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997.1 turbo boost issues.

Legzr1

Well-known member
Joined
15 Feb 2017
Messages
78
Had the car a couple of weeks now and I'm working my way through various niggles (my last post was regarding the key refusing to do anything but that seems to have sorted itself out).

So, next in the queue...

I had an occasional engine light linked to O2 censors after the previous owner fitted 200 cell cats and a sports exhaust (manufacturer unknown - I really should find out!) - I had this booked into my local Indy to sort on the day I bought the car but had to wait as they're rather busy. I used the car for a week, getting used to it but a weird issue raised its head - when first started and within a few minutes everything is fine, boosts normally etc. After getting the car to temp and giving it some real throttle it's seems to boost up to around 0.4 bar then won't build any higher - at around 3000rpm when it's usually starting to really fly the engine seems strangled and really struggles to rev over 5000rpm.

If the car is stopped and the key removed for a minute or so it's perfectly fine on re-start. Eager to rev, boost up past 0.6 bar and the occasional overboost arrow on the dial when in sport mode. Just what a Turbo should be like.....and then it drops into what feels like a limp mode again, refusing to boost over 0.4 bar :sad:

Now, the cars been into the Indy, new tyres and 02 censors, faults checked and cleared and ready to go.
It was great.

For 5 minutes then the boost fault reappeared.

It's been back to the Indy again - they've been great, fitting me in even though they're very busy and the cars been on numerous test drives. It's had a good going over and they discovered an issue with one of the turbo actuators - it was stripped, greased and tested and everything worked great.

Until today, car warmed up, throttle to the floor entering a dual carriageway in second gear and it's happened again :x :x :x

I'm about to ring them and get it in again but there are no fault codes, no engine lights and I'm not really sure what else they could check.

Any ideas folks?

Last time I spoke to the mechanic we covered many possibilities and boost leaks were mentioned with a smoke test but I'm not sure if it was actually carried out or was left as the car felt fine after work to the actuators.

Thanks for any help or pointers.
 
I'm going to assume the turbos and actuators are fine .. Your garage has already looked ..

i'll go for something a bit different .. Fuel pump not delivering full pressure .. maybe a slight blockage on the filter .. let's say a bit of paper for argument's sake ..

Running and it gets sucked against the intake filter of the pump and restricts fuel flow .. switch off .. no sucking action and it drops away so is fine for a bit until its run again .

I'm not saying this is the problem .. i'm just thinking perhaps its an unrelated fault to the turbos ..

Either way i would advise the fuel pump / pressure being checked .


From memory you can activate the actuators with a tester .. and with ignition on they run a cycle to check endpoints so you can see the correct operation .

Some things i tend to read up on before fault finding as i don't know everything .. same as all of us .

EDIT

One other thing i thought of .. maf sensors .. i believe you should get approx 1.23 volts at idle .. worth checking to see if they are around that value .
 
Thanks for the replies :thumb:

Car ran fine this morning after letting it warm up - full boost through a couple of gears but it did have a weird stuttering feeling at one point. At the point where it was just starting to make boost, down hill with barely any throttle there was a barely detectable stutter and the boost gauge (bar graph) displayed the tiniest amount of boost then off then on again really quickly. It was fine with a little more throttle and fine for the next 5 miles or so until I arrived at work. Maybe I'd caught it just at the point where boost was being made and it wasn't sure what to do??

Later today on the journey home, same issue as previous posts although I got far closer to home before lack of boost over 0.4 bar reared it's head again which is a positive I suppose...

Anyway, I've got the use of another car so I'll try and get it dropped off in a day or so and just leave it until it's sorted.

I'll mention the ideas above re: proper boost leak, fuel pump etc.

The fuel pump in particular might be worth checking out - some years ago I was chasing a fault on a 996.2 C2 and the way it struggled to rev out in any gear higher than second feels very similar to the 997T when in fault mode - fine up to around 3000rpm then terrible above that. A new fuel pump cured the 996 :?:

I'll update the thread once it's cured :thumb:
 
It's very easy to work out if it's fuel or boost control by data logging.
 
(Extremey) belated update...

Lots of things got in the way trying to get this sorted - small issues, large issues, fried ECUs and world pandemics.

But, *drum roll*, all done now.

For various reasons, mainly down to my lack of time, the car hadn't been properly boost/pressure tested. Smoke test revealed nothing nor did many visual checks of pipes, joints and connections.

Then, a proper pressure test.

0.2 bar and massive leaks on both inter coolers. Well, that would explain why it wasn't building and maintaining boost!
Coolers removed and in a very sorry state - 2006 car with getting on for 100,000 miles so no great surprise really.

The options were there to go big with possible future tuning in mind but I'm not really interested in high speeds and big bhp numbers so original spec Behr were sourced and fitted. The car has a Kline exhaust, 200 cel cats, BMC filter and was easily quick enough for me on the odd occasions I was getting full boost.

That was three days ago. These past three days I've finally got the car I thought I'd bought.

All serviced with the big 12 year stuff done, all fluids including tip box etc. Geo done and PS4S tyres. DSC pasm box installed.

And.....what a car! Quick, fast, almost shockingly so and handling so,so much better.

Exiting 2nd and 3rd gear bends, on boost with the DSC doing its thing keeping the car flat is magical. Seriously impressed.

Huge thanks to D&G Porsche yet again.


I'm off out to play with mates on their super bikes on bumpy B roads. :D
 
Spanish Proverbs

It is never late if the joy is good
 
is there any worse feeling n the world to have a turbo car and lose the boost.....

So glad u sorted it out
 
ehcsrop said:
Legzr1 said:
Then, a proper pressure test.
:D
Glad your car has been sorted.
What is involved in this test?

Using a compressor to pressurise the system to 25psi and see if it holds pressure correctly. The only real way for finding boost leaks
 

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