DME Actual Values

[jcorallo]

1997 Boxster 2.5 UK spec (RoW). 69,000 miles. 5sp manual gbox.

I'm trying to diagnose the cause of some part throttle hesitation and cold start stall issues I'm having.

Note that the MAF is brand new as are the Lambda probes.

I've got the Durametric tool and there are no DTC's stored at all.

So I was looking at the actual values after I took the car for a spin and got it all warmed up.

Here are the actual values. First col is the component, second col is the expected value taken from the Boxster DME diagnostic manuals and last col is the actual value I got with the Durametric. I've highlighted in red font the values that were not in spec:

Any thoughts from you experts?

Also, what is Segment (A) and Segment (B) a measure of ?? What does this being out of spec tell me?

Any help much appreciated.

Cheers,

Jules

Edited March 13, 2007 by jcorallo

[Richard Hamilton]

Jules

Just found this in the DME manual:

2 Read out learning progress of sensor wheel adaptation.

1. Connect Porsche System Tester 2.

2. Select vehicle type 996, DME, Actual values.

3. Select Segment A, Segment B, Learning

progress of sensor wheel adaptation.

When the values of segments A and B are around

zero, e.g. 0.0003, adaptation is complete.

The value of learning progress must then be smaller

than 0.0005.

If the value of learning progress remains at 1.0000,

the flywheel is defective.

If the values of segments A and B are also at 1.000,

then adaptation has not yet been performed.

In this case, perform a test drive with three deceleration

phases in the speed range from 3000 to 1400

rpm.

Hope it helps. Hopefully someone will be able to comment on the actual values.

[jcorallo]

Hi Richard,

Thanks for this - the values you quote are all different from what I'm seeing and what my manuals tell me they should be...

It makes me wonder if maybe the Durametric is mis-reporting the values in the DME for segments A and B ?? Given that they appear to be a factor of 10 out either way, if you see what I mean??

However, at least I now know what the values are meant to represent - its to do with adaptation - which is good to know at least.

I wonder why your manual mentions the flywheel with regard to adaptation ????

Cheers,

Jules

Edited March 13, 2007 by jcorallo

[Glyn]

Hi Richard,

Thanks for this - the values you quote are all different from what I'm seeing and what my manuals tell me they should be...

It makes me wonder if maybe the Durametric is mis-reporting the values in the DME for segments A and B ?? Given that they appear to be a factor of 10 out either way, if you see what I mean??

However, at least I now know what the values are meant to represent - its to do with adaptation - which is good to know at least.

I wonder why your manual mentions the flywheel with regard to adaptation ????

Cheers,

Jules

Keep at it Jules, I can see you are not going to give up on this one, After 4 years with the 2.5 i never found the cure (as you know) until now ---I bought the S.

I will continue to follow your progress - best of luck mate

Glyn

[tholyoak]

have you checked to see that the idle valve is not gummed up and therefore not regulating your idle speed? This would also create a static false air source resulting in the low value for your MAF readings.

Todd

Edited March 13, 2007 by tholyoak

[jcorallo]

hi,

I removed the idle air control valve at weekend and it was clean - no oil or gum.

I did notice two clean scrape marks on the door section which I assumed were normal, like tracks?

Cheers,

Jules

[tholyoak]

But does the door move freely when you apply light pressure with a screwdriver? Does the idle change when you unplug it with the car running?

Todd

Edited March 13, 2007 by tholyoak

[jcorallo]

I didnt touch the swing door but I did unplug it with the engine running and it almost stalled out, then regained after a short while and idled happily without it, assume it was using ignition to keep idle. A DTC was then stored which I cleared.

Jules

[jcorallo]

I'll take the valve off again this weekend and double check that its OK - its quite quick to do this.

I've also asked Durametric to check the Actual Values reported by their tool for Segments A and B. I'll report back when I hear anything.

Jules

[insite]

can you post your fuel trims?

[tholyoak]

can you post your fuel trims?

