2000 911 tiptronics idle RPM issue

Hi, I have a 2000 911 Triptronic. It has about 88k on it and the engine was dropped a few years ago and nearly everything was replaced. A few years ago, we started to have some idle problems, more so, when coming to a stop the idle would drop so low that the oil light would come on. The shop cleaned the fuel injectors and that seemed to help that issue, however I still feel like the RPMs are dropping to low when coming to a stop. Attached is a video, please look at the second rev.... any thoughts would be much appreciated. (And yes, I know I shouldn't rev the engine, but I wanted to replicate the issue).

Clean or if needed replace MAF, followed buy removal and thorough cleaning of throttle body. Both easy to do and will help you rule out common symptoms. Had idle issue (oil light never came on) and did what I mentioned above. Runs like a champ although I just replaced maf as it�s a common wear item. Don�t skimp on maf always buy OEM!

Thank you for the tips. Today I tried the following. I disconnected the MAF. The idle became worse and revving really did almost stall it. I removed and cleaned the throttle body, but it was already pretty clean. I still have the problem. Did my test of disconnecting the MAF prove anything? What else could it be. Thanks, Shawn

Unhelpful response deleted.

Your response is completely unhelpful. I believe in testing before replacing. By your response, you probably replace your car if it doesn't start.

You're right...

fuel pump? if maf has problem, car will run in lamp mode but won't die.

Thanks you for the response. Is there any way I could tell if it is in lamp mode? I don't have any error codes, nor are their performance issues. I am going to add a little bit of back story that I intentionally left out, as I didn't want to skew anyone's suggestions. I believe the car started having this problem after I had to get a new CAT and o2 sensors. The shop replaced them, I got home, and the check engine light was back on. The car was running really really rough and stalling. I took it back, they said they had to re-calibrate the o2 sensors. The car became stable, but the idle still seemed strange. So a few months later when the oil light would flash on.. I took it in and they said the fuel injectors where dirty, they cleaned them. This improved the idle somewhat, and stopped the car from stalling/oil light. Replacing the fuel injectors requires the engine to be dropped, but I am not sure that's really the issue. Could the o2s still need calibration? I am not opposed to replacing the MAF as it is easy to do, but I also don't want to waste money on a part that may have no impact. There wasn't any residue on it. I am just using a cheap ODBII, would getting a PIWIS be of any value? Will I be able to get more relevant information in troubleshooting this problem? Thank you all in advance

For your troubleshooting I would recommend getting the Durametric. It will allow you to read realtime values including the O2 sensors. Also, at idle, disconnecting the MAF sensor and having the engine stumble a bit is normal, but it should not cause it to almost die. But a bad MAF sensor will cause all sorts of idle/running problems. The Durametric will give you the realtime run values for the MAF sensor. You said you cleaned the throttle body. Did you remove it and clean it? Bad idle can be caused by a clogged up Idle Control Valve which is on the throttle body. Is your throttle body drive by wire, or e-gas? And finally, no, O2 sensors do not need "calibration". They either work right or don't work right. The DME uses the O2 sensors for feedback on how the engine is running (rich/lean/cold/hot), so if you are not getting a CEL and codes for bad O2 sensors (there are 4...2 pre-cat and 2 post-cat) then it is probably not bad O2 sensors. That being said, our cars are highly sensitive to the correct O2 sensors. What type and part number O2 sensors did they put in? Same goes for the MAF sensor. Don't get some cheap sensor if you go that route. My MAF sensor looked perfect...cleaned it several times and finally gave up on it. Replaced with a new Bosch MAF sensor and all was well again.

DBJoe996, Thank you for your response. Any chance you can help me out and provide a link do a Durametric ( http://www.durametric.com/modelfeatu...ixv6.aspx#996) , what to make sure I get the right one. I don't know the O2 sensors.. it was an indy shop, I am looking for a new shop though.. I did remove the throttle body, and it was pretty clean on both sides, however I didn't disconnect the idle control valve. it is e-gas. I have attached a photo, it isn't my car, but it is the exact throttle body I have.. so maybe I am an idiot and didn't remove and clean enough? I took the 4 bolts out and cleaned both sides. maybe I don't know where the ICV is? Now thinking about it.. I am not 100% sure there was the rubber gasket on the throttle body :/ Please pardon my ignorance.

