I am now at a dead end.

While driving to breakfast this morning, the engine began "missing"; running very rough. After getting home, I pulled the plugs with hope of identifying the problem cylinder. All six plugs looked the same. I checked the resistance on the plug wires and "plug stub" and they were 1.5 to 2K ohms (within spec).

I then checked the fuse on the over voltage protection relay and it was good.

I also checked for malfunction codes; pin #8 (HFM-SFI) responded with one blink (no malfunction). The check engine light is not lit.

The wiring harness has been replace on this car.

The only other clue is that the exhaust smells rich.

Could this be an over voltage protection relay?

Anyone have other tests or ideas?

__________________
Jim Villers
190SL, 230SL 5-speed, 95 E320 Wagon, 01 E320 Wagon, MGB, Boxster 'S', 190SL "Barn Find"

Hey Jim,

Long time since.

Pull the OVP and see if it is 000-540-52-45..
If it is , change it to the new part # 000-540-67-45

__________________
A Dalton

Arthur .... Yes, it has been a while. With your 5K responses, I can see where you have spent your time after your 2K responses on the pagoda board. I am slow, I only have 3K with the 190SL Group.

Anyway, the OVP was also my guess as that would explain the lack of a malfunction code (still with the reader you send me in 2001). So I have a new 00 540 67 45 in my hand that I'll install tomorrow. If that dosen't work (or change anything) I am not sure where to look. I'll post the results tomorrow morning.

Thanks again, you always seem to be around when I need assistance.

__________________
Jim Villers
190SL, 230SL 5-speed, 95 E320 Wagon, 01 E320 Wagon, MGB, Boxster 'S', 190SL "Barn Find"

Very good..I think the OVP will do it..if not , we will go to the next step, but those HFM/SFI OVP set-ups are infamous and where we always start b/c that chassis is full Electronic and OVP is mandatory..if you pull it, the car will not run , whereas on the earlier models the car would still run b/c OVP was just on the control side. It is nice to see you have a single flash on pin 8..that is a real good sign on that chassis ..most have somethin in there..I think that new harness took care of that.
Have not been at Pagoda much..but I do go over once in a while to read some of those long -winded post...........and I mean Looooong..
Nice talkin' to you again.

__________________
A Dalton

Arthur ..... I need "plan two". I installed the OVP this morning and it is still "missing" or running very rough.

You might want to visit the 190SL site and see my current "Barn Find" project project. It had last run in 1988.

My next thought would be in the fuel pressure area (probably not trip a malfunction code). Could it be the fuel pump or pressure regulator?

__________________
Jim Villers
190SL, 230SL 5-speed, 95 E320 Wagon, 01 E320 Wagon, MGB, Boxster 'S', 190SL "Barn Find"

< >>

I would check it... These HFM will fool you b/c if the HFM module sees an ignition misfire , it automatically cuts fuel to that cyl. injector for CAT protection, so an ignition failure on these seems like a fuel issue.
But fuel pressure is a next step.
On the top of the fuel rail, you will see a test port cap..That is where you can hook up a gauge. That fitting is the same as an R12 fitting, in case you do not have one.
So, first check is to start the engine and let it idle..now, pull the vac line at the regulator and see if any gas is shooting out that port on the reg. There should be none and if there is, the diaphragm is leaking and you need a new regulator. [ raw, unmetered gas getting sucked intio intake.]. Also check for any evidense of fuel in that vac line..again, you want none.
If all is well, then hook up gauge and do this simple 3 part test.
1-Engine @ idle, Vac line ON-- FP should be 3.2-3.6 Bar
2- " " , Vac line OFF-FP should jump to 3.7-4.2 Bar
3-Engine OFF , wait 30 min. -FP should maintain at least 2.5 Bar
*Bar = 14.5 PSI... [ you already know that, but this winds up in archieves]

See what's up w/FP...
..next suspect would be the 3 Resistor under the coils if we have a missing/misfire condition, or a vac leak could fit a Rough running condition.
If intermittant, that could be a sticking EGR [ common on 104] . I have a simple test for that after we see where you are w/FP.
You may aso want to try the DM led/sw [ the built-in one] while at idle in case there are any impending codes...
Are you using Bosch F8DC4 plugs?

