1988 300TE Misfires -- Let's get this fixed! - Page 2 - PeachParts Mercedes-Benz Forum

ps2cho · #16 01-26-2008, 09:30 PM

Is the location of the O2 sensor the same on the W124's and 126's?
This is a pic from a w126

Is it the same place?

ps2cho · #17 01-29-2008, 08:46 PM

Well I just got done.

Still misfiring.

Sigh...This will never be fixed.

Updated original post to include O2 sensor now.

ps2cho · #18 01-30-2008, 07:43 PM

Just replaced the EHA valve with one that came with my fuel distributor. Car is more responsive, but misfire was unaffected.

ps2cho · #19 02-02-2008, 10:51 PM

bump

Ivanerrol · #20 02-03-2008, 08:04 AM

If you remove the electrical wires for the EHA and IACV then the car will run on without sensors. This puts the car into 'K' Mode and not 'KE' mode. The O2 sensor throttle position switch and temp sensors will not have an effect.
If the car still misfires in this condition then it wont be the ECU commands that are causing it.
If there is no electronic control of the injection and you are still getting the misfires it will be elsewhere.
Have you had the fuel pressure check done? If so what was the result.
Did your Indy Bob put another set of leads on to check? Even new ones are known to have some quality issues.

ps2cho · #21 02-03-2008, 10:25 AM

Quote:

Originally Posted by Ivanerrol

If you remove the electrical wires for the EHA and IACV then the car will run on without sensors. This puts the car into 'K' Mode and not 'KE' mode. The O2 sensor throttle position switch and temp sensors will not have an effect.
If the car still misfires in this condition then it wont be the ECU commands that are causing it.
If there is no electronic control of the injection and you are still getting the misfires it will be elsewhere.
Have you had the fuel pressure check done? If so what was the result.
Did your Indy Bob put another set of leads on to check? Even new ones are known to have some quality issues.

I've pulled the plug to the EHA before, but not the ICV. I'll give that a try.

No he didnt have any other leads, I still need to check resistance in the wires to double check they are good.

ps2cho · #22 02-13-2008, 01:57 AM

Bump. The temperature in so-cal has heated up in the last few days and the car has been significantly worse...

I have two things:

1) I have an error code for my Coolant Temperature Sensor (Water-temp sensor?)...could this have any relation to the misfires worsening with the outside temperature higher?

2) What about Crankshaft Position Sensor? Culprit? Any way to check these?

designo? · #23 02-13-2008, 07:45 PM

I believe the coolant temperature sensor would affect the ignition mapping.
A thermotime switch would affect the cold start enrichment.

The above can be checked with an ohm meter.

The CPS can be checked most effectively with a scope.

ps2cho · #24 02-14-2008, 09:56 AM

Quote:

Originally Posted by designo?

I believe the coolant temperature sensor would affect the ignition mapping.
A thermotime switch would affect the cold start enrichment.

The above can be checked with an ohm meter.

The CPS can be checked most effectively with a scope.

Ok thanks. Well the cold start is fine and dandy, so just the sensor is in question.

designo? · #25 02-14-2008, 10:40 AM

See the follwoing thread:

http://www.peachparts.com/shopforum/showthread.php?t=165715

Near the end of the thread, I posted some info on the CPS. Generally, the CPS outputs a waveform and the computer interprets the signal.

Zeus · #26 02-14-2008, 10:58 AM

ps2cho - I'm not sure if this has been mentioned, but have you replaced the motor mounts? With my 300E, the engine was rough at idle with the vehicle in park. Felt like a misfire, but it turned out to be the mounts. I had them replaced and the car ran so smoothly I couldn't feel the engine at all, it was incredible the difference it made.

Beautiful engine pics! My 300E was that clean as well, what a great engine. My poor M113 is nowhere near that clean (and uses oil).

Good luck!

brewtoo · #27 02-14-2008, 12:15 PM

Maybe your engine is too clean! It really is beautiful.

Good point about the motor mounts. The engine will sink and you will have all the vibration transmitted to the chassis.

bpaz_ph · #28 02-14-2008, 01:16 PM

I saw your previous thread about the "spark plug horror". Is it possible that there's too much carbon build up in your combustion chambers causing pre-ignition.

Just a thought.

ps2cho · #29 02-14-2008, 01:22 PM

Quote:

Originally Posted by bpaz_ph

I saw your previous thread about the "spark plug horror". Is it possible that there's too much carbon build up in your combustion chambers causing pre-ignition.

Just a thought.

Once we did the valve steam seals, that fixed the oil consumption and buildup on the plugs, so wouldn't some hard driving and fuel/injector cleaners rid of anything, or at least make some difference?

Quote:

Originally Posted by Zeus

ps2cho - I'm not sure if this has been mentioned, but have you replaced the motor mounts? With my 300E, the engine was rough at idle with the vehicle in park. Felt like a misfire, but it turned out to be the mounts. I had them replaced and the car ran so smoothly I couldn't feel the engine at all, it was incredible the difference it made.

Beautiful engine pics! My 300E was that clean as well, what a great engine. My poor M113 is nowhere near that clean (and uses oil).

Good luck!

Thank you!

The car has been really taken care of along with the low mileage.

I would absolutely get the mounts done, but the misfire is inconsistent that's what leads me to believe its not the mounts. If it were the mounts, then theoretically it should feel basically the same every day. Problem is that it does not. Some days it can hardly be felt (hardly ever, but does happen) and other days its like a portable earthquake when idling.

Zeus · #30 02-14-2008, 01:47 PM

Quote:

Originally Posted by ps2cho

I would absolutely get the mounts done, but the misfire is inconsistent that's what leads me to believe its not the mounts. If it were the mounts, then theoretically it should feel basically the same every day. Problem is that it does not. Some days it can hardly be felt (hardly ever, but does happen) and other days its like a portable earthquake when idling.

Hmm...did you physically check the mounts? How about shifting into reverse when parked, does it get rougher? Can you inspect them? I've found that the amount and frequency of vibration from failed mounts can really vary...so it is hard to pinpoint until you diagnose them.

My E430 has had a rough idle, which was getting a bit worse. I had codes for the front O2 sensors (sensors 'aging' code) so I replaced them and that helped quite a bit. Still a bit of a roughness though and I am suspecting the mounts as they are likely original (and 144,000 Km on the car). So I will probably be changing them soon...mileage and performance are fine otherwise.