Duty Cycle Readings 91 M103 300E - Page 2 - PeachParts Mercedes-Benz Forum

400Eric · #16 03-13-2010, 04:57 AM

I thought you where gonna nab some ECUs from the U-Pull-It?

JohnM. · #17 03-13-2010, 05:54 PM

Well, waiting on a guy I know local who probably has one I can swap in quickly to test. The two big yards here in Denver have online inventory and there is nothing newer than 1989 for W124. The other large one has no inventory, but it's a long drive. I'm hoping that by monday I can rule out the ECU....

400Eric · #18 03-15-2010, 04:03 AM

I had to go back to the U.P.I. today so I went ahead and nabbed the only 90 onward 3.0 M103 W124 ECU that was there while I was there. MB part number 011 545 01 32. It was in a row that is overdue to be crushed. I figured it was better than it going to the crusher. Let me know if you don't find one in your area. I'll only ask the yard's price plus shipping. The only thing we need is for a fellow board member in this area to let me run this ECU in their car for a few minutes to make sure it's good since my M103s are too old to be compatible. I also have a multimeter if you'll tell me what tests to run and how to do it. I'm afraid I'm not as knowledgeable about CIS-Es as I am about LHs. (Not that I'm any kind of expert on LHs.)
Regards, Eric

Cal Learner · #19 03-15-2010, 06:31 AM

Hey Eric, that's a nice gesture, man.

loepke72 · #20 03-15-2010, 12:28 PM

As long as the duty cycle is changing roughly 2 times a second, the system is able to adjust the mixture around the ideal. Does not matter much if it's at 2V or 10V, although ideally it will be around half of battery voltage so there will be enough range on either side to correct the mixture under other operating conditions. Just make sure the reading is still switching both at idle and at about 2500RPM. If so, go get the car retested for emissions.

Also, yes, the A/F adjustment is VERY sensitive; it does not take but a small fraction of a turn to make a big difference in the duty cycle reading. Also, wait for it to settle before readjusting.

400Eric · #21 03-17-2010, 01:54 AM

Please folks we need a 90 to 92 3.0 M103 W124 in So Cal to test this ECU on. Can anybody help?

JohnM. · #22 03-21-2010, 03:58 PM

Sorry guys. Been busier than busy. 400Eric, sorry for not responding about the ECU. I got a call from my local friend right after I sent you that PM.

Anyways, the new ECU defintely improved things, but something is still amiss. The system is actually going into closed loop now, and the voltage is switching very quickly like it should. I was able to adjust my idle CO mixture, but when you bring the rpms to 2500RPMs it slowly pegs to full rich! 6.5-7.5 volts at idle, bring and hold at 2500rpm and it incrementally pegs to 10.5-11.5V!

Fuel pressure regulator? What else could it be???

I don't have much more patience for this.

JohnM. · #23 03-21-2010, 05:39 PM

!!!!!!VICTORY!!!!!

ECU was the reason I failed emissions just recently, and the EHA was the reason I almost failed two years ago!

My theory: My car had a reman'd Bosch FD installed sometime before I got the car. I believe that the EHA had been previously adjusted to compensate for the old FD and they didn't re-adjust it when they installed the new FD!

I very slowly adjusted the EHA CCW 3 separate times and noted the change at 2500rpm. Ended up being a total of 1/4 turn all-in-all. That brought the duty cycle readings down fully within spec at RPMs. Now it's perfectly adjusted at idle 6.5-7.5 and the same range at RPMs. Yay! Stupid PO (or Stupid PO's Stupid Mechanic)!!!!!

ps2cho · #24 03-21-2010, 09:18 PM

Awesome, glad to hear the EHA was the culrpit. That little bugger can do some a number of things to running conditions...I know for a fact it failed me for the smog and the bottom end power was nothing. It would "bog down" then suddenly clear up and accelerate harder after 3k rpm. Even though I was getting 6-7v idle fluctuatin in closed-loop it still did it. After I put in another EHA for the hell of it...the change was like a brand new engine -- completely different. Felt like I gained about 50 ft/lbs of torque LOL!

