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Discussion Starter #1
as everyone helped me through my last ordeal. I thought ok, I have got past a couple hurdles and on to the next one.....I have the 92 sl and I have come to the conclusion that previous owner was brutal on everything but the oil changes.....believe me i'm happy he did keep up with that.....i briefly mentioned the surging idle in my " how worried should i be, oil pan discovery."

let me list the symptoms and then what happened.....

car has a surging idle. starts cold beautifully and stays at 550-650 for a little while. once the temp starts to rise so does the idle....after 80 mark on temp it could be as high as 1000-1300......I was in the middle of figuring that out or trying to......aam suggested i test some components and the codes. made the blink code reader and had some but nothing major....who knows how old they were. wrote them down and cleared them.....took for a nice long drive....after i cleared the codes the engine was up and down at the beginning or cold start....I felt like it was hunting for idle.......ran beautiful for 80 miles that day.....drove maybe 2 miles a day after that......still surging once warmed up but was happy to have her back....

had a nice day here the other day and tackled the ac strap...yes it was broke and luckily the motor was tested and undamaged. put back in as i was losing time that day...Now i can hear the motor going through the different speeds but no air out any vents. even after running some time....get back to this in a minute..

the radio hasn't worked since i got the car. I finally got the radio keys to pull the radio and ac....plug was off the back of the radio..plugged it back in and it worked... great hour or so...so happy....engine revving better than it ever has and now the radio works....i was elated...

go in somewhere for a half an hour...come back out and no radio...but i can hear this very audible click every couple seconds. sounds like it is coming from behind the dash....pull back out and fuse is good and everything is connected....

I'm thinking this has got to be electrical.......it started raining right before the radio gave out....i got out an opened the hood...noticed a tiny bit of water under the master cylinder compartment and yes there is wires down there....drains are clean and i don't know how it got in there.....driving home with no radio and the

gas pedal got extremely heavy......what i mean is i felt like i was pushing hard and only going forward with the pedal a bit......i was struggling to get to this parking lot as i was loosing speed....parked....looked under the hood...got back in and noticed it was not quite as bad and drove another block to a bar that i was headed to....went in for 30 minutes and came out with a friend and it started right up pedal was fine but not it doesn't sound like a happy engine.....get her home and pull codes.....got a single blink and everything except pin 3 and 10...3 is cfi fuel injection and 10 is top and i know that has issues...
codes were

27=data exchange between cfi control module and ignition control interrupted
28=intermittent contact in engine coolant temperature sensor circuit
29=cfi and ignition control reading diff. temps from engine coolant sensor. faulty sensor or wires....

I'm going to change the sensor. due I have wiring problems? it is a 92.

rollbar and top do not work. radio doesnt' work at the moment and i was just wondering if they could all be connected in the same wiring?

aam i'm picking up the o2 sensor tomorrow morning along with another fuel filter.....

i have found that a lot of factors can play into this but i know the car was code free before this happede....anything else that can set off these codes....

how do i attack this electrical beast....
 

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You can start with the results of those codes......

I don't remember... the engine harness replaced?

Throttle, RPM, fuel, traction, Throttle Actuator, ICM ( I hope not $$$), peddle position sensor, a module, sensors up the wazoo.......

All interconnected to make the thing go. Check sensors ....
Find another '92, with no codes /dash lights.... Then swap parts to see which one is the culprit. Have a diagnostic computer there.

Oh, yea....... cash.....

It's a tough nut to crack.

Or...... drop in a small block chevy.
 

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Discussion Starter #3
no engine harness original....pedal is ok as far as you don't have to press it in an inch before it moves....only codes are above....not one dash light on...and they all work...i'm hoping it is not electrical harness but mine is 92 and although i understand that could happen...i'm not in that 93-95 range....

change the coolant sensor and go from there....
 