__________________
A Dalton

i HAVE BEEN THRU THIS AND WILL BET YOU IT IS THE OXYGEN SENSOR EVEN THOUGH THE LIGHT IS NOT LIT....GET ONE OFF EBAY FOR CHEAP AND IT WILL MAKE YOUR CAR RUN LIKE NEW.

Arthur ..... Great use of my old R12 gauges (I sold my last R12 car).

It does not appear to be a fuel pressure problem; Idle with vacuum, 55 psi; without vacuum, 61 psi; with engine off, 50 psi. Possibly a little high but very close.

Checking the plug "thing" under the coils was one of my first checks. I tested them with an ohm meter and they, and the wires had 1.8-2K ohms. I believe that I replaced them long ago at your recommendation.

I am not sure of the plug numbers but they are Bosch copper from my local dealership (they give me good prices so I buy a lot from them. With my discount, even 190SL parts are cheaper than the speciality suppliers).

I guess that ERG is next.

I checked the LED (in the DM) readout with the engine idling and received a 7 code, "Ignition System failure". This sounds promising but I am not sure what it really is saying. After a search and some reading, I'll pick up three of the connectors under the coils and a new set of F8DC4 plugs.

Is there a way to test the coils? There is no resistance between the center tap and ground.

The oxygen sensor is another "easy" replacement part. I'll pick one up next time that I am out.

__________________
Jim Villers
190SL, 230SL 5-speed, 95 E320 Wagon, 01 E320 Wagon, MGB, Boxster 'S', 190SL "Barn Find"

<>

Yes, that is why I mentioned it..I just use the R12 ends on a good fuel gauge..very nice.. if using your old gauges , you can also use the manifold valves for fuel flow rate test...cool.

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Fine...........

>

Ok ..here is what to look for on those connectors..[ just the ones under the coils].. They don't "snap connect" to the plugs like the other 3 wire lead plugs that stand alone ..and b/c they are under the coil, benz used a simple spring arrangement that just pushes down on the top of the plug connectors from the force of the seated coil..not a good connection set-up, but I see why they did it with the coils being on top of the plugs...anyway, if you look in there and see any heat fatique or grayish ash type residue, or spring degeneration on that spring and connection, that is where the failure and misfire has/is occurred.. look for any carbon type tracking right there and around the plug base....an ohm reading of the connector does not address this condition. Each coil fires 2 spark plugs at the same time [ Waste Spark System] in Series, so a poor connection at this point will cause a misfire very easily ..which is why most Techs [ knowing this failure rate] just change those 3 connectors when changing plugs. As I posted earler, once the HFM [ ignition] module sees this misfire , it cut off injection, so the misfire is pronounced and often erratic. A scope does pick these up , but if one does not have that, a close look at those connections may show the condition.. I am pretty sure I advised you when you did the harness to go with the Bosch Super Coppers , so it is most likely that you do have/ did go w/F8DC4's ..and I only stress that point b/c 104 are very fussy about plugs being a Waste system.. and they HATE plats!!!!
I also use a little die'electric grease on these connectors.
On the EGR, there was a Benz TSB for sticking valve and it was remedied by replacement to one with a smaller shaft dimension. I have that Campaign Info, if you need it , but a simple EGR hand test should suffice.
With car up to temp and @ idle, take a hand vac capable of pulling 12-14" vac and apply that to the vac port of the EGR and hand vac open the EGR..the engine should immediately try to stall/run rough . Now the trick..With hand pump, quickly release vac supply and listen for the EGR to SNAP shut. The engine should return to perfect idle if all is well an egr is completely closing..do this several time and actually try to get it to hang up..if NO, then I would not suspect EGR leakage. But that test would not eliminate other possible vac leaks. It is just possible EGR confirm.
[ if no change in rpm with this test, you have another problem, but will wait for results on this one]

