996 3.6 idle issue (with codes)
Discussion
Hi Guys,
I have an issue with the idle on my 996 3.6 02 manual. Although only fractional, the idle hunts between 670-725 rpm, with the tacho needle wavering in the dial and an unsteady wobble noticeable through the seat when sitting in the car.
The problem is not present when the car is cold (first thing) and has the higher idle speed, but when warm the hunting problem comes and goes. The car never looks to stall, and doesn't drop lower than 670rpm or higher than 725rpm.
What I have done so far to try and cure this:
1) Changed all plugs and coil packs
2) Changed air filter
3) Cleaned inside of throttle body (no black gunk to report) and searched for leaks and splits in the trunking between the airbox/MAF and throttle body
Sadly those efforts have not made any difference though. In any other car I would be replacing the Idle Speed Control Valve or similar, but these later 996s don't feature this kind of unit?
The DME will on the odd occasion (and it can be weeks in-between occurrences) throw the following error codes. I get all these codes or none, and always as this "set". When it does happen they usually illuminate the engine light when crawling in slow traffic, within the first 5 minutes of the journey, when the engine is under 2000rpm, so no real load. If I clear them from in the car they will not occur again for the rest of the journey, or for several journeys later (the car is my daily). The codes I get "as a family" each time are:
P1109 "Input variables, Charge Measurement"
P0300 "Misfire Detection"
P0304 "Misfire Cylinder 4"
P0305 "Misfire Cylinder 5"
P0306 "Misfire Cylinder 6"
The only symptom is the slightly fluctuating idle and the subtle shake through your bum on the driver's seat. The car drives superbly well, is very smooth, produces power as it should and has great MPG. I realise that whatever situation is making those error codes occur could be entirely linked to the slight idle speed hunting, or not at all related and another random issue to fix just occurring in parallel!
So, can Pistonheads please help me with my Porsche woes? Why is my idle not rock steady? What are those error codes all about?
Thanks,
Chris
I have an issue with the idle on my 996 3.6 02 manual. Although only fractional, the idle hunts between 670-725 rpm, with the tacho needle wavering in the dial and an unsteady wobble noticeable through the seat when sitting in the car.
The problem is not present when the car is cold (first thing) and has the higher idle speed, but when warm the hunting problem comes and goes. The car never looks to stall, and doesn't drop lower than 670rpm or higher than 725rpm.
What I have done so far to try and cure this:
1) Changed all plugs and coil packs
2) Changed air filter
3) Cleaned inside of throttle body (no black gunk to report) and searched for leaks and splits in the trunking between the airbox/MAF and throttle body
Sadly those efforts have not made any difference though. In any other car I would be replacing the Idle Speed Control Valve or similar, but these later 996s don't feature this kind of unit?
The DME will on the odd occasion (and it can be weeks in-between occurrences) throw the following error codes. I get all these codes or none, and always as this "set". When it does happen they usually illuminate the engine light when crawling in slow traffic, within the first 5 minutes of the journey, when the engine is under 2000rpm, so no real load. If I clear them from in the car they will not occur again for the rest of the journey, or for several journeys later (the car is my daily). The codes I get "as a family" each time are:
P1109 "Input variables, Charge Measurement"
P0300 "Misfire Detection"
P0304 "Misfire Cylinder 4"
P0305 "Misfire Cylinder 5"
P0306 "Misfire Cylinder 6"
The only symptom is the slightly fluctuating idle and the subtle shake through your bum on the driver's seat. The car drives superbly well, is very smooth, produces power as it should and has great MPG. I realise that whatever situation is making those error codes occur could be entirely linked to the slight idle speed hunting, or not at all related and another random issue to fix just occurring in parallel!
So, can Pistonheads please help me with my Porsche woes? Why is my idle not rock steady? What are those error codes all about?