You have an e-gas throttle body. No idle control valve. Idle is controlled by the DME. Before doing anything else do an e-gas calibration - turn ignition key to ON, wait 60 seconds and turn key to OFF. You will hear clicking and whirring from the TB. And, there should be an O-ring between the TB and intake plenum. If it is missing, that will cause a massive air leak, and of course very poor idle/running. If you don't remember it being there, good idea to check again. That is correct for Durametric. When you order, what you get is a cable that connects to the OBDII port and a USB port on your laptop. Always download the most recent version of the software from the website.

On the throttle body remove the silver clips holding on the black plastic cover. Inside you will see the same slot car style brush over circuit that the toys have. With a q tip and some maf or Tb cleaner run it along that track. You�d be surprised how much carbon buildup gets on there. Also it�s a good time to apply some silicone lube to plastic gears. Also anytime you mess with maf/Tb make sure you do an egas resetto recalibrate throttle mapping. The car with mag removed won�t immediately show anything as the computer is still mapping as if it was installed. The engine needs to run awhile before ecu compensates for its removal.

Take the car to any automotive store like auto zone and they will do free obd scan. Write down the numbers and report back.

Thanks for the information, I do appreciate it. I will doublecheck the O-Ring. I could be insane, and it could have been there.. I will try cleaning the and lube the gears. I can tell you that every normal shop here will only pull the CEL codes, and since there are none, it doesn't do me any good to go to a shop. Is there a way to tell if the TB is bad? If I know replacing the TB and the MAF would fix the issue, i'd overnight the parts :-)

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If either was bad a scan would pick the faults up. Try the autozone free scan.

Go slow. As stated earlier, the MAF sensor should be considered a wear item. I would do the work you have outlined, then get a new MAF sensor and go from there. Since there are no codes, it is difficult to pinpoint the problem(s). So go one step at a time.

Hey all, It is too hot for me to work on the car today, but we did drive it, and something curious happened. When cold, she starts up fine and idles fine. When warm, you can see the tachometer bounce a little, in my opinion, when warm, the idle is low (maybe 650-700 RPMS), So, now the issue. We drove about 20 miles and parked. I went into one store, my wife into another. I went to move the car closer to the other store after about 20 minutes. Car started fine. When we left the other store, 10 minutes later, the car started, idles rough and stalled. We restarted the car, it was idling rough, as if it was going to stall, I had my wife give the car some gas. The car then resumed its normal idle. Does this point to something else? Or do you all still think it is the TB/MAF? Thanks again for all your help!

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What is that supposed to mean?

Did you do the e-gas calibration? Sounds more and more like you will need to put in a new MAF sensor. If you do, at least that will eliminate that as a suspect.

Yes, the e-gas calibration was done. I will order a new MAF and start from there.

As I suspected, replacing the MAF has no change in the idle, behavior was exactly the same. I re-ran the e-gas calibration, but the problem still persists. Any other ideas? I have a PIWIS cable on they way.

How about the fuel filter/dirt in the tank? I had a similar problem with a boat many years ago. There was dirt in the fuel tank which would be in the bottom initially but would get churned up while underway.

I will be honest, I haven't checked that. I would have thought that the shop would have checked that when they did a cleaning on my fuel injectors; but now my impression of the shop is different. So let me ask this, aside from just replacing it, is there a way to test it? We don't notice any issue with performance other than at idle, or even starting it. If the engine is cold, the idle is above 1k, and everything is good, it is only when it is warm at it drops to 750 (well it drops lower). Thanks again, Shawn

The more I think of it, the less I think this is the case. If it was dirt/bad filter you would notice an issue at all speeds, not just idle.

Vacuum leak? Leak in exhaust between O2 sensors? Leaking fuel injector? I am hoping that the PIWIS will give me actual values to locate issue. It just means a lot of googleing for what is "normal" Could the throttle body valve not been closing fast enough? or too fast?

I just found this: https://rennlist.com/forums/996-foru...e-issue-5.html Originally Posted by kj217 after all,, issue solved by replacing the fuel tank breather valve,, it wasn't releasing air when pressure builds up in the tank,, which was causing instant fuel cut-offs,, the whole thing cost $200 @ the dealer,, Now to find the fuel tank breather valve.......

Glad you have a plan. Nice find!

Really stupid question... I know it will throw the CEL most likely; but couldn't I test that theory by leaving the gas cap off? Otherwise I need to jack the car up, remove the tire, etc