Hey Geoff - checked the values - appears the O2 sensor is OK. When the engine is cold, then started, the O2 sensor starts at 0.44V. It remains at this voltage for 38-40 seconds, then it went to 0.42V. From that point on, the voltage continued to drop - I assume as the sensor began to heat itself up. After about 2 minutes the voltage was slowly dropping to about 0.20V - it was not yet oscillating to the higher value. Since the car was in the garage, I started to smoke myself out so I stopped the engine after the couple minutes.

Looks like the O2 sensor is OK... it seems like I might have an intermittent sticking injector?

 

Garrett376,
Ok thats that out of the way , maybe. I would next check the lamda heater element.Its the two black wires on the probe .Pretty low resistance , not open circuit.
Then check that you have battery power to the wires with the motor running.
The slow creap down ,assuming the heater is ok, is indicating a lean mixture ,
so unless you have a heavy misfire with one injector off , forget injectors for now.
I seem to remember that the flap volts at idle were OK , about 1.0 volts.
Been suggested before but with the ECU getting the correct stuff, next issue is air leak. Look real close at everything on the inlet manifold cross pipe . As a check pull hoses of and blank .
We will get there !!
All the best,

Geoff

 

This may be way off base, but I saw a thread recently where someone found an air leak around the intake manifold by spraying (I think) carb cleaner at the base. Is that possible? He indicated that WD40 would not be good to spray. I'm way out of my element here, but thought this might trigger some brighter minds to trouble shoot an air leak on the intake manifolds.

Cheers,
Dave

 

Geoff, you're the man! Thank you for contributing and helping me sort this out, I greatly appreciate it. This forum is the best

If I had an air leak, why does the error code come back that the mixture was rich? I do see that Test Point 21 in the workshop manual vol1 mentions that air leaks will cause this error to appear. Hmmmm. That's my next stop - pull apart the intake to check out the seals (too bad I didn't look while the engine was out 1 month ago!!!!).

 

Again I recommend before you start ripping things apart that you check the vacuum reservoir below and behind the air box. Check the connections on the reservoir and just follow the lines around the engine bay. It is possible something has just fallen off. Seeing as the engine was only installed a month ago, this is a possible cause. There is a t-piece with two or three connections depending on if you have the headlight adjusters fitted by the air intake. I have seen this come apart on numerous occassions.
I have seen cracked air intakes as well, but only on 964s with the plastic intakes.
You might also want to check the vacuum connection to the reasonance valve solenoid and the valve itself.
Ciao,
Adrian.

 

Garrett376,
The lamda probe will respond to the exhaust gases it sees. Lean mixture-low volts , Rich-high volts. This way you have your own mixture indicator!
Normally , the ECU will see the lamda volts going low and try to richen up the fuel. Then it goes too rich , high volts and the ECU winds the fuel off , etc,etc.
That is why it is called closed loop-keeps going round in circles !!

I sometimes have "closed loop " days !

If you have dash headlight height adjust disconnect the small hose and plug it .The diaphragms in the lights split giving a vacc. leak.
I would think that this is a relatively big leak so maybe check out big hoses first ?

Geoff

 

dfinnegan, I don't know Porsche vac leaks (yet) but on "other" cars, spraying Carb cleaner around intake seals etc. can help locate a leak. It's combustable and will raise the RPM slightly if you find a "hole".

I would hesitate to spray carb cleaner on pcar parts until someone else (with more knowledge)chimed in on it. Carb cleaner is corrosive and can melt/dissolve some plastics. For example, some GM fuel injection units don't mix well with carb cleaner.

 

Mark,

Thanks for the clarification. I also did a bit of searching and found a reference to leak detection using propane (post #3).

Cheers,
Dave

 

How do you say "KA-BOOOOOM"

 

Yeah. The whole process of spraying anything into the engine makes me nervous. I wasn't even all that comfortable about spraying water looking for arching on my wires!

Cheers

 

But I love ripping things apart! Just kidding - thanks for the tips Adrian - starting simple is definately the way to go. By the way, if I'm not online to tell you, Merry Christmas and Happy Birthday this Sunday!

I am heading to Utah for some snow... so no updates on my progress for a bit. Unfortunately, the C4 won't be our transport - the trusty ML320 with seat warmers gets that job

 

Garrett376,
I have heard a ML320 called a lot of things but never "trusty " before!!!!!!!!!!!!!!!!
Have a good Christmas and get back rested and ready to fix this problem !!!!

All the best

Geoff

 

Hi Guys - a long time overdue, but I came across this post of mine from a couple years back: a new O2 sensor fixed the problem!!! Odd despite the normal readings I had with the Hammer...

And Geoff, the ML continues to be "trusty"!!!

Happy New Year everyone!

 

Thanks for the update Garrett. How did you figure out it was the O2?. Andy

 

I figured since the sensor tested out of range a few times with the Hammer; then I came across a good deal on the O2 sensor online, and this sensor was one of a few things I had not yet "gone through" in sorting my car.