M119 - low power off idle - help! (W124, 500E)
 

OK, so I figured it was time to start a thread about my low power problem, mentioned elsewhere a few times. A little background data is here, if you're interested:

http://500ecstasy.com/forums/showthread.php?t=14&page=4

Anyway, here's the latest scoop:

The car (1994 E500), when at operating temp, won't spin the STOCK tires from a stop in first gear. I have the BergWerks FGS and ASR defeat. When warm (85-90C on the dash gauge), 75F ambient temp, if I punch the gas from a stop it just takes off - no wheelspin (with ASR defeated), or no engagement of ASR (with ASR active).

When the car is cold (just reached 60C on the dash gauge), it will light up the tire(s) pretty easily, and spin all the way to the redline in first, then hooking up during the shift to second. When warm, forget it. Nada.

Here's what I've done. New plugs (old ones were very worn) - no change. New OE air filters - no change. Pulled LH module for 15 minutes to re-set (several times) - no change. Was using Sinclair 92 octane (pump decal says 'with 10% ethanol for cleaner air'). Added 2 gallons toluene to half tank of that gas, for nearly 20% mix - NO CHANGE. I even re-set the LH module again after putting in the rocket fuel. I drove around for 30-40 miles to make sure the rocket fuel was mixed and into the engine, still no change. Usual ambient temps are in the 70-85F range, elevation is 2400ft above sea level. (Side note - when I got home I popped the hood and was looking around while the engine was running, and noticed it had an intermittent miss at idle, that I don't recall being there before... grrrr. Also seemed less than perfectly smooth when held at ~2000rpm, but I'll need to compare to when it's cooler.)

Some WAG's: Top end power *seems* OK, since it will pull to the top speed limiter, and 1/4 mile trap speed is good (95mph) considering the weak launch. I wonder if the cam adjusters aren't adjusting? They're supposed to advance (?) cam timing in the low/mid RPM range to boost power. No idea how to test that. I guess I could do a compression test for grins, but it doesn't smoke, burn a lot of oil, or seem low on peak power so I was assuming that's not likely to be the issue.

So now what? It's embarassing (and depressing!) that stock 400E's can whip me at the dragstrip...

:( :( :(

Have you tried pulling the LH module out?

Maybe at one point in time one of the previous owners used low-octane fuel and the engine got used to it?

I was about to do that to mine but I didn't have the hex keys to do it.

Yup. Did that before adding the octane booster (toluene), and again after adding the octane boost. I pulled the LH module and left it out for a good 15 minutes before re-installing.

:(

What does taking the module out accomplish ?
Battery disconnect does not clear memory on stock LH module.

Arthur,

The public consensus has been that pulling the LH module out of the CAN box re-sets it. Is that not true? If so, how do I re-set it? BTW, it has the stock/factory chip in there, AFAIK.

:)

Do you have a 38 pin connector and a led/sw set-up?

Just a hunch. Did you measure the fuel pressure? Injectors good?

Arthur - not that I know of, and I need a little help deciphering your question... ;) I'm a diesel guy, this is my first M119!


Shane - Good question. I believe that had been checked (by the PO, while diagnosing a different issue) and deemed OK.


BTW, I'm running a simultaneous thread on this over on the 500 forum, there has been some interesting comments from Carl over there:

http://500ecstasy.com/forums/showthread.php?goto=newpost&t=810

:o

I took that LH module out, used "Quick Detailer" to go over some parts of the car and put it back in.

No difference - still slower once the engine is hot. One thing for sure though it doesn't do the same when the weather's nicer (i.e late at night when it's not quite 80*F outside)..

and in winter it's really powerful all the time :D - not even a 5.0

ps. I made myself feel good about the M119 by driving a Passat 1.8T.. :p

I have seen articles where , for racing performance, guys
substitute a resistor in place of the Air Temp sensor.
They get the resistance value by measuring the sensor when the temp is at 60C and use that value. [ The sensor is a thermistor and changes values according to temp- this, in turn, effects both the a/f ratio and the ignition timing. The higher the temp, the leaner the a/f and the more retarded the ignition ]
This is supposedly when the ECU mapping is the strongest due to the rich settings. Once the car is at factory running temps, they run lean and don't have the performance of the lower temps.
May want to check the inlet air temp sensor values .
I don't have that info at hand, but Jim F web page might.

I understand that the ECU retards the timing when the engine coolant temp reaches a certain temp, which I believe is an anti-knock feature.

I do know for sure that mine has always had a crisper throttle response from a stop in cool weather compared to hot weather.

Anti Knock is simply retard when pinging occurs. [ usually from octane ratng/load][
The actual timing curve mapping is not controlled by knock sensors...they are just a safety feature that retards the ignition
under adverse conditons..[ie-knock/ping]

Dave -

First of all, I have absolutely nothing useful to offer here.

Second, when did you get the 500E? I'm so jealous! I occasionally kick myself for not picking up a nice example that was available locally last fall.

- JimY

I mis-spoke. I realize there is a separate anti-knock circuit, complete with knock sensors in the engine block.

I can't quote anything more specific other than my own vague recollection, but I have read in several sources that the M119 engine, at least, does alter (I assume retards) its timing when coolant temperature exceeds a certain value.

I'm simply saying that this engine is designed such that it is not as "peppy" off the line when the weather's hot. I always look forward to cooler fall weather for just that reason...

<<I'm simply saying that this engine is designed such that it is not as "peppy" off the line when the weather's hot. I always look forward to cooler fall weather for just that reason>>

SW
I certainly agree with your observation ..
I think the main reason for the lean burn design is that the auto companies are all looking for max mpg to compete in market share..
..but I can see that the lower ambient temp [as seen by the air temp sensor] would result in better performance, as the engine is running at better power .
I guess that is the theory of fooling the ECU management by using a resistor the value of the Intake sensor at lower temps.
...ie-richer /longer injector durations.