John Speake

Many of these "mysterious" problems can be solved with the aid of a diagnostic tester. Yes, this is a sales pitch for my version of the "Hammer"..........see my web site.

http://www.jdsporsche.com/jdsdiagtool.html

A tester has its own limitatations of course, but it can short circuit much wasted time and expenditire on unecessary parts...........

Several 928 owners in a local area could share the cost and have the tool available as required.

Rich is correct about the various modes of LH failure, often the ECU "thinks" the WOT switch is always open although the fault is the ECU itself. This richens the mixture all the time etc etc.

T_MaX

Hey John, I didn't know you had your tester done!

Thats great, have you had a chance to compare it to the "Hammer" yet.

If it does the same, your spot on as far as time savings!

John Speake

Thanks Kurtis,
It's not identical to the Hammer, my website details the differences. The unit hardware is capable of everything the Hammer does......I just need some revenue to fund more software development. I have spent about $15,000 on software already :-(

Software upgrades will be available to purchasers as I get them developed. Also other Porsche models will be catered for. All the fault codes are written already.

Jerome Craig

Bill,

Check the setup on the emissions test machine. I'm right down the street from you and the places I've gone to have different "Limit" readings. Here's my numbers and dates:

8/20/04 Burke Center Exxon

15 MPH

Limit Reading Result
HC 118 193 Fail
CO 0.66 2.57 Fail
NO 905 405 Pass

25MPH

HC 114 166 Fail
CO 0.70 3.38 Fail
NO 824 244 Pass

10/12/04 Ox Road Exxon

15 MPH

Limit Reading Result
HC 118 386 Fail
CO 0.66 7.72 Fail
NO 905 272 Pass

25MPH

HC 114 364 Fail
CO 0.70 7.38 Fail
NO 824 269 Pass

Luckily I have known the gentleman who owns the maintenance part of Ox Road Exxon - Dave for a long time. Dave asked if his tech - Jimmy could take a look at the car to see if he could get it to pass the emissions test. I've known Dave for 13 years and he's seen my car for 12 of those years - so the moment of truth was at hand. On the one hand at close to 250K miles the car has only had three different techs work on it - one for the past nine years! On the other hand Dave has always maintained my other cars and has always done a better, more thorough job than many dealers.

Bottom line - I let Jimmy have a look at it. A couple of hours later Dave called with the news. The oxygen sensor wires were completely corroaded and shorted out. I got on the phone with Dave Roberts @ 928 Specialists - got an O2 sensor way below dealer price - had it delivered to Dave and Jimmy. A couple of exhaust hangers bushings and a fuel injector flush later, my numbers were:

10/21/04 @ Ox Road Exxon

15 MPH

Limit Reading Result
HC 118 11 Pass
CO 0.66 .05 Pass
NO 905 569 Pass

25MPH

HC 114 13 Pass
CO 0.70 .11 Pass
NO 824 389 Pass

The number at Ox Road Exxon is 703-273-3822. Dave will more than likely be there. Send me a PM and we'll chat over the weekend.

Randy V

Hey John S -

I've been waiting to see your post introducing your new diagnostic tester.

Wassup?

Bill Ball

Cool. I'm interested.

John Speake

Hi Randy - I sold out of my first batch of diagnsotic testers very quickly, and am havng a second batch made now. I expect to be able to deliver in about 2 weeks.

I was waiting until I could give a firm delivery date before "launching " it officially :-) Probably during next week.

Bill, thanks for your interest, I've replied to your mail to my website.

bgrabner

John Speake - you're a Brit - what is a good British slang for idiot? I finally was able to start looking closer at this problem, and come to find that my O2 sensor was disconnected inside the passenger footwell. The PO had an aftermarket cell phone setup in the car, wired into the stereo, so wires were running everywhere, including in and around the fuse block. While pulling that crap out several months ago, I guess I inadvertently pulled the O2 connector apart and never reconnected it. Dumb, dumb, dumb...I still have to get the car re-tested tomorrow, but it definitely didn't help the sensor do its work if it never was getting any power . I will post the results of the test is tomorrow.

Thanks to all of you!

Bill

SharkSkin

See pic below:

John Speake

LOL !! yes, there are lots of other Anglo-Saxon names for all of us who drop the odd "clanger"........

Dave, it looks like the picture was taken "oop north " ?

Ok Bill, glad you found a good reason for the problem :-(

You will need to drive the car around for a few miles to get the system to "adapt" to the new conditions. the you should pass that emission test with no problems............

regards

bgrabner

OK - very strange. Failed try #2, but only barely:

15 MPH
HC ppm: Limit=103, Reading=3 PASS
CO %: Limit=0.58, Reading=.01 PASS
NO ppm: Limit=778, Reading=776 PASS

25 MPH
HC ppm: Limit=100, Reading=2 PASS
CO %: Limit=0.61, Reading=.01 PASS
NO ppm: Limit=709, Reading=984 FAIL

So how could reconnecting my O2 sensor bring my HC and CO in line, but throw my NOx out of whack? Granted, it didn't do it by much, but it looks like I am running pretty lean. Could I still have a faulty O2 sensor? Stranger still, since reconnecting my O2 sensor my idle stumbles a bit - not bad, and not constant, but ever since I replaced the MAF w/ the O2 sensor apparently disconnected, my idle had been rock steady. I guess my next step is to go ahead and replace the O2 sensor and see what affect that has. Anyone have any thoughts?

Bill

John Speake

Hi Bill,
The car will need to adapt the O2 loop to the system. Did you run the car for some miles under various conditions ?

Having said that, it does certainly appear to be running very lean, even taking into account th airpump being connected...

can you check the O2 sensor voltage ?

Bill51sdr

Bill,

The NOX failure is being caused by the fact that the engine is running so lean now as John stated. This is a fairly common occurrance with 928's from what I've seen in this forum, mine was very close on NOX as well. Probably due to the high compression of these engines and the fact that Porsche uses valve overlap to control combustion chamber temps instead of an EGR system. Like John said, check the output of your O2 before you just replace it. Should be getting rapid changes between .2 and .8 volts as was stated at the beginning of this thread. If you still can't get a pass on the next test, you may want to try a good fuel injector cleaning service or additive before you try again. Every little bit of fuel counts in this case. Good luck!

bgrabner

John S. - yes, I ran the 928 for about 20 miles at varying speeds with the O2 sensor re-connected prior to the 2nd test - didn't change the stumbling idle at all either.

John and Bill - I just pulled apart the O2 sensor connector and tested the connection - with the car warm and idling, my voltage is steady at .5v - I am not getting rapid changes in the voltage, not even with the swinging idle. I re-ran the car a few miles with the O2 sensor disconnected, and it is still idling poorly, although the car is pulling strong. If my voltage is steady, does that mean there is a loop problem? How would I fix that? Could it be the Injection Brain going as JE suggests?

I guess my bigger concern (and frustration) is the idle problem now - since the only change made was reconnecting the O2 sensor, I just can't see how that would affect my idle speed?

I am thinking that since I have an O2 sensor that Tom Falkenberg loaned me, I should just put that in to remove any possibility of the sensor being the issue - its a PITA I know, but then many things on this car are - isn't that what makes this fun?

Thanks all for the continued help...

Bill (Twatt)

bgrabner

One more thing - if I am running lean, could that cause problems with my idle speed? Like the engine isn't getting enough gas to run steady at idle? Just a thought...