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no engine harness original....pedal is ok as far as you don't have to press it in an inch before it moves....only codes are above....not one dash light on...and they all work...i'm hoping it is not electrical harness but mine is 92 and although i understand that could happen...i'm not in that 93-95 range....

change the coolant sensor and go from there....
peddle P O S I T I O N Sensor is a cute little switch mounted inside your gas peddle arm. A 10" wire runs to the right foot well wall under radio area just next to the well panel. It senses how much gas throttle you are pressing.

It's called ASR switch (If you have it on your year)
 

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Discussion Starter #5
ok..thanks i'll check that out. i did not get the o2 sensor....the 1992 ford mustang 5.0 will work correct. I know i need to wire it. lost time today and did not get down to check the spark. did do some electrical testing today. battery 12.5v
ignition on 12.2
running 14.5? is this high?
didn't have anyone to turn it over while i was testing.....

checked pin 3 on ezl x11. had a steady voltage of 6 before ignition on. with engine at idle at operating temp i had an average of 3 and when reved to 2500 i got up to 6.4 average. idle seems low to me as i followed the advice here. BOSCH KE3-JETRONIC MIXTURE ADJUSTMENT does this mean its running lean? get more info in the next couple days...thanks
 

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Just a heads up.

The engine temperature sensor talks to the CIS and the computer.....

The 02 sensor, I cut the wires, asymmetrical, so they can go in the cover.
Pulled the cover back, soldered, taped,
and then slide the cover over the wires. ;)

So no water, dirt, etc can go in.

Regards,
aam.
 

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Discussion Starter #7
waiting on parts

its been 5 days. I ordered the parts on the slow train as I have a ton to do with work. I did attempt the o2 sensor which was a bear. a damn grizzly bear.
heating it up, PO rounded the edges or whoever touched it last and not to mention i think they torqued it down.....what a pain in the az. parts will be here tuesday.....I'll let you know what the results are and go from there....thanks
 

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Discussion Starter #8
question. I'm getting the coolant engine temperature sensor codes on the diagnostics.

ordered the parts and they came in today. Is the coolant engine temperature sensor the 4 prong one or is the water engine temperature sensor right next to it with the blue top that is causing this error. I ordered the 4 prong engine sensor that talks with the cis ??????
 

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Greek God of the R129
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The 4 pin is the one you are after.
The blue top is the a/c 130C cut off.

But it is better to read the Ohm's on the sensor before you buy a new one.

Right now my mind is......on women. Haha.
There is a chart it is temperature sensitive.

Regards,
aam.
 

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Discussion Starter #10
sorry for the delays.

Ok. before christmas is the busiest time for what i do with work.

I received the parts and finally got around to putting them on. Changed 4 pin sensor/ engine coolant sensor. also 02 changed. I thought they changed the idle but after she warmed up she got nasty again.... up and down on throttle with no foot on pedal.

had an issue with the oil pressure guage on the dash. changed out oil pressure switch on oil filter housing. I think its fixed but in my opinion it stays around 3 bars a lot. I don't know if i'm just not used to it or it really is to much. Question.....while cold it will stay at 3 bars and when does the pressure drop to 2 bars at regular idle? is my surging idle keeping it at 3 bars a lot.????

thanks everyone and have a happy holidays.
 

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Discussion Starter #12
been driving a few days now.

Question? That o2 sensor was a real pain. but i did get it off. I haven't done a whole lot of work by the driveshaft so i figure a question not asked is very dangerous. This may sound simple but I don't want serious damage. While i had both front tires in the air, I had to remove the trans plate where the trans mount is. I supported the crossover member from exhaust with a bottle jack while i had it off. The drivers side had gotten jacked up another inch or so and I completely forgot about the bottle jack. When i got under her i noticed it was an 1 1/2" below where it was supporting. My question is can the drive shaft support itself or is there a chance it got lowered by my error???????

I don't feel anything when driving like major vibrations.

by the way the trans mount was shot and one is on the way. flex discs looked good. Still got the high idle issues when warm hot. The car seems like it should have more power. where are the best place to look for vacuum leaks? after changing the engine coolant temperature and driving a bit the car has no codes and no lights on.
 

