle, before when it was always idling at 1100-1300 rpms it would sit just below 2. Now at 700 rpms it sits right at 1

I'll changed to oil soon and see if it jumps up at all. Thanks for all of the help so far, could not have corrected this without

1. The help of this board
2. A multimeter
3. About 10 beers

professor · #14 03-30-2009, 07:41 PM

If I were near you maybe I will share some of the 10 beer while helping you

Go to my stalling thread (do a search) on this forum and see if you missed anything. You may have to do an EHA adjustment to bring the fuel pressure to specs THEN do the air fuel mixture thingy.

geoff.doctor · #15 03-30-2009, 08:13 PM

After reading your post I think I am going to try that. Did your vacuum gauge move closer to the red at idle as well? I am quite sure the EHA has been adjusted before because you can tell the screw has been removed and reinstalled if you look at it carefully. I was hoping to avoid buying that Harbor Freight fuel injection system tester as I have spent close to $200 on tools between the 240D and 190 in the last month, but I guess it may come in handy again someday.