Still unresolved misfires on my 300TE - PeachParts Mercedes-Benz Forum

ps2cho · #1 01-25-2009, 11:52 AM

Want to start a new thread as I am still struggling to resolve these misfires.

Here is the parts I have replaced so far:

New OVP
New Coolant Temperature Sensor
New Voltage Regulator
New Alternator
Injector's+Seals (previous owner + smoke tested)
New Fuses
Non-Resistor OEM Bosch H9DCO's
New Bosch Ignition Wires (checked for arching as well)
New Distributor Rotor + Cap + Housing
New Fuel Filter
New Breather Hoses
Used Fuel Distributor
New Ignition Coil
Used Fuel Pressure Regulator
New O2 sensor
Used EHA Valve
New Motor Mounts
-- Head work done yesterday:
New Head gasket, intake and exhaust gasket, front timing cover gasket.
Head skimmed and pressure tested
New Water pump.
New Valve Guides + Seals
-- Smoke tested for leaks
-- Compression is 185psi across the cylinders
Swapped Jetronic Brain /w used one
Swapped Fuel Pump Relay /w used one
Swapped Cold Start Valve /w used one
Swapped EZL /w used one

As you can see there has been alot of stuff thrown at this car...

It Misfires all the time and can only be felt at idle. I have done the engine mounts. After all the work I have done, it is 10x better and its a small misfire....but its still there as I can feel it.
I can also hear the engine surging rhythmically.

At this point....where should I go? Should I look into fuel delivery/computer or what?
Injectors as I have only had one replaced in my lifetime with the car?

At least I can safely say the head is absolutely 100% Perfect. Top end is set for at least another 100k miles.

duxthe1 · #2 01-25-2009, 12:47 PM

Refresh our memory, when are y ou having misfires? Idle, partial load or full load?

RAYMOND485 · #3 01-25-2009, 01:23 PM

2001 e320 55k
replace the crank position sensor i had white smoke with engine cold and replace plugs, now no more white smoke $54.00 go to this site, it will be in front or rear of top engine the buy parts section have pictures MAYBE 1 HR DIY

mrdubai · #4 01-25-2009, 01:38 PM

please explain in detail when it miss-fires... which rpm, load, if you rev it in N ?

Cheers
Horst

ps2cho · #5 01-25-2009, 03:19 PM

Misfires all the time and can only be felt at idle. I have done the engine mounts. After all the work I have done, it is 10x better and its small....but its still there.
I can also hear the engine surging rhythmically.
No difference in cold startup/warm startup/outside temperature/AC...always misfires. D/R/N still misfires. It is consistent.

I have no smoke coming out the exhaust. Performance is lacking too along with fuel consumption.

I heard that the CPS is a hit or miss. I tested the resistance and it was 800omhs IIRC which is within spec. I mean I can just replace it for good measure....but its $150...

pawoSD · #6 01-25-2009, 04:27 PM

I replaced the CPS on our 300E (which still tested within spec) and all of our issues went away. MPG's went from 11 to 22 and no more idle issues or misfiring/plug fouling. Its been 550 miles with 0 issues, not so much as a single misfire....with RESISTOR (dun dun dun) Champion plugs in it.

It starts up MUCH faster too, crank....Vroom! Right away. Its awesome!

ps2cho · #7 01-25-2009, 07:35 PM

Quote:

Originally Posted by pawoSD

I replaced the CPS on our 300E (which still tested within spec) and all of our issues went away. MPG's went from 11 to 22 and no more idle issues or misfiring/plug fouling. Its been 550 miles with 0 issues, not so much as a single misfire....with RESISTOR (dun dun dun) Champion plugs in it.

It starts up MUCH faster too, crank....Vroom! Right away. Its awesome!

In that case maybe I should too. I get similar MPG (13 average)...or at least last time I filled up. We will see any difference is made since the valve job among other stuff that was done in the past week.

Where is the CPS located? When I had the head off I was meaning to find where it was, but never got around to it. Is it difficult to reach with everything back together now?

EDIT: That reminds me...we talking Cam Position sensor here, right? The Crank position is at the front and only references for the odometer as far as I understand.

duxthe1 · #8 01-25-2009, 09:43 PM

The 103 doesn't have a cam position sensor, just a crank position sensor. As counter intuitive as it may seem, the sensor on the front of the engine isn't it. That is just a diagnostic reference sensor. The actual crankshaft position sensor is located in the rear of the engine near to the bell housing under the oil filter area. It's harness is tangled under the intake manifold and eventually snakes its way to the ignition module. Not a lot of fun but do-able to replace, though its failure is rare. I think I've replaced one in the last five years.

ps2cho · #9 01-26-2009, 12:59 PM

Okay thanks. I'll report back when I get it replaced.
Picked up another EHA valve at the junkyard yesterday because I tweaked mine and I have lost the initial setting that it was on. Got it for $5.