Finally , I doubt you have an 02 sensor problem , but they are fairly easy to test on that model b/c it is full electronic engine management.
Under the passenger rug is the 02 wires. The green one gets unplugged so that no sig goes back to ECU . Now , the blk wire that plugged into the green is 02 sensor output. You can connect a DMM + there and a good ground.
Now , with engine @ temp and a decent idle, watch your meter as you remove the vac line to the FP regulator [ cap the line with your thumb so you don't create a vac leak while doing this test].
This will make the reg increase the FP and that increased pressure will cause a manually induced RICH condition to the engine and will show right up on the 02 as a high voltage [ .8-9v].. That is the rich test for 02. The engine can not correct for this b/c it does not have an 02 input sig. going back to the ECU b/c you disconnected the green wire..
Now , hook the vac line back up to reg and then take a good sized vac line OFF somewhere and watch your meter go LEAN..[ .1-.2 v].. That test 02 ability to read LEAN condition....now , to test the switching speed , I take that line you are using for the lean test and put my thumb over it , on and off, while watch the DMM..it shoud react to your on/off input of air through that vac line pretty fast. If so, you have a decent 02.
A scope pattern is much better, but this is a viable DIYer test on HFM systems..what you are basically doing is using the engine as a Lean/Rich generator and simply seeing if the 02 has the ability to react to you manually causing a rich or lean condition.
I would start with a closer inspection of the connectors under the coils and then the egr test..both simple...and check the plugs while you are there.
...and see if any pending codes on DM

__________________
A Dalton

<< >>

Jim,

I did not see this added info when I wrote you my last posting b.c you added it while I was answering the original posts..

.... but , with that new info, that would certainly help confirm my suspect of the coil connectors under each coil...
If the N59 DM sees a malfuntion from the HFM ignition system, it brings on a pending code before CE lamp activation ..if it does not see subsequent repeat failures , it will drop it as a viable fault before it activates the CE. [ intermittant problem]
If you have coil problems , they are output/current monitored by HFM Ignition Module via pin 8 and would show as a code 21/22/23, depending on which one was in question..
So , with this added info from the DM, we are back to coil connectors as first possible suspect...and plugs while you are in there... this will most likely turn out to actually just being your basic/common HFM/104 ignition connector failure complaint/remedy.
Have fun..............

Arthur ..... From you description, it is easier to change the oxygen sensor than to throughly test it. I would just put a digital volt meter on it and watch the voltage; if it cycled up and down, it is OK.

When I inspected the coil bottoms, there was some gray power that I just ignored. I'll replace them before doing anything else. It will be Monday before I can get the parts.

Thanks again.

__________________
Jim Villers
190SL, 230SL 5-speed, 95 E320 Wagon, 01 E320 Wagon, MGB, Boxster 'S', 190SL "Barn Find"

< >>

I agree.. The posted procedure is actually harder to read than to do..I just posted the full procedure if anybody with HFM really wants to know how to get a close check w/o a DSO wave pattern from a scope... by simply removing or adding a couple of vac hoses at the engine while watching the 02 sig.
I use/have some nice equipment , but I try to give the DIYer the same diagnostic abilities using what he would mostly have in his Tool box..which is usually just a DMM , with maybe freq and duty cycle at the most...
So, I have to tone it down, but at the same time try and get the general idea across..
With the 02 sensor wires right there under the rug, it is a simple matter to hook up and monitor while driving..some guys hook a permanent meter right on the dash. Some also use that connection to hook those a/f mixture Led readout gauges you see around.
One thing that should be mentioned on 02 sensor replacement on this or later Benz chassis [ both OBD1/2] is the fact that using a generic sensor
will cycle fairly well for fuel mix control, but the other systems [ Like AIR] require the correct relacement OEM b/c they are capable of reading the ultra lean conditions the ECU looks for on Emmissions mandates and if one does not use a sensor with this quality and precision, he runs the risk of codes when the ECU does its self testing procedures.

We will see what happens when you change out the connectors...
See ya

I have been following this post--I have a 95 E320 with similar symptoms.

While reading, it once again occurred to me that the readers of this forum are very lucky to have someone like Mr. Dalton as a regular contributor.

Thanks again from a very appreciative forum member.

J. M. van Swaay

Danke J. M. van Swaay...................

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A Dalton

I always admire your very scholarly input re member problems and have often wondered about your background related to these cars. Would you mind sharing a little bit of that with us?