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Discussion Starter #13
update

did some tests. here is what i got.

lambda between 3-2 pins on port on drivers fender.
8 v on 1st try with key on engine off. battery at 12.2 volts before key turn
7v constant on 2nd try. if i depress the air flow sensor it went to 10.42 volts.

lambda test while operating temp, no ac engine at operating temp. ranges from 3-6.8 but what was strange is that once it got in the low range it would jump all the way up to 6.8 then trickle down to 3 and shoot back up. it would go in .1-.2 intervals down to 3.0 then would jump back to 6.8 and go down slowly.
battery before during and after cranking. 12.2-9.6-14.00 which creeped up to 14.36. I was working on the car and had a little drain on battery. after tests it was a 12.7.

none of this seems right....can anyone help.
 

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Is the brake booster hissing when you step on the pedal?


Like this, driving no hiss, stopping hissing sound.
 

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Discussion Starter #15
booster

if it is subtle i haven't noticed.

if it is loud i think i would have noticed unless thats all i'm used to. I will double check it. i have radio only part of the time so i do listen closely. the last owner did do oil changes which i'm thankful for. but the rest. i'm catching it up..
 

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if it is subtle i haven't noticed.

if it is loud i think i would have noticed unless thats all i'm used to. I will double check it. i have radio only part of the time so i do listen closely. the last owner did do oil changes which i'm thankful for. but the rest. i'm catching it up..
If its not hissing.





1. Verify that there are no vacuum or false air leaks and no leaks through Air Conditioning vent system or in door lock system. Verify brake booster not leaking vacuum, test idle vacuum supply to hose at Electronic ignition control module (EZL) N1/3. Idle vacuum at 600-700 rpm (specified idle speed) should be 17"-20" approximately.

2. Check adjustment of throttle linkages and transmission kickdown cable. Verify throttle is closing all the way, test operation of throttle switch in M16 by following Mercedes-Benz Electrical Test Procedure (ETP) for CIS-E system step 23.17.0 and 23.17.1.

3. Using an impulse counter or scan tool, check for stored and current DTC's in CIS-E control module. If vehicle is equipped with a pushbutton at Data Link Connector (DLC), the blink code method can be used. Clear adaptive memory.

4. Using an ammeter, test current flow through IAC valve Y/6. At specified idle speed current flow should be approximately 700-1000mA.

Or.





1. Inspect all wiring harnesses on the engine, especially around injectors, camshaft adjusters, at rear of engine where it connects to the firewall. If the wiring is brittle and feels like sand when rubbing the harness between thumb and fingers, or if the sheath is cut back and the insulation on individual wires is crumbling and bare wires are evident, replace the wiring harness before continuing testing. Perform the same inspection on the wiring harness connected to the throttle body module. If it has faulty wiring, the throttle body module will have to be replaced.

2. If wiring harness inspection shows no defects, check all fuses in base module, fuse panel, etc.

3. Using a fully functional M-B compatible scan tool, access EA system and look at data stream information for M16/1S1 safety contact switch and M16/1S2 Closed Throttle Position (CTP) switch. Clear DTCs, start engine and read data on both switches at idle, the CTP switch should show closed, the safety contact switch should be open. Depress accelerator and watch scanner, CTP switch should go open. Usually above midpoint throttle, or before, the safety contact switch should close. If it doesn't function as described the throttle could be in limp mode, or faulty.

4. If using a M-B compatible scanner and it won't communicate with EA electronic control unit, it could be faulty throttle module or EA control unit.


Or.


OVPR:

Locate the relay on the vehicle. Sedans always have the relay underhood. W-107 roadsters have the relay mounted in the right kick panel above the fuse box. W-129 roadsters also have the relay underhood. Verify the voltage output from the Overvoltage Protection Relay, which utilizes a Zener Diode. The relay is designed to go open when system voltage spikes in excess of 20V. This can happen during a jump start or battery charge. Check the fuse in the relay. Do not rely on visual inspection. Test the fuse with an ohmmeter or just replace it. Retest for the problem. If the problem is still evident, unplug the relay and attach a jumper wire from the relay socket pin 30 to however many pin 87 outputs there are at the relay socket (depends on application). Retest for the problem. If the problem is corrected, replace the overvoltage relay.



