PeachParts Mercedes-Benz Forum - View Single Post

oldtrucker · #1 09-05-2014, 01:38 PM

Been on this one for a while now and think I have exhausted pretty much all leads.
The Car: 95 E320 with 104.992 Gas 3.2L California
Symptom: Idles rough when warmed up and surges at times. Does not do this when AC is on.
Without AC and warm engine. As you approach a red light and put your foot slightly onto the brake at 1-2 Miles per Hour, the engine starts to surge perhaps up to 800-900 rpm's and repeats until the car comes to a halt. Now it idles at 650 and misses ones in a while well I guess every other revolution. With the AC on I can't make out these symptom's.

Vehicle has the California 16 port / pin diagnostics connector.
Error Codes:
DTC:
21 Fuel purge control valve, open or short circuit (more on this later)
26 Transmission Upshift delay switchover valve (Y3/3) without function (more on this later)

Port 8:
13 Throttle valve potentiometer actual value too low.
37 Injection valve cylinder 3, short to positive

1. The Vehicle has the Updated engine wiring harness.
2. The throttle body has been replaced too.
3. Fuel pressure regulator (new)
4. E-Gas Computer (replaced)
5. Purge valve (replaced)
6. Ignition Coils (new)
7. Spark Plugs (new)
8. Throttle Control Cable (new)
9. OVP (new)
10. O2 Sensor (new Bosch)
11. Some Vacuum lines and connector replaced with new lines
12. Mass Air Meter (new Bosch)
13. AIT (new Behr)
14. Air Filter (new)
15. New Oil Dip stick o ring.
16. Cleaned the EGR pipe all the way.

There are probably other things that I replaced, but can't remember each and everything.

The Fuel Purge Valve, I got it from another 104.992 (junk yard) and it worked initially. Thought it got stuck, cleaned it and put back in. No go!
Put it back on the bench and tested it with power supply statically. YES, it does work!
Took a scope to the car and looked at the signal from the ECU. Static at VBatt. Since the ECU seems to switch the return, I checked there. Static VBatt. Seem the ECU doesn't bother to switch it on and off.

Transmission Upshift delay, seems to be similar as with purge valve. Switchover valve works on bench, but not in car. I did an 0815 test on the check valves and I believe that one closes faster than the other one. Vacuum is present and held, I can hear the discharge when I disconnect the lines.

Throttle valve potentiometer actual value too low.
Don't really know what to make out of this. Only a cracked Rheostat could cause a value too low. What is the Computer looking for? If the resistance is Zero, can't get any lower than that. So, it must be some other value it is expecting.
I had CAN BUS communication errors at times, but not recently. Perhaps related to a weak battery?

Injection valve cylinder 3, short to positive, could be my misses, if the valve is really short to positive, would it run rich at 3? or is it lean.
Unfortunately the PO messed up the bolts that hold the fuel rail, I haven't dared to attack this, I think the only way to get them out is with a chisel.
However, I had in the past similar codes on different cylinder? Is the problem travelling?

In an other post, I read that a weak Battery could throw random errors, I find it hard to believe, not knowing the algorithm the ECU goes by, one would suspect several samples before making a decision and throw an error.

I don't want to throw any more parts at the car, although most of what I replaced was more or less necessary. The PO didn't maintain very well and that goes for the front end too.

At this point I see only two more things that could be defective.
Either the battery is weak (don't really believe it) Did another 0815 test on the battery, but have no Idea what the load condition would be. Ignition on, not running. after about 15 minutes the voltage dropped below 12 Volt somewhere to 11.99. Still plenty of energy left to start. Ignition off the battery recovers to 12.4 Volts after a couple of minutes.

Or the ECU has been damaged while the PO was trying to drive with the bad Throttle Body (really bad wiring pretty much all short) I don't want to replace the ECU with another one because of the coding and it could mean trouble during the next smog check.

Someone any more idea's?