Thanks,
Chris
Not from experience, but some thoughts:
Inlet air leaks need to be checked down stream of the throttle body too as this is where the vacuum on idle will be greatest. Of course this is a pita... Vacuum pipes well worth an inspection.
A misfire on one bank is detected by the o2 sensor for that bank I assume? Could it be a leak on the inlet of that bank ie inlet manifold leak?
Inlet air leaks need to be checked down stream of the throttle body too as this is where the vacuum on idle will be greatest. Of course this is a pita... Vacuum pipes well worth an inspection.
A misfire on one bank is detected by the o2 sensor for that bank I assume? Could it be a leak on the inlet of that bank ie inlet manifold leak?
LotusAlfaV6bloke said:
I hope not, they were both changed by Porsche 17k miles ago.
I suppose my question is whether a faulty variocam solenoid make the idle speed wander fractionally? Would it explain the P1109 Charge Variable error code?
Open to learning all I can!
The misfires are confined to just one bank. This does suggest a problem with the VarioCam system on that bank.I suppose my question is whether a faulty variocam solenoid make the idle speed wander fractionally? Would it explain the P1109 Charge Variable error code?
Open to learning all I can!
When what proved to be a VarioCam solenoid/actuator failed on my 2002 Boxster the short term fuel trim for the affected bank was quite erratic. At the dealer I mentioned this to the tech and he said it was the DME adjusting fueling trying to get the desired O2 sensor reading. The tech said that in some cases the fueling can get so far afield that the engine can misfire.
In your car's case, while the solenoids were replaced the problem could be the actuator. In the case of the Boxster and I think this is true of the 996 engine as well, there is no way to determine if the solenoid or actuator is bad. The tech told me the SOP is to replace both items, at least on the Boxster.
As an aside, with the 996 the solenoid is rather easy to get at and one can replace the solenoid and if the symptoms are gone that's just great. But if the symptom are not gone, or come back, this points to the actuator and then it must be replaced.
However, for some reason the tech replaced just the solenoid. I was not given the opportunity to ok or decline a replacement of the actuator, which I would have had replaced based on what he had told me, and what I had heard from other experienced techs. Just a day after getting the car back with the new solenoid the symptoms appeared again and the car went back in and the actuator was replaced. The dealer service department ate the duplication of labor and hardware (new camshaft cover bolts for instance) as the SM knew I would have ok'd the replacement of the actuator at the same time as the solenoid was being replaced. I still had to pay for the actuator but most of the labor cost was assumed by the dealer.
There is also -- back to your car again -- there is also the possibilty the new solenoid is bad. This is why there is a warranty offered on new parts.
But an intake leak could possibly be the problem. At least this possibility has to be eliminated before digging in deeper.
BTW, you are reading the active codes, but are there any pending codes? When my Boxster's solenoid/actuator was acting up there was no CEL and no active code but there was a pending code -- P1341 -- and this code pointed to a problem with the solenoid/actuator.
I really appreciate your help - I think our last messages crossed over at the same time! I was trying to show my fuel trims and Lambda readings.
I see that the solenoids are MUCH easier to change on the 3.6 compared to 3.4, but the actuators are still very hard to get to for both engines?
I can't find anyone aside Porsche themselves to source the solenoids from, any clues Pistonheaders? Design911 is coming up with nothing.
I hate buying replacment parts that may or may not be related to the fault, especially as the acuators are quite costly!
I see that the solenoids are MUCH easier to change on the 3.6 compared to 3.4, but the actuators are still very hard to get to for both engines?
I can't find anyone aside Porsche themselves to source the solenoids from, any clues Pistonheaders? Design911 is coming up with nothing.
I hate buying replacment parts that may or may not be related to the fault, especially as the acuators are quite costly!