I have said it once, and I will say it again. DO NOT JUMP START OR USE YOUR MERCEDES TO JUMP ANOTHER VEHICLE!

And only use a trickle charger to charge, a battery booster is too many amps too fast.


Believe me when I say this even if a fuse looks good, that does not mean it is. Check it with a meter.
 

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Discussion Starter #17 (Edited)
thanks

i will post results as i go....thanks for the tests. really ........appreciate your help.....:D

engine temp (4 pin ) sensor codes have not returned.. this however has shown up. taken from one of my posts after thinking no codes present.

at intake air temperature sensor in left intake inlet by grill is 4 volts at wires. sensor was around 2.6 ohms at 0-5 celcius.

Have the 16 pin dm. pin 14 keeps giving off number 9. pin 14 is the diagnostic module when looking on the chart. what i'm seeing is intake air temperature sens or signal. open or short circuit(right bank in 120) Am i right with the code?
next. when i bought the car there was a wire on the right side (passenger) with an electrical connection on the end. *****I seem to remember seeing it after the big air tube to filter housing was removed on the passenger side.****** it was about 5 feet long. its gone. i couldn't find the connection point before i knew of this site. This is the only code i'm getting besides soft top codes.
IF anyone could tell me where this runs to and from or circle a couple things on a picture of your engine it would help me a great deal..
On the drivers side air intake there is an air meter in the tube next to the drivers side headlight. This could be it but I keep thinking back to the wire and electrical missing part and think that has to be the proble.
 

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Discussion Starter #18
booster

i went out today. i do here a noise when pressing the brake down. it is a shhhhhhh shhhhhhhhh shhhhhhhh. about as loud as you would shoosh someone at a library is the best way to describe it. i'm hearing that while inside the car. running.

today i tested all the fuses in engine compartment, module compartment and trunk. with multimeter. while there i cleaned all connections and changed some fuses.

pulled off vacuum line at ezl and seen 17#'s of vacuum while idling cold/cool.

found a disconnected vacuum line for drivers side door storage compartment. i'm working on rigging some line as the po must have cut before. dont have enough line to reach...

would i do the air condition leak check in the module compartment where the 2 green and 2 red vacuum lines connect to the unit holding cabin filter?
 

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A vacuum leaking brake booster, causes a high idle.

As temp rise's so will r.p.m., without changing throttle plate position or the amount of fuel being sprayed in, until the ECM light comes on for a lean code from the o2 sensors.


Try a cold start with the booster vacuum line plugged off, so that the booster cant get vacuum. DO NOT DRIVE, while like this.

If you start it and it idles fine for 15 minutes, you nailed it.
 

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Discussion Starter #20
no You nailed it. nice work.....

:bowdown:I disconnected the line where it where it enters the booster. rigged the vacuum gauge with a carpenters nail punch to block vacuum. it ran clear up to 85 c without going above 700. matter a fact i had the multimeter at pins 2-3 at ezl and the numbers would go 6.8-5.5-5.2-,-,down to .056v. then back to the mid 6 range and slowly drop. (when it went from .056 to 6.8 the engine would stumble, be fine and when went from low to high would stumble,) i had air cleaner off while testing. towards the end it would go to 2.2v to 6.7 but still went down slowly.

1. what does this tell me? about readings at 2-3? they are supposed to go lean, rich, lean, rich? not rich, -rich -rich,lean leaner, etc.

2. the brake booster line with the check valve is swiveling at check valve. normal? or does the whole hose and valve need replaced? is there anyway i can find the brake boost leak and fix or is this a replace only part? difficulty? pointers?

mercedes mechanic: I cannot tell you how great i feel just finding part of the problem. i have spent lots of time searching, testing, etc. you made my day....thanks.
 
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