I'm soooo rich!

[CBRacerX]

My mixture that is...

3.6 transplant car. 1998 993 Euro Electronics. Car started running so rich that, well, it won't run.

I've changed the AFM, Head Temp Sensor and 02 Sensor. No joy. Any suggestions on what else could be causing this? I suppose a leaking injector is possible, but is there another possible cause?

Thanks!

Chris

[Lorenfb]

The possibilties are:

1. shorted (to ground) injector harness
2. shorted injector driver in the DME unit
3. a damaged DME unit causing injector driver "on"
4. bad ground connections to DME unit
5. bad fuel pressure regulator

Check out this web site (www.systemsc.com) on the Diagnostics page under No Start.

[CBRacerX]

Some additional details that might help prospective helpers:

This car was running A-OK until about 2 weeks ago.

The engine harness and DME harness are NEW (not just new to me, but NEW from Porsche).

I haven't tried a DME swap, but that might be on the short list. I am willing to check the wiring from the various DME sensors to the DME (which I did when I got the new harness and installed it) but I'm not optimistic there.

Anyone?

Chris

[Lorenfb]

Hopefully, you didn't get water into the DME unit, a real bad problem.

You need to use a test light and check that no injector is continuously "on".
Next, make sure that the sparks (both) are good. If you disconnect
the AFM, you'll minimze the fuel being injected assuming no continuously
"on" injector.

The 964 DME units are very reliable as indicated on my web site (www.systemsc.com)
on the Failures page. They basically never fail.

[911mot]

What about an exhaust leak upstream of the O2 sensor - making sensor richen engine...

[CBRacerX]

Mot - The exhaust system is tight as a drum, although that is a good suggestion. If I run the injection on the default map (without the 02 sensor) the problem still exists.

Loren- it is _possible_ that the DME got wet a few weeks ago. I had the windshield replaced, and then got to drive an hour in a fierce rainstorm that revealed the installer didn't do a great job. I had moisture on the carpet in front of the DME, but not a drastic flood. Still, there is a possibility of some sort of water damage, and the problem evidenced itself at just this time.

If the DME is water damaged, what are the options? I can probably confirm this by making a temp swap with a unit from Steve Timmins. If I need a repair/replacement, are there any options you could suggest?

This is the DME (before any potential damage occured). Is this a standard Bosch version used on other vehicles that I could swap in? I hope so!



Happy New Year!

Chris

[911mot]

I assume its making the plugs wet, getting a spark, but still not starting.
In that case I would suspect the timing has gone awol. Perhaps due to crank sensor failure or loose / bad wiring.

[CBRacerX]

No, the vehicle starts and runs, but poorly. Both distributors are working fine, spark is A-OK. This is a overly rich (very over) condition only.

Cheers,

Chris

[Lorenfb]

"This is the DME (before any potential damage occured). Is this a standard Bosch version used on other vehicles that I could swap in? I hope so"

Yes, it's the standard '95 993 unit. Any early ('95) unit will work. Check out the part numbers
on my web site (www.systemsc.com) on the Parts page.

You need to dry the unit out if it did get wet.

[Speedster94]

hallo
Chris
You have a problem with the Heater from the Lambda Sensor , it is connected with the Enrichening Fuel for Coldstart . Once it has temperature the System shuts the WUR and the Heating off. Usually there is a Cable under the seat , from the DME harness Green /black you need to soldered to black/red on the 14 Pin Plug in .
I am sure about the Green/ Black but check on the Black/red as i cannot see it in my Speedster without taking the seat out .
It is 10 PM here so i can check in the shop tommorow . But this is the Problem .
Hartald

[CBRacerX]

Harold - Thanks for the reply! I have tried the system with both a three and four wire 02 Sensor. Since the wiring harness I am using is an option M150 (leaded gas), it doesn't have the wiring for the heater on the sensor. However, I have wired the heater independently (to a switched ignition source) and this was working for about a month. I would like to add the appropriate wiring to the correct DME plug to get the heater controlled by the DME, so that it is not always on. The wiring diagrams I have seen show the heater hot line coming from the 55 pin DME plug.

Loren - I'll pull the DME tonight and see if there is any obvious water damage to it. I'm surprised that the '95 993 DME (US version hopefully) can operate the Varioram when the appropriate harness and chip are installed.

Thanks!

Chris

[Speedster94]

chris
The WUr is not shutting off , i think . The old DME can operate the Varioram as you have a resoncevalve on the older Engines too .
But the original varioram opens at 3800 RPM and about 6000 RPM .
The normal only at about 5000 RPM
Harald

[Lorenfb]

"The WUr is not shutting off , i think ."

What is this?????

The 993 Motronic system doesn't use a WUR nor does it use an AFM.
It uses a MAFS.

Where is this thread going?

[CBRacerX]

I've got the DME out, and it looks perfect. I had a different chip installed vs. the picture, and the paper label on the chip is spotless. In my install, the chip side of the DME is facing forward, so I would expect to see some water damage there is the DME got so much as damp - it didn't to have been touched. Of course, looks mean very little with electronics! So now I will try and arrange for another DME to get swapped in.

Chris

[CBRacerX]

Just to be clear, this is a '98 varioram unit, with a new Euro M150 option DME harness (variant resistor removed) and a new 993 engine harness. It has been running well for two months after installation. Only recently has it developed an intermittent over-rich running condition, which gets bad enough to shoot flames out the exhaust and kill the engine under 3K rpm. I've swapped the MAF unit, the 02 Sensor and the Head Temp sensor with not good luck. The problem has gotten so bad that the car is no longer driveable.

I think Harold is referring to the "Warm Up Regulator", which is this case is a program mode of the DME used to run the car when cold. I agree, this is the symptom, but I now need to somehow fix this issue. A DME swap is my next debugging step, although I do not have a DME to try at this time. Do the fine folks at SystemSC have a compatible one on the shelf?

Thanks!

Chris

[mede8er]

I am currently experiencing this.....car ran fine then started running rich....switched DME's but no change...starts and idles fine but will not idle when driven...

[CBRacerX]

Mine had gotten so bad that #4 was "always on".

Your symptom is interesting, it won't idle after being driven? I guess it is possible that this is O2 or AFM related.

Have you run this past Dr. Timmins?

Chris

[CBRacerX]

How about Head Temp Sender? That could certainly be the culprit!

[mede8er]

I've ruled out the head temp sensor by putting a variable resistor in the loop set at about 95 ohms....should 'trick' the DME into warm run mode.....

This is freakin crazy and driving me insane...gotta be something simple I'm overlooking.....

[CBRacerX]

Next step is AFM then.