Engine check light on after service - thanks for your help

[Ahsai]

What is the MAF reading at idle? I think it should be 15-17kg/hr (at least for the 996s). Looks like it's under-reading the real flow so the DME has to add so much fuel to correct it. Also, what intake air temp it reads? Do you have any air leak e.g., cracked oil filler tube.

[jmaier]

So I noticed something, I cleaned the MAF again but to no avail. Reading at idle no load shows 28kg/hr which is too high.

We had a cold morning and when I started the car it died, restarted and the IDLE was unstable but it remained on.

Another thing I noticed: I opened the oil filler tube when the engine was running. I could open it without issue but there is definitely a vaccum (I can both hear and feel it). Is it normal to have some vaccum from the oil filler, again, I could remove the cap without difficulty but the vaccum is definitely present.

THank you,

J

[Ahsai]

J, a slight vacuum at the oil filler tube is normal. The engine should also shudder a little bit and the idle rasied to compensate for the air leak with the cap removed.

Was the 28kg/hr measured when the engine is cold and fast idling? If the MAF is over-reading the air, the DME should remove fuel (negative fuel trim) though, which is not consistent with your +25 STFT. The 15-17kg/hr number is when the engine is idling AFTER its fully warmed up. Sorry I should have specified that.

Sounds like a bad MAF or air leak after the MAF to me.

Edited October 7, 2013 by Ahsai

[jmaier]

I took the reading warmed up. What's interesting is that when I wrote about the error codes and stft above, the MAF value were around 18! I checked the 1095 error code details this time and the stft were both at 0 and ltft at +3!! So it seems that I have very different results from one reading to another.

Is this leading more toward a leak or MAF in your opinion?

[Ahsai]

I hope JFP will chime in soon.

Can you check the following when the engine is idling rough and fully warmed up and no a/c load?

These are the nominal values for 996s but yours shouldn't be drastically different, especially if yours is also a 3.6L and not 3.8L

If the MAF reading was truly 28kg/hr under the same condition, I think the MAF will be the suspect. Also have you removed the airbox and verified there's no obstruction in the air passage that may throw off the MAF reading?

Idle speed 680 rpm +/-20

Mass air flow 17 kg/h +/-2.5

Hot film mass air flow meter 1.3 V +/-0.2

Range 2, cylinder 1 - 3 (FRA) 1.02 +/-0.04

Range 2, cylinder 4 - 6 (FRA 2) 1.03 +/-0.05

Range 1, cylinder 1 - 3 (TRA) 0.00 +/-0.1

Range 1, cylinder 4 - 6 (TRA 2) 0.00 +/-0.1

Missfire counts on each cylinder

Also another thread with the same code http://www.renntech.org/forums/topic/40523-error-code-p1095/

Edited October 7, 2013 by Ahsai

[JFP in PA]

Chiming in...............I would concur that looks like there is a vacuum leak in the system and it is struggling to try to adapt for it.

[Ahsai]

Thanks, JFP. Hope J has more to go on now.

[jmaier]

Ahsai, you seem to lean toward MAF and JFP towards leak?

MAF reading is definitely high 29 warmed up and without load.

I decided to try a new MAF, it all started right after I change the airfilter and cleaned the MAF with MAF cleaner. It would be a weird coincidence that the day I clean it a leak occurs (I did not remove any hose or weird stuff).

I will receive the new MAF tomorrow. Do you advise me to disconnect the battery before swapping? For safety and also reseting the ECU?

I will let you know the result!

J

[Ahsai]

Hi J,

This one is diffcult without more data hence I asked for more sensor readings in Post #30.

P1095 and 29kg/hr points to the MAF - however, if MAF is truly over-reading, the STFT should have been way negative instead

+25% STFT suggests air leak after MAFand it contradicts the above - you did clean the throttle body so you must have removed the air box and the fat rubber intake connected to the throttle body

I guess if you're sure you don't have any air leak after the MAF, a new MAF is the logical thing to try. I agree disconnecting the battery will be the safest before installing the MAF. You just need to wait/drive longer for things to readapt before you can conclude whether it does fix the issues.

Good luck and do let us know.

[Ahsai]

Oh btw, have you tried wiggling the wire/connector of the MAF when the engine is idling rough and see if it improves? This is to test if the MAF connectors/harness has loose contacts.

[jmaier]

Hi All,

so I received the new maf. Disconnect the battery, swapped the maf, validated that all error codes were gone.

I went for a drive, the car ran smoothly, idle not perfect but better. No issue.

I come home, plug in the durametric and the P1095 is back in the list!

Mass airflow ahead of throttle body, implausible.

Occurred are 28% load

54kph

2800rpm

Ambient air temp: 27C

Intake air temp 40C

But here is where it's interesting:

STFT and LTFT: 0 on both banks. I went for a 20 mile drive.

