986 S - Hunting type idle when hot😬

[Triops]

Please help!

Car starts fine. Smooth acceleration , good power, but when hot it idles with a surge and then almost dies I think it’s called ‘hunting’. Idle when cold is fine. It has cut out a couple of times at low revs on a turn, but not regularly. 
No coolant leaks, no oil usage

I have fitted new plugs and coil packs cleaned the throttle body and a new Bosch MAF today.

No change still an uneven idle when hot. 

Any one had similar issues and solved it successfully? Maybe I can sort it myself .Maybe not🤔

 

[the baron]

You have an air leak somewhere, you will need to take it to a good Indy to have that checked.

[Triops]

Yes, some have suggested crank sensor. I think it’s off to the local Porsche people. 

[femreg]

23 hours ago, Triops said:

Please help!

Car starts fine. Smooth acceleration , good power, but when hot it idles with a surge and then almost dies I think it’s called ‘hunting’. Idle when cold is fine. It has cut out a couple of times at low revs on a turn, but not regularly. 
No coolant leaks, no oil usage

I have fitted new plugs and coil packs cleaned the throttle body and a new Bosch MAF today.

No change still an uneven idle when hot. 

Any one had similar issues and solved it successfully? Maybe I can sort it myself .Maybe not🤔

 

I have the similar issue, I did all cleaning over the weekend, because they told me your car pass MOT emission with very low margin. Mine is like like as you mention but the both cold and hot, I don't have stable idle or while driving 1st gear without pressing anything car is not smooth. What else we need to check if there is no air leak?

[cdm]

Check that the oil filler pipe is well sealed by removing the cap and feeling for suction by putting your hand over the top of the pipe. I had a crack develop in the bendy pipe from the rear bulkhead to the engine giving air leak and hunting idle speed. It can be a bit of a struggle to get the hose clip off on the bulkhead end if you need to replace it....

 

 

[Triops]

Typically people mention a crankshaft sensor plug and the Air / oil separator. 
Both of these are doable if you can get under the car. Good advice is to get ‘101 Projects for your Porsche Boxter’ by Wayne R Dempsey as soon as..

[Triops]

Apparently one of my variocam adjusters is not working properly on bank 1 May be bank 2 as well. Not ideal but they have both been disconnected = even tick over. I can’t pick up a performance loss but I’ve only had the car 10 months and it’s probably always been an issue. If I drop the engine at any time I will fix this. My independent Porsch guys talked big money (to fix). Engine drop plus dealing with rusty manifold bolts etc. i am going to see what happens. Maybe done 200 miles since with no apparent issues. 

 

[map]

6 hours ago, Triops said:

Apparently one of my variocam adjusters is not working properly on bank 1 May be bank 2 as well. Not ideal but they have both been disconnected = even tick over. I can’t pick up a performance loss but I’ve only had the car 10 months and it’s probably always been an issue. If I drop the engine at any time I will fix this. My independent Porsch guys talked big money (to fix). Engine drop plus dealing with rusty manifold bolts etc. i am going to see what happens. Maybe done 200 miles since with no apparent issues. 

 

My understanding of a deactivated variocam system is that it sticks in the low rev range which gives a smooth idle and low engine speed pickup. The downside is that this is at the cost of performance further up the  rev range.

The advice I heard around deactivated variocam was to check cam deviation - think you need the Porsche or Durametric diagnostics for this. 

[TROOPER88]

Relatively common and I was going to suggest this at the time. I decided not to as it can be a costly repair.

 

A failing variocam solenoid or actuator on one bank will cause hot idle issues and a lack of overall power (circa 20% down). Depending what engine you have, it can be fixed in situ but you are still looking at a 1k job.

Fault code would likely: P1341

I had a customers in recently with this fault. I had other work to do on that particular car but I did not to the solenoid, it was done at La Rose. 

[Triops]

It has been suggested that an ongoing controlled performance drive for an hour or so getting h engine really warmed up might restore the activators to health. The test would be to reconnect them both directly afterwards. There seems to be divided opinion on whether you have to drop the engine to fix or not (2001 3.2S)

[Triops]

Incidentally my local Porsche independent suggested £3500-5000 to sort. My rusting manifold bolts were mentioned as an issue. Car runs sweetly otherwise.

[Triops]

Incidentally my local Porsche independent suggested £3500-5000 to sort. My rusting manifold bolts were mentioned as an issue. Car runs sweetly otherwise.

[Triops]

To be fair reflecting on this I think it involved other sensible replacements while the covers were off. Truth is that at certainly £5k it would be an uneconomic repair. I was gutted to hear that sort of price quoted. £1500 I can see if engine dropped as well. Dunno …

[the baron]

8 hours ago, Triops said:

Incidentally my local Porsche independent suggested £3500-5000 to sort. My rusting manifold bolts were mentioned as an issue. Car runs sweetly otherwise.

That’s engine rebuild territory, there another things to investigate first before you write the car off

[Triops]

Shan’t do that it’s pretty quick even with this issue. I paid 5k it came with new tyres and a hardtop roof. Red leather interior, decent service history.  Classic silver look. It’s still a great sports car. It was a little uneven on tickover when hot but I reckoned it was the maf which had been cleaned a few times before, also the coil packs were split. I had it checked by a Porsche independent before I bought. Nothing critical was identified.

[Kay Pee]

I recently changed my (2.5) bank 1 variocam with the engine in-situ, albeit on a car lift. My problem sounded similar, and I had P1341, P0300 and other misfire codes.

I had cleaned out the TB, checked for air leaks around the inlet manifold and checked plugs and coils but to no avail. A specialist checked the cam timing using Durametric and confirmed a cam timing deviation of about 13 degrees on bank 1. The signs weren't good.

After taking the bank1 cam cover and both cams out using the 101projects guide, I discovered it was just the solenoid (electrical actuator part of the variocam) that had gone, that was verified (before disassembly) by checking the resistance of the terminals on the 2 pin plug tail of the solenoid. Bank 2 was correct at 13 ohms.

[Kay Pee]

In addition, I noticed that bank 2 was a lot harder to access than bank 1, and may required dropping the engine or removing other stuff to be able to remove the cam cover and variocam.

My engine is an early 2.5 with 3 chains and the most basic variocam type (on/off), which may vary slightly to yours @Triops

[Kay Pee]

Just dumping the info here before I forget it and in case it's of use to fellow BoXa'ers 🙂

My 2.5 variocams seemed to operate below 1500rpm which meant that only idle and starting off was affected. Stalled quite frequently on the reverse into our driveway 🙈

I ended up also replacing the o2 sensor on bank 1 as the heater circuit failed on it too. This is the primary o2 sensor before the cat.

[Kay Pee]

On 4/2/2022 at 10:00 AM, Triops said:

Shan’t do that it’s pretty quick even with this issue. I paid 5k it came with new tyres and a hardtop roof. Red leather interior, decent service history.  Classic silver look. It’s still a great sports car. It was a little uneven on tickover when hot but I reckoned it was the maf which had been cleaned a few times before, also the coil packs were split. I had it checked by a Porsche independent before I bought. Nothing critical was identified.

It's sooooooo worth fixing 😄