He did. they are the range 1 (idle) and range 2 (off idle) values in his table. The off idle value on bank 2 is a bit out of spec, but only slightly. That coupled with the low MAF reading and the high idle may suggest a minor false air source somewhere.

I had a problem with an idle valve where the engine would start and stall several times before it would continue to run, once running it was fine. The idle valve seemed to operate correctly physically but after I replaced it with a new one the problem stopped. Upon closer inspection it seemed that the little door mechanism seemed quite loose so I assumed it was just worn out and unable to properly function. I also had a completely gummed up one where upon removal it simply wasn't moving. In this case the car had a hard time starting when cold since the idle valve was essentially frozen in an open position. The idle speed would steadily increase as the car warmed up, as you might expect.

In either case I never had a check engine light.

Another question I have, since the fuel trims are only a bit off on one side is what is the condition of the plugs?

Todd

[insite]

He did. they are the range 1 (idle) and range 2 (off idle) values in his table......

Another question I have, since the fuel trims are only a bit off on one side is what is the condition of the plugs?

thanks; hadn't reviewed a durametric output before. plugs is a thought. vacuum leak on that side of the motor is another thought. use propane or carb cleaner to search for a vacuum leak.

[jcorallo]

Jules

Just found this in the DME manual:

2 Read out learning progress of sensor wheel adaptation.

1. Connect Porsche System Tester 2.

2. Select vehicle type 996, DME, Actual values.

3. Select Segment A, Segment B, Learning

progress of sensor wheel adaptation.

When the values of segments A and B are around

zero, e.g. 0.0003, adaptation is complete.

The value of learning progress must then be smaller

than 0.0005.

If the value of learning progress remains at 1.0000,

the flywheel is defective.

If the values of segments A and B are also at 1.000,

then adaptation has not yet been performed.

In this case, perform a test drive with three deceleration

phases in the speed range from 3000 to 1400

rpm.

Hope it helps. Hopefully someone will be able to comment on the actual values.

Hi Richard,

It says above that vehicle is 996, not 986.

Do you have any information on these values specifically for a 2.5L RoW 986 with the DME 5.2.2?

Or does this information still relate to my car do you think?

Can you let me know the title of the manual you are using, and maybe send me a snapshot of that section from the manual, please?

Cheers,

Jules

[Richard Hamilton]

Hi Jules

This was taken from the 996 OBDII Manual for DME 5.2.2, relating to P0300-P1319 misfire fault codes. I think it would also apply to your car as it is the same version. I just checked the 986 Manual, but it doesn't have that part in it. I'll email you the info - I just thought it may be useful for determining what Segment A and B mean, which I kind of assume relate to the adaption (learning) of the flywheel position sensor - just my guess.

[jcorallo]

Thanks Richard, I've got that now.

tholyoak and insite - thanks - yes I'll be having a look to check for leaks. Although I'm wondering which side of the engine to look at because my VAG-COM / HEX-COM generic OBD2 scanner give the following Long Term Fuel Trims (LTFT):

Bank 1 LTFT = -2.5%

Bank 2 LTFT = -4.8%

I'll be checking this again because the above values were only 1 day after I had reset the DME - I need to let the DME adapt so I'll post up again when these values seem to settle.

With regard to the condition of the plugs, its the first thing I checked and changed as a matter of course. Note that the change of plugs had no effect on running.

I've kept the plugs in numbered boxes so I'll double check tonight that there is nothing out of the ordinary, but they all looked the same from memory and in very good condition - which is what I guess I should expect, given that the DME has adapted so that both sides of the engine are running according to the Lamdba requirments. There was deff no oil or contamination on the plugs either.

Cheers,

Jules

Edited March 15, 2007 by jcorallo

[insite]

Bank 1 LTFT = -2.5%

Bank 2 LTFT = -4.8%

check these every time you drive the car as it adapts. if they continue to drift negative, it's your MAF. eventually, the car will starve for fuel when you lift off the throttle. the computer will try to compensate with an STFT correction and breach the rich threshold, throwing a code. confirm this when your CEL comes on at a stop light (my gut says it will when your adaptation is complete).

once this happens, unplug your MAF and go for a drive. your throttle hesitation issue should be cone, as the DME goes to a default fuel map when it senses an open MAF circuit. this will confirm the bad MAF.