hihosilver · #10 01-26-2009, 04:16 PM

are you sure 103 motors have a crank sensor, I can't find a listing for my 86 300e, as I have done about the to mine valve job etc. getting ready to replace injectors and thought mine might need sensor also

pawoSD · #11 01-26-2009, 04:47 PM

The M103 has a "tach pickup" and a "Crank Position Sensor", the tach pickup is at the front over the pulley.....the CPS is at the back of the engine right under the oil filter assembly.

johnjzjz · #12 01-26-2009, 08:46 PM

i went back and read all of what you said you did i dont know who was pointing you in the changes you did --- BUT a clogged injector can be the cause - if you have a hand held heat gun ( checker ) you can see what the exhaust manifold temps are between the cylinders a cold one or an extra hot one, will be a clogged injector ( or stuck one ) BUT i will say i had a miss in a 124 a few months ago and the distributor cap was cracked dont keep changing parts till you point out what is causing the issue

if you find an injector issue you can switch the injectors between cylinders and move the miss to another cylinder than knowing it is bad than you know for sure

old school method i was taught in the 1960s as a kid was to get a sheet of text book paper cut it into a 1/3 strip and place it accross a tail pipe of a car that runs correctly notice what happens to the paper ---- than place it accross the tail pipe of the car missing if you hold it against the side of the pipe and the motor is missing the paper will make a poping sound ( cant miss the sound it will be loud ) - than by that method you can start looking

with rubber gloves you can remove one spark wire at a time and look at the engine in the way it behaves the cylinder that is the cause will have the least affect on the motors idle or it almost has no affect when the wire is remover

CAUTION the live plug wire will bite you if your careless about holding it, think of it as a rattel snake, RUBBER gloves and rubber handle plires and pre remove the plug wires so they are just at the ends of the plugs and pop right off with no effort it will make it a lot easer to do it that way -- i still think its an injector after reading your post of course it is about the only thing left -- jz

tinypanzer · #13 01-26-2009, 10:04 PM

Man, you've done just about everything to that car! Don't worry, once you figure this misfire out you will be happy with it for a long time.

My gut tells me that indeed an injector might be the problem. I don't think it would explain your horrid gas mileage unless it was leaking fuel all the time. If that's the case, you should have a plug that looks quite different from the other 5. Since you just re-did your head, I would go ahead and pull the plugs now and see what they have done since you put your head back on.

CIS injectors are funky things. They don't have a solenoid, they open and close purely by the pressure put on them. If they go leaky, a lot of things can happen. First the nozzles get cloggy with varnish and spray pattern suffers, and if they really stick open bad you get fuel pouring into the manifold. If this is happening, the evidence would be in the manifold with excessive varnish deposits. Also, if this is happening, logic would indicate that a hot-restart would be very difficult as you would lose your fuel system pressure rather quickly and you'd have a ton of fuel in the cylinder that was bad. I've even heard of hydraulic locking occurring on CIS systems with bad injectors.

An injector that is not opening properly sounds more likely when looking at your motor's guts, but that doesn't explain the mileage problem.

I went back and looked at the photos you posted when you had the head off, and I don't see any obvious signs of flooding injectors.

Maybe what you've got here is several injectors that are fouled from bad gas or from an extended period of the car sitting. If you had several injectors with poor spray pattern it could explain everything.

Have you tried running any sea foam or similar through the fuel system?

Good luck!

-tp

tinypanzer · #14 01-26-2009, 10:42 PM

Y'know, going back and looking at your intake manifold pics from your previous thread, take a look at how dark and varnished the intake manifold is in cylinder number 4 versus say, Cylinder number 2. Maybe it's just the picture or lighting, but it looks to me like there is waaaay more varnish in that cylinder.

Can anyone say if that amount of varnish is normal for this motor?

-tp

ps2cho · #15 01-26-2009, 10:47 PM

I replaced a number of items just from reading....This is my first car (I'm 20) and I didn't know a whole lot so I just replaced alot of stuff for a general tune up along with others that could be potential culprits.

I have pulled each spark plug individually and they all equally cause the car to miss harder. Resistance on all spark plugs are perfect (I double checked it even though I bought a new set).
I believe my dads DMM has a IR temperature sensor on it...will that work good enough to test the injectors via the manifold as you suggested?

Also...Is there a way to reset the EHA to its original setting? I kinda fiddled with it a while back and I lost the position where it was originally set at. I checked the MB CD's, but it only mentions replacing it...nothing about testing it. I understand it is a very critical part to maintain a stoichiometric ratio (this is not my misfire cause though because I both richened and leaned it out a long time ago to see if that was the problem). If the EHA was a problem then it feel as if the car is starving for fuel...not a misfire, correct?

Oh and yes I've ran Seafoam through her.

Thanks guys!

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