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Discussion Starter #1 (Edited)
hi all, i have a 1987 190e 16v 5 speed manual tranny. recently it started having some bad acceleration when i hit the throttle/peddle.

list of new/ recently replaced parts.

spark plug ( New oem bosch specify non resister type)
OVP relay (new)
Fuel Filter (new)
Thermal Vacuum valve (1 plastic piece broke off) new
O2 sensor (new)

This problem occur after i replaced the thermal vacuum valve with a new one. The old one had brittle plastic and broke off from contact with tools/hand.

The car starts sometime right away, sometime with a few cranks. Idles up and then settle down after 10 or so seconds. the acceleration issue is very noticeable when the engine is cold. The hesitation/misfiring happens whether its in neutral or gear. I hit the throttle and the rpm will not go any higher than 2-2.5k rpm. As the engine gets warmer the further up the problem occur. Lets say when it gets to 60c the hesitation/misfiring happens around 3.4-4k rpm. At 80c+ it happens at around 5k rpm. This is very consistent. It seems the harder the push on the peddle, the more it resist, but staying within that rpm range and dropping down slow. Even if i feather the throttle, it will still do the same when it hit those rpm range.

I also noticed that the old spark plugs were greyish at the tip. I originally thought i wasn't getting spark, but it turns out that i do.

If this is an already know issue, please help with remedy. If not, please point me to the direction on what and how to test components to make this right. Any help or insight will be much appreciated. Thank you.
 

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Discussion Starter #3
quick question, what does it mean when your air fuel reading doesn't move at all? lets say with a DMM on Duty Cycle(red on pin 3 and black on pin 2 of the x11 plug), it stays at 44.3 from cold to operating temperature. Even with the O2 sensor unplug. Now notice that i have a new o2 sensor. What causes the x11 sensor to give a constant reading like that? I know that it points to a bad o2 sensor if its plugged in, but it shows the same ready with the o2 sensor unplug.
 

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Discussion Starter #4
its seems like a bad cat is part of it. i just installed a magnaflow cat and it seems to run better. The stuttering and hesitation is still there but not very noticeable. Maybe its because the car was already warm. gotta wait until it sit for awhile. I guess the cat on the car was soo old that it doesn't get hot enough to do its job. the air exiting the exhaust seems much /warmer/hotter and the sounds deeper. there was a lot of restriction with the old cat.

I've done alot of reading, even before this thread, but my problem is a weird one. Other hesitation problem doesn't seem to have a solid solution. I need to check the fuel system for pressure. I know my fuel pump works but don't know how well.
 

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hi all, i have a 1987 190e 16v 5 speed manual tranny. recently it started having some bad acceleration when i hit the throttle/peddle.

list of new/ recently replaced parts.

spark plug ( New oem bosch specify non resister type)
OVP relay (new)
Fuel Filter (new)
Thermal Vacuum valve (1 plastic piece broke off) new
O2 sensor (new)

This problem occur after i replaced the thermal vacuum valve with a new one. The old one had brittle plastic and broke off from contact with tools/hand.

The car starts sometime right away, sometime with a few cranks. Idles up and then settle down after 10 or so seconds. the acceleration issue is very noticeable when the engine is cold. The hesitation/misfiring happens whether its in neutral or gear. I hit the throttle and the rpm will not go any higher than 2-2.5k rpm. As the engine gets warmer the further up the problem occur. Lets say when it gets to 60c the hesitation/misfiring happens around 3.4-4k rpm. At 80c+ it happens at around 5k rpm. This is very consistent. It seems the harder the push on the peddle, the more it resist, but staying within that rpm range and dropping down slow. Even if i feather the throttle, it will still do the same when it hit those rpm range.

I also noticed that the old spark plugs were greyish at the tip. I originally thought i wasn't getting spark, but it turns out that i do.

If this is an already know issue, please help with remedy. If not, please point me to the direction on what and how to test components to make this right. Any help or insight will be much appreciated. Thank you.

This is how you properly post a "my car isnt running right" Thread. what type of ovp did u use? cap and rotor and filters have they been replaced?
 

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Discussion Starter #6
This is how you properly post a "my car isnt running right" Thread. what type of ovp did u use? cap and rotor and filters have they been replaced?
sorry about that, im not very good with the forum. OVP relay is new and is a red top with 2 fuse. the old replay was also a red top. Oh yeah, all of the above have also been replaced. Everything is clean within those components.