Edited March 15, 2007 by insite

[jcorallo]

The MAF and both pre-cat Lambdas are brand new - just installed last week....

[insite]

The MAF and both pre-cat Lambdas are brand new - just installed last week....

i know, but so far, your adaptation process is leading me to believe that you may still have a problem there. we'll wait until it completes to further diagnose.

[jcorallo]

Yep no probs - its a slow process!

Update on the Durametric - I got an email saying they think there is a problem in the reporting of the Segment A and B values which they looking at - they compared the Durametric with a PST2 on four of their own DME's.

They believe both values are meant to read as 1.0 when adaptation is complete. This is different from what Richard above said as his manual says they should be zero when adaptation is complete.

So the jury is out on this at the mo....

Cheers,

Jules

[insite]

They believe both values are meant to read as 1.0 when adaptation is complete. This is different from what Richard above said as his manual says they should be zero when adaptation is complete.

So the jury is out on this at the mo....

use the generic OBD II tool again; it should tell you 'readiness' status. if all is OK, adaptation is complete and we can begin to diagnose again.

[tholyoak]

My understanding of Segment A and B are they are involved in the DME adaptation/learning process and dictate the amount of time in two different driving segments. The fact that these values are not at there stipulated value seems to suggest that you have not put the car through enough driving cycles such that the DME adaptation/learning progress is finished. This would mean that the fuel trims etc will change until the OBD readiness status is achieved.

The fact that your fuel trims continue to change suggest that the adaptation of the DME is not complete yet and comparing the output actual values to the expected values may not be too informative.

Todd

[jcorallo]

OK I think adaptation is complete now.

My generic OBD2 scanner gives readiness as go:

readiness

The fuel trims reported in the OBD2 scanner are still the same as stated above.

Here are some screen shots of Durametric Actual Values. This is with a hot engine at idle:

actual_values1.jpg

actual_values2.jpg

actual_values3.jpg

actual_values4.jpg

actual_values5.jpg

Naturally some of the above values are moving around (e.g. O2 reading/ RPM etc) but the adaptation ones which are of interest TRA/TRA2 FRA/FRA2 are stable.

The FRA2 is just within spec now - the ideal value is 0.96 plus or minus 0.03. It was 0.92 before I reset the DME and tried again. I guess it will drop further in time below 0.93 though...

Jules

[insite]

The FRA2 is just within spec now - the ideal value is 0.96 plus or minus 0.03. It was 0.92 before I reset the DME and tried again. I guess it will drop further in time below 0.93 though...

it looks like the car is trying to lean itself out above idle and then allow the mix to richen at idle. this indicates a car that is likely a bit starved for air at engine speeds above idle; at idle it seems to get enough air. check your air cleaner. check for vacuum leaks on the secondary air injection system. also, it technically could still be your MAF. let it run for awhile without a DME reset and see if it throws a code. in the meantime, check the stuff i mentioned above.

[jcorallo]

Hi insite,

Yep will do - thanks for the pointers. I suppose it could be a clogged air filter, but will check for leaks as you suggested.

Also note that since this is a 1997 RoW model, there is no secondary air injection. It also very rarely throws a code since its pre-OBD2 compliant. It certainly does not throw a code as its running now.

Cheers,

Jules

Edited March 16, 2007 by jcorallo

[insite]

Also note that since this is a 1997 RoW model, there is no secondary air injection. It also very rarely throws a code since its pre-OBD2 compliant. It certainly does not throw a code as its running now.

well that certainly makes things a bit more complicated! can you describe the throttle hesitation bit as best you can? does it happen from a stop? from any constant speed to acceleration? on decel? this is a manual trans, correct?