Awgm95

Hi guys,

I’m new to porsche ownership as I have just purchased a 2005 Carrera S.

Although it has a slight hesitation between 4500-5000rpm and after that just doesn’t seem like it’s pulling like it should.

first thing I did was coil packs as it had those symptoms but made no change.

after disconnecting the MAF to test all the power at the top end was restored and pulls like a train - so I assumed maf was to blame - although with a new one fitted the problem is actually worse.

the next thoughts I had were either fuel pump or throttle body, although I’m starting to rule out fuel pump as it had all the power back when it he maf was disconnected.

has anyone seen an issue like this?

also no codes at all on the scan tool - and that was a proper scan tool rather than the eBay special

thanks

voiceprint1

take a look at this article, it may lend some insight into what the MAF is or is not doing, but my guess is that the wiring has become bad, or at least not properly feeding input to the ecu on air flow, the throttle body could also be pretty worn at over 17 years old. If your seeing massive changes in fuel consumption that is another tell there is a problem.

https://effective-tuning.com/blog/ma...elete-removal/

CarreraAlex

shot in the dark if it hasn't been explored but is it a 6MT?

could be a clutch slipping or something in the trans? although that's a little high in the RPM. when my ducati clutch went it was in the higher power band but only with WOT i noticed it.

gcthree

My '02 996 Carrera had similar symptoms. I tried, literally, everything to diagnose the problem. One shop spent a day with the car and could not find the issue and did not charge me because they didn't cure the problem. (I'll always recommend them!). Turns out that our local Porsche technician at the dealership figured it out. There is a resonance chamber inside the air box and it had split in 2 pieces and been glued back together...only to come apart and create running issues that could not be found. Might be something as dumb as that...

Petza914

Check your cam values. If the variocam solenoids aren't working or the cam position sensors, the engine may be sensing knock and going into protection mode. If you accelerate really slowly through the rpm range, you should hear the exhaust note change around 3,800-4,000 rpm as the variocam kicks in - does it?

voiceprint1

That is interesting about the cracked airbox, and might explain why it's happening at that rev range, since the engine is drawing in max air at that point. on the 997.2 the airbox takes a bit of time to get off, but it's basically 1 torx screw type, and a second smaller torx to remove the filter so you can inspect. I believe that resonance thing is on the bottom of the assembly, but don't quote me on that, should be similar on the 997.1

HartyWags

Not an expert but when I was looking for my car I test drove a 2009 that had similar "hesitation" or shuddering when accelerating. It turned out to be the high pressure fuel pump was failing. I believe the 997.1 has 2 pumps, the first low pressure to pump the fuel from the front to the engine, and the high pressure for injections. I would check that.

Awgm95

Hi guys,

so I replaced the throttle body and it got rid of the hesitation between 4500-5000 but still hasn’t got the top end power.

plus it’s failed an emissions test on high co2 - so running rich

it he got ab aftermarket exhaust and the previous owner thinks it has an ecu map as it does seem to pop and bang from the exhaust - could these all be linked?

Petza914

The tune and your failed emissions test could absolutely be linked. You should test fuel trims while driving the car and see if it's rich all the time or only above a certain rpm. If it happens around 3:800-4,000.rpm and above, could also be linked to the variocam system.

voiceprint1

I would look at finding a decent indy before throwing more money in parts at this, as it seems like a fuel delivery issue that might be hard to sleuth out.

CaptainPcard

Did you figure this out? I had a similar issue. Turned out that rodents had chewed the wires to both knock sensors. Codes P0327 and P0332.

cwheeler

This is incorrect.
997.1 have the "old" port injected engine with a standard fuel pump until 2008. 2009 engines changed to dfi and required the HPFP added in to the system.