Morpheus Posted 4July, 2021 Report Share Posted 4July, 2021 Hello all, I have a misbehaving 996. Has developed symptoms where she wont idle - keeps hunting revs (between 1000-1900rpm) like I'm warming up a race car motor.. Did it a few times then stopped but now does it all the time, even after she is warmed up... It is as if the choke is stuck on or there is a vacuum issue somewhere. I'm going to take her to Buiks but I wondered if anyone else here with a 3.4 has had similar issues. 996 - 1998 3.4 with about 160k on the clock. Driven on weekends only and serviced late last year (they said the AOS was leaking and tightened the clamp on one of the lines). Its bloody embarrassing as it sounds like I'm a hoon at the lights - I have stopped driving her which I hate because what's the point... Quote Link to comment Share on other sites More sharing options...
TwoHeadsTas Posted 4July, 2021 Report Share Posted 4July, 2021 3 hours ago, Morpheus said: Hello all, I have a misbehaving 996. Has developed symptoms where she wont idle - keeps hunting revs (between 1000-1900rpm) like I'm warming up a race car motor.. Did it a few times then stopped but now does it all the time, even after she is warmed up... It is as if the choke is stuck on or there is a vacuum issue somewhere. I'm going to take her to Buiks but I wondered if anyone else here with a 3.4 has had similar issues. 996 - 1998 3.4 with about 160k on the clock. Driven on weekends only and serviced late last year (they said the AOS was leaking and tightened the clamp on one of the lines). Its bloody embarrassing as it sounds like I'm a hoon at the lights - I have stopped driving her which I hate because what's the point... Suspect might be plug packs? Should show up on scan tool? I was going to suggest might also be sticking variocam actuators, but unless I'm mistaken (quite possible!!) variocam not introduced until the 3.6L in the 6.2 911CSR 1 Quote Link to comment Share on other sites More sharing options...
911CSR Posted 5July, 2021 Report Share Posted 5July, 2021 First step would be to get am OBD2 diagnostic done. If you can get hold of a Durametric (IMHO the best ODB2 scan tool) or another scan tool you could see what error codes are being thrown if any. I had a similar issue with my 996.2 and after checkign with Durametic, it turned out to be an AFM sensor which was a $150 and 10 minutes with a torx bit to fix. AFAIK, typical issues for poor idle on a 3.4 could be: 1: As mentioned by @TwoHeadsTas, coils and/or plugs. 2: AFM/MAF sensor failure - usually associated with an ABS / PSM failure. Can try to remove and clean with proper AFM cleaner (Supercheap etc. sell this one) see if it resolves ($20 and 10 mins to exclude or see if it makes a difference). 3: Idle control valve blocked/failed - if stuck open /blocked can cause lean running, inspect and clean. 4: Air/Oil seperator failure - intake post throttle very oily. Replace AOS (pain is the A** to do but common issue) 5: Vacumm leak due to cracked hose etc. - hard to run down, but visual insprection of hoses is a good start for crack or poor connection 6: Fuel system - If fuel pressure is waivering, pump or fuel filter could be on the way out or blocked. DT 1 Quote Link to comment Share on other sites More sharing options...
flamingporsche Posted 5July, 2021 Report Share Posted 5July, 2021 1 hour ago, 911CSR said: First step would be to get am OBD2 diagnostic done. If you can get hold of a Durametric (IMHO the best ODB2 scan tool) or another scan tool you could see what error codes are being thrown if any. I had a similar issue with my 996.2 and after checkign with Durametic, it turned out to be an AFM sensor which was a $150 and 10 minutes with a torx bit to fix. AFAIK, typical issues for poor idle on a 3.4 could be: 1: As mentioned by @TwoHeadsTas, coils and/or plugs. 2: AFM/MAF sensor failure - usually associated with an ABS / PSM failure. Can try to remove and clean with proper AFM cleaner (Supercheap etc. sell this one) see if it resolves ($20 and 10 mins to exclude or see if it makes a difference). 3: Idle control valve blocked/failed - if stuck open /blocked can cause lean running, inspect and clean. 4: Air/Oil seperator failure - intake post throttle very oily. Replace AOS (pain is the A** to do but common issue) 5: Vacumm leak due to cracked hose etc. - hard to run down, but visual insprection of hoses is a good start for crack or poor connection 6: Fuel system - If fuel pressure is waivering, pump or fuel filter could be on the way out or blocked. MAF sensor as first port of call. Easy win if this is it. Everything else is time & $$... Quote Link to comment Share on other sites More sharing options...
Fishcop Posted 5July, 2021 Report Share Posted 5July, 2021 My coil pack failure certainly gave similar symptoms as you've described - do you have a Check Engine Light (CEL) displayed? Coil failure throws the CEL up on the instrument panel. As suggested, grab some form of OBD tester. Durametric is the go, but I got one of the iCarsoft Por V2 units for $250 which reads all the general OBD codes as well as Porsche specific codes - it will also clear your codes once you've fixed the issue. Hopefully it's one of the minor issues these cars get and is just a weekend fix. Merv 1 Quote Link to comment Share on other sites More sharing options...
Merv Posted 5July, 2021 Report Share Posted 5July, 2021 I also have the iCarSoft which can be used in the car without computer interface. It does sound like a coil pack prob but could also been O2 sensor. Read those codes or it is just expensive guess work. Quote Link to comment Share on other sites More sharing options...
911CSR Posted 6July, 2021 Report Share Posted 6July, 2021 I just realised I have an iCarsoft ODB2 that you can use or buy as I also have the Durametric and don't really need the iCarsoft anymore. Quote Link to comment Share on other sites More sharing options...
Morpheus Posted 7July, 2021 Author Report Share Posted 7July, 2021 Thanks so much guys. I will try these out this weekend and report back - fingers crossed. I have a Bosch oBD2 scanner - haven’t tried it on the 996 so will try that first. No CEL and the throttle body is as clean as new. Quote Link to comment Share on other sites More sharing options...
DT Posted 7July, 2021 Report Share Posted 7July, 2021 My money would be on the AOS if you’re at 160km and it hasn’t been replaced and is leaking, it’s well past it’s use by. Merv 1 Quote Link to comment Share on other sites More sharing options...
Merv Posted 8July, 2021 Report Share Posted 8July, 2021 The AOS is not expensive and a must do item. Quote Link to comment Share on other sites More sharing options...
Morpheus Posted 26September, 2022 Author Report Share Posted 26September, 2022 Didn't realise I hadnt come back and posted what the issue was... So after leaving it for a while I (long enough to need a new battery 😕) Ifinally got time to take her to Buiks. Guys there found that the airbox must have not been closed properly or a bump had opened it and hence a vacuum leak... New battery and some labour and she was good to go again! I ended up doing a AOS sometime later and also changed the waterpump as the bearing started to get quite noisy. Just need some decent weather now to get her out more often... sjm, JWM, 911CSR and 2 others 5 Quote Link to comment Share on other sites More sharing options...
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