Im still puzzle on why my duty cycle have a steady reading instead of fluctuating. Im going to have to pick up another DMM. I guess just because the DMM caused $120, doesn't mean it work well....

update: hesistation/misfiring is still happening around the same rpms/temperature as before. The only noticeable difference is that the car run alot better before it hit the rpm wall. I can't say for when its cold, but when it warms up to operating temperature, the car does not show any sign of sluggishness/hesitation at all until it hit that rpm wall(4.5k-5k rpm). I probably shouldn't be shifting that high anyways, but i never had problems before.
 

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one item to check is the fuel distributor air flow position potentiometer. bad or dirty spots on the resistance element over which the moveable wiper moves will send a bad signal to the engine computer. do a search in this forum and should come up with some threads on this topic
 

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Discussion Starter #8
Thank you for the suggestion. I went ahead and remove the intake, minus the manifold to do some cleaning checking around. 1 think i found right away, vacuum from the regeneration valve to the throttle body was unplugged. I said holy cow, i guess i'm wrong about not having a vacuum leak. Also checked the regeneration valve, upon shaking, i can hear little pellets inside. Its the material that is in the charcoal canister. Isn't there suppose to be a screen that prevent it from getting out?

I took off the throttle body housing to clean it up and found out that the vacuum passages were plugged up. I took my time cleaning it out with a very small drill bit(by hand) and compressed air. cleared it up nicely. I think the build up is from the carbon material from the charcoal canister.

the went further to the charcoal canister itself, shit....one of the hose is plugged up between a check valve(mounted on driverside wall) and charcoal canister. I guess ill probably have to replace the charcoal filter or add a screen/filter between it and the valve to prevent any carbon element from clogging up the regeneration valve. We'll see.

I haven't had time yet, but i will be checking the line that comes out of the charcoal canister back to the fuel tank, to make sure that it is not clogged up.

today, i went ahead and order and bunch of rubber vacuum connectors, vacuum lines, TB gasket, old harden hoses. Im pretty much replacement all of the vacuum lines and hose in the the engine bay. Other then that, i will be taking out the EZL crank sensor to see how it looks(maybe replacing it also).

First hard rain in a long time today, so not much is going to happen, because the car is on the driveway and the garage is a cluster F#@#. Ill probably take my free time cleaning up the rest of the air and fuel components i removed of the intake. Check the potentiometer, injectors and stuff.
 

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to properly test the duty cycle, engine must be running at operating temp 80C, all accessories off. usually if x11 output is steady it means the 02 sensor is either bad or disconnected somewhere.

on some NAM versions you need to switch the CFI control module to on/off output. tho i am not familiar with this type (mine is euro) you might want to check if you have this version which is why your x11 does not fluctuate. if you think that your exhaust is too hot it might point to a lean condition.

regards,
 

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Discussion Starter #10
Thanks raymondgallant for the tip.

Update: The dealership don't carry and cannot get the Activated Charcoal Canister. The main warehouse told them that it is discontinue part. Either replace with a used one or replace it. The funny thing is, the charcoal canister plays a major roll on emission, so it doesn't make any sense at all. From what i know, the Charcoal Canister is the same for the 2.3 16v and the regular 2.3. I fix mine by putting a fuel filter screen in between the canister and the check valve. Ill be using a clear one so i can see if it gets clogged up or not.

pulled out the EZL crank sensor and it was cracked at the tip. A nice $140 replacement from my supplier. Got in some new vacuum hose and rubber tubing and ready to install later today.
 

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Discussion Starter #11
just finished reinstalling everything. The car starts right up an idle perfectly. Throttle repose is 100% better. After a every rev, the rpm drops right back to idle without any sign of stalling or rpm hanging at 3k like before.

I still do have the popping/hesitation issue at higher rpm. Im thinking the fuel pump can't handle high volume. We'll see. I am planning on cleaning out the fuel system.

Does anyone know how to connect a fuel pressure gauge to our system so i can monitor the pressure while the car is on? I want to see whats happening when the rpm is at the higher end. If can get some help on where a fuel pressure gauge would go, if i was to to this. Thanks.
 