400Eric · #25 03-22-2010, 02:29 AM

EHA was NOT "the culprit". Read John's posts again:

"Anyways, the new ECU defintely improved things, but something is still amiss. The system is actually going into closed loop now, and the voltage is switching very quickly like it should. I was able to adjust my idle CO mixture, but when you bring the rpms to 2500RPMs it slowly pegs to full rich! 6.5-7.5 volts at idle, bring and hold at 2500rpm and it incrementally pegs to 10.5-11.5V!"

"ECU was the reason I failed emissions just recently, and the EHA was the reason I almost failed two years ago!"

"My theory: My car had a reman'd Bosch FD installed sometime before I got the car. I believe that the EHA had been previously adjusted to compensate for the old FD and they didn't re-adjust it when they installed the new FD!"

The EHA was a factor but it wasn't the main culprit.

It is important to be as accurate as possible as there will be other people referencing this thread for years to come.

Ps2cho, you are bringing your 300TE to our next track day right? Anybody up for some 1/4 mile action?
Regards, Eric

ps2cho · #26 03-22-2010, 03:03 AM

Bad wording...I was referring to just the duty cycle raising up instead of staying within spec after acceleration.

--

Maybe I should! I'm hoping to get her back on the road tomorrow with the transmission back in...Fingers crossed no issues...

JohnM. · #27 03-24-2010, 07:37 PM

It just doesn't want to be fixed.

.

Was going to take it back to emissions on Monday, and checked the duty cycle before leaving. It was all over the map at 2500rpms again!

I also noticed that since replacing the ECU, mileage is in the toilet. I can actually see the gas gauge moving while driving now. I've burned through maybe 1/4 tank, with 60 miles of mostly city driving. Car has never never ever burned this much fuel.

It HAS to be the EHA. Now that the ECU is good, it's actually going into closed loop and the taking into account signals from the EHA. I don't see what else it could be. Back to the junkyards.

JohnM. · #28 03-25-2010, 08:02 PM

Replaced the EHA with a used one, and *drumroll* it's finally fixed. I put the old ECU in, to go driving down to south Denver, so I wasn't burning a crapton of gasoline. Put the new ECU and new EHA in, and it's finally solved.....the 2500rpm reading is now within factory specification with no adjusting needed. There is a reason they say NEVER touch the EHA. It's not supposed to be adjusted, if it's bad or doing weird things.....REPLACE it! And I've also heard lots of people on here say that the EHA is only bad if it leaks externally. WRONG! Mine old EHA didn't leak, and it even tested out fine with a VOM, but was still BAD.

Will take it into emissions testing in the morning, I only have like 2 more days before the car is officially on expired tags, so I couldn't have figured it at a better time. SHEEESH! But quite satisfying...and I spent less than $70 to fix it over the course of the last month. Probably spent close to that on beer alone, trying to figure all this out. HA.

400Eric · #29 03-26-2010, 03:14 AM

Good luck!

JohnM. · #30 03-26-2010, 04:43 PM

Well, as the saying goes, the proof is in the pudding.

.

Took it in this morning, was kind pissed though. There was a huge line, and the car sat for probably 30mins before the test actually happened. Which allowed the CAT to cool down and the engine to go into heat soak. So it was not the most optimal situation. But it still PASSED! I'd imagine these numbers would be even a bit lower with a nice hot CAT. But at least I still retained my OG CAT, not some POS aftermarket! Which is the first thing emissions shops throw at 20 year old cars no matter what.

Latest E-Test (3/26/2010)
HC - 1.3 (Limit 1.5)
CO - 5.6 (Limit 20)
Nox - .094 (Limit 3.5)

Previous E-Test Failure (2/26/2010)
HC - 3.2(Limit 1.5)
CO - 120(Limit 20)
Nox - .024 (Limit 3.5)

First E-Test after Purchasing Car (2/23/2008)
HC - 1.6 (Limit 2.5)
CO - 15.6 (Limit 20)
Nox - .017 (Limit 3.5)

TO RECAP (FOR THREAD POSTERITY)...This is what I replaced. Whereas the O2 and Water temp sensor were probably not bad. But with the O2 at least, it didn't hurt to replace since the old one was...well.....OLD.

-O2 Sensor
-Water Temp Sensor
-EHA
-ECU

Thanks again to all, for your support. If anything, this is just a great place to let off a little steam by ranting about how crappy your car is.