I have seen similar faults caused by a sticking switchable tappet. The test for those is to start the car from cold and leave it idling; after approx 120 seconds the tappets will switch from high to low lift (the valve lift is set to high for the cold start to encourage gas flow at low temperatures). If one or more tappets doesn't switch correctly the idle will become lumpy (as the fuelling is reduced to match the low lift but the resultant weak mixture is felt as a misfire). If the car isn't left to idle during the switchover the issue can remain elusive as the tappets complete their switching process better at higher engine speeds.
Do the start test and see if the misfire is repeatable.
Do the start test and see if the misfire is repeatable.
Thanks - Ill give this a go and report back.
One thing - regardless of whether I leave it to idle or simply drive off, after 2 minutes the "lower idle" is achieved anyway because I think the car will be up to temperature?
Therefore, if I let it idle for 2 minutes and the idle drops to the normal lower speed but it is a but "floaty", is there a way of knowing this is due to an air leak in the manifold (for example) or the tappet issue you describe?
One thing - regardless of whether I leave it to idle or simply drive off, after 2 minutes the "lower idle" is achieved anyway because I think the car will be up to temperature?
Therefore, if I let it idle for 2 minutes and the idle drops to the normal lower speed but it is a but "floaty", is there a way of knowing this is due to an air leak in the manifold (for example) or the tappet issue you describe?
Although I started this thread ages ago, the problem reappeared and I have just fixed it.
I have changed the solenoid for that bank (the one nearer the front of the car) and the problem is completely solved! No leaking inlet manifold, no complicated issues with the engines internals... just a duff solenoid.
When I removed the original one the little spring on the end was deformed, and the connectors on the plug were less than perfect. A replacement with new seal and some contact cleaner on the plug has made my idle rock solid. No more engine light coming on at 2000rpm after a few minutes of driving each time!
The lesson is.... the first response on here is often all you need!
The part I used was 996 105 301 03 (4) "camshaft actuator"
It is quite easy to fit as on the later 996 3.6 engines these are outside the bank. If you can change the coil packs and plugs on this bank, you are competent enough to change this solenoid.
Such a cheap fix, I am very happy
I have changed the solenoid for that bank (the one nearer the front of the car) and the problem is completely solved! No leaking inlet manifold, no complicated issues with the engines internals... just a duff solenoid.
When I removed the original one the little spring on the end was deformed, and the connectors on the plug were less than perfect. A replacement with new seal and some contact cleaner on the plug has made my idle rock solid. No more engine light coming on at 2000rpm after a few minutes of driving each time!
The lesson is.... the first response on here is often all you need!
The part I used was 996 105 301 03 (4) "camshaft actuator"
It is quite easy to fit as on the later 996 3.6 engines these are outside the bank. If you can change the coil packs and plugs on this bank, you are competent enough to change this solenoid.
Such a cheap fix, I am very happy
Having just got my 996 C4S, I was interested in why the idle needle fluctuates ever so slightly at idle - it hardly moves, just a tiny constant flicker of perhaps 25 to 50rpm
I read this was normal, but your original post seems to indicate that it can be an indicator of a wider issue or perhaps just if it gets a bit more erratic?
I read this was normal, but your original post seems to indicate that it can be an indicator of a wider issue or perhaps just if it gets a bit more erratic?
Jefferson Steelflex said:
Having just got my 996 C4S, I was interested in why the idle needle fluctuates ever so slightly at idle - it hardly moves, just a tiny constant flicker of perhaps 25 to 50rpm
I read this was normal, but your original post seems to indicate that it can be an indicator of a wider issue or perhaps just if it gets a bit more erratic?
Factory manual gives an idle speed of 740 +/- 40 RPMs.I read this was normal, but your original post seems to indicate that it can be an indicator of a wider issue or perhaps just if it gets a bit more erratic?
Before you look for any problems try an E-gas calibration. The steps to do this should be in the owners manual. Probably something like this: With the ignition key off and your foot off the gas pedal the entire procedure turn the key on and leave on for at least 60 seconds. After at least 60 seconds turn the key off. Leave off for at least 10 seconds. The next time the engine is started the calibration is complete.
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