I'm almost giving up, I have an appointment on Tuesday at the dealership but if anybody has a last idea I'd love to hear it. I double checked the wiring and connection of all hoses as well as proper fitting of the tb. All looks good...

THank you!!

[JFP in PA]

At this juncture, it is entirely possible you have a DME error; let Porsche look at it.

[Ahsai]

That's frustrting! By STFT and LTFT, I assume you meant FRA and TRA numbers? Indeed very strange if they are all zeros after a 20 mile drive. Let us know how it goes.

[jmaier]

Yes it is!!

I mean short term and long term fuel trim as recorded in the fault code.

I will let you know the outcome, I fear the bill!

THank you for your help!

J

[Ahsai]

Hopefully it's just a loose wire/connection between the DME and the MAF.

[jmaier]

OK so the dealer just called me. They suspected a vaccum leak and proceeded with a smoke test. Apparently the leak was at the "intake boot". Can you guys tell me which part that is? I can't figure it out! My understanding is that it's the connector right after the MAF to the throttle body is that right? In that case, I don't know how I could have missed it!!!! :cursing:

Bottom line is that they were fair, charged me with 1h diagnostic and that's it!

[Ahsai]

Yes, it's that round fat rubber tube with pleats between the MAF and the throttle body. Did you check the pleats (top and bottom) carefully?

http://www.qsm.com.au/accessories/997intake_3155_1024.jpg

[JFP in PA]

OK so the dealer just called me. They suspected a vaccum leak and proceeded with a smoke test. Apparently the leak was at the "intake boot". Can you guys tell me which part that is? I can't figure it out! My understanding is that it's the connector right after the MAF to the throttle body is that right? In that case, I don't know how I could have missed it!!!! :cursing:

Bottom line is that they were fair, charged me with 1h diagnostic and that's it!

Don't be hard on yourself, sometimes small spits or cracks are difficult to find on these connectors, even the pros miss them.

[jmaier]

and the cel came back. About 2 hours after leaving the dealership, idle started acting up again and the cel light came on. Same code, same behavior :-(

[Ahsai]

I think JFP was not kidding when he said even pros can miss things....It's not clear how they fixed the problem. Did they replace the intake boot or they showed you the leak?

I suspect intermittent connection issue on the MAF if it's not air leak.

Edited October 18, 2013 by Ahsai

[jmaier]

They did not replace the boot and I did not have time to have a look but when I go back I'll have a talk with the technician directly.

Thanks Ahsai, I'll call the dealer and let them know to check the connection (if they haven't already done it on their own)!

I'll report back on the issue.

J

[jmaier]

Interesting update: the dealer finally identified the issue to be the throttle body. Their porsche master mechanic pulled 2 tb out of engines they had on end and tested my car successfully.

Now what I find interesting is that the very first code I reported on this thread using an autozone reader was: p2102. Explanation is "throttle actuator control motor circuit low". This code seems actually more to the point and accurate than the code returned via the durametric.

Any thoughts on this?

[JFP in PA]

Interesting update: the dealer finally identified the issue to be the throttle body. Their porsche master mechanic pulled 2 tb out of engines they had on end and tested my car successfully.

Now what I find interesting is that the very first code I reported on this thread using an autozone reader was: p2102. Explanation is "throttle actuator control motor circuit low". This code seems actually more to the point and accurate than the code returned via the durametric.

Any thoughts on this?

You could be having an intermittent TB servo fault which goes away, along with its code. I have full faith in the Durametric system software reading the correct codes, but it also cannot read what is not there when it is plugged in.

That said, I would also ask the Porsche "master mechanic" what codes he saw with the PIWIS that led him to replace the throttle body.

[Ahsai]

Agree with JFP and I'll wait till you personally tested the car before making conclusions :)

[jmaier]

I finally got the car back yesterday and it runs perfectly! As a summary of my issue and warning to whomever wants to clean his throttle body:

After servicing the car including throttle body clean up, my car started idling very badly and I received the following error code:

P1095: Air mass ahead of throttle valve

After many trials and trips to the dealer, they found 2 issues:

1. Minor air leak on the air intake boot

2. MAF was not damaged, we tried with both a new one and the old one

3. I get the car back after this and the faulty code comes back after 1h and IDLE is again erratic

4. GO back to the dealer, performs more tests, and finally decides to try to get a throttle body from a same engine that they had in the shop

5. Tests were conclusive and the TB was changed. The car runs like new.

When I cleaned the TB, I removed it completely and cleaned the inside of the tube and moved the plate to thoroughly get all the oil out (not much but I wanted it super clean). Apparently when forcing the plate to move, I damaged the position sensor.

Thanks all for your advice and support!!!