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I had a similar situation with my 85 16v. Floor it out of gear, and it would rev to 5k and stop. In gear, give it part throttle, it would pull to 4k before going flat, give it full throttle and it would just go flat at about any RPM. This didn't happen suddenly, I found this 16v non running and when I got it going, that's when I noticed the problem.

My problem turned out to be a CIS fuel distributor clogged up with old fuel residue, not allowing enough fuel through. It had been sitting for a few years with old fuel in it. Fixed that by giving the distributor a few hours in an ultrasonic cleaner using parts solvent as the medium, was cheaper than having the distributor overhauled ($500+).

That's probably not your issue as the car was running good previously, but it does sound like your engine is being starved of fuel at higher flow rates. Possibly a mechanical issue - pressure regulator, fuel filter clogged, tank screen clogged, certainly a vacuum leak would cause the mass airflow sensor not to deflect enough, cutting fuel flow.
 

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just finished reinstalling everything. The car starts right up an idle perfectly. Throttle repose is 100% better. After a every rev, the rpm drops right back to idle without any sign of stalling or rpm hanging at 3k like before.

I still do have the popping/hesitation issue at higher rpm. Im thinking the fuel pump can't handle high volume. We'll see. I am planning on cleaning out the fuel system.

Does anyone know how to connect a fuel pressure gauge to our system so i can monitor the pressure while the car is on? I want to see whats happening when the rpm is at the higher end. If can get some help on where a fuel pressure gauge would go, if i was to to this. Thanks.
You connect the fuel gauge as shown
 

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Discussion Starter #14
[TrapperJohn] Thanks for the suggestion. I'll look up on the process of getting a an ultrasonic cleaning. I wouldn't rule out a vacuum leak either, even though i already replaced all of them in the engine bay. The only ones i need to check is the one going through the firewall and splitting to the gauge and heater system.

[DP] Thanks for the reply with the fuel pressure gauge setup. Would it be a problem leaving the gauge connect permanently or long term?
 

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drew what type of gauge is that? im looking at investing in one but im looking at getting one thats compatable with the 190 and for later cars with the schraider valves..
 

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Discussion Starter #18 (Edited)
I just did some poking around with the multimeter and discovered something weird.

First off, pin 3 and 2 show a constant number when i check for the volt (8.4v) and/or a constant 46% AFR on duty cycle. This problem was always there, and i could never source the issue for that.

New discovery. I went ahead and try to test my NEW O2 sensor. I have a narrowband gauge connected to it to make sure that my O2 sensor is working/bounching around. Not too long after i installed my new O2 sensor, it stop working. It would just sit at a stoich point leaning toward lean. When i put the meter to the O2 sensor(signal disconnected and heater connected), I get 0 volt. It was strange, due to the fact that my afr gauge have a ready(its constant, but its a reading). I then put the volt meter to the receiving end of the signal connecter(wiring going to the CIS-E unit). What do you know, it shows 0.4 volt. WTF, why would the receiving end of the CIS-E unit from the O2 sensor put out a .4 volt?



What do you guys think? grounding out? bad CIS-E unit?
 

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drew what type of gauge is that? im looking at investing in one but im looking at getting one thats compatable with the 190 and for later cars with the schraider valves..
I got my set from Harbor Freight. It actually mentioned on the box that it's designed to check Bosh CIS.
 

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I just did some poking around with the multimeter and discovered something weird.

First off, pin 3 and 2 show a constant number when i check for the volt (8.4v) and/or a constant 46% AFR on duty cycle. This problem was always there, and i could never source the issue for that.

New discovery. I went ahead and try to test my NEW O2 sensor. I have a narrowband gauge connected to it to make sure that my O2 sensor is working/bounching around. Not too long after i installed my new O2 sensor, it stop working. It would just sit at a stoich point leaning toward lean. When i put the meter to the O2 sensor(signal disconnected and heater connected), I get 0 volt. It was strange, due to the fact that my afr gauge have a ready(its constant, but its a reading). I then put the volt meter to the receiving end of the signal connecter(wiring going to the CIS-E unit). What do you know, it shows 0.4 volt. WTF, why would the receiving end of the CIS-E unit from the O2 sensor put out a .4 volt?



What do you guys think? grounding out? bad CIS-E unit?
When you got .4V was the O2 disconnected?
 
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