dkcaims

Wideband O2... next to the stock narrow band O2.

dkcaims

Cleaned the terminals on the CHT plug and let it run for 2 minutes.
Ran no better... resistance measured at the sensor plug = .342k ohms
Can't measure at pin 43 on the DME plug, it's empty.

Makmov

its ohms by temp. That is an okay reading at 80C

Sorry the tiny numbers got the best of me. pin 45

Indycam

Do you have a decade resistance box ?
Do you have multiturn vr / Multiturn potentiometer ?

If you do you can swap one in for the cylinder head temp sensor and dial it up and down while watching the a/f readout .

A bad cylinder head temp sensor can do what your car is suffering from .
I bought my van for $200 because the smog tester said that the motor needed a rebuild .
I replaced the chts and it passed the smog test at the same shop that said it would not without an engine rebuild .

The sensor can fail altogether and cause the motor to go bad or the sensor can start to go bad and the motor will start to run poorly .

dkcaims

No I don't, but I'll see if I can borrow one.
Thanks for the information.

dkcaims

Ruled out the AFM... It's reading .25 volts closed to 4.5 volts fully open with no dead spots.
The search continues.
I'll spend the day and clean up all the ground points tomorrow (oops it's already tomorrow).
I'll wait til daylight !

dkcaims

Today...

Fixed a leak where the blower goes into the intake.
Confirmed AFM is within spec and working properly.
Confirmed PSC1 is working properly, proper signals are getting to the DME.
Cleaned up 8 ground points, 4 under the bonnet, 2 in the engine compartment, strap underneath car, and one under the drivers seat.

...but problem still remains.
I'm running out of ideas !
DME was checked a couple months ago and was working fine. Have not had it checked since this problem started last week.

So to recap...
Starts immediately, does not surge, idles smoothly, but AFR's go from 14.7 to 10.5 after about 15 seconds and stay there.
It's looking like the Porsche Parade will be missed if I can't fix this soon.
Anyone have any suggestions? My tech is booked for the next 2 weeks.

Could it be spark related? I would think if it was, it would not start easily or run as smoothly as it does.

Indycam

If you unplug the cylinder head temp sensor , does it run just the same same ?

dkcaims

There is a momentary surge but then just the same, yes.
The resistance was measured and seemed within spec, but I'll give it a shot.
It was last replaced 62,000 miles ago.

Makmov

Yeah, does NOT sound spark related.

dkcaims

... that's good.

I guess that means I honing in on the problem, albeit by process of elimination.
You going to Porsche Parade Christopher?

dkcaims

Something I noticed this morning...
Since I repaired the leak between the intake manifold and the pipe coming from the blower, the manifold pressure is indeed a bit higher based upon my MAP sensor in the PSC1.
Hypothesis...
If the fuel pressure regulator has a damaged diaphragm, fuel can be sucked into the manifold through the vacuum line, is that not correct? Thus, increasing the AFR's
Before I repaired the intake leak it took 10-15 seconds for the AFR's to start falling from 14.7, but now it's much quicker, just a couple seconds after starting.
Could the increase in manifold pressure and quicker drop in AFR's be pointing to a bad Fuel Pressure regulator, or am I grasping at straws?


The fuel pressure gauge is reading 51-55psi still.
DISREGARD !!!
Unplugged vac line from regulator, same problem. Oh well...

Makmov

I would sure like to, not sure if I can though.

dkcaims

Well... installed new CHT sensor this morning. Still running rich 10.3-10.5 AFR at idle = no change.

darth

Other than the AFR readings, is there any other indication it is running rich? Does the car perform differently?