Jump to content

The RennTech.org community is Member supported!  Please consider an ANNUAL donation to help keep this site operating.
Click here to Donate

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

Recommended Posts

    You can remove these ads by becoming a Contributing Member.

Could be a throttle body/throttle sensor. Maybe crank position sender.

It would probably be good to check for codes and using a multimeter before the above swapping parts.

A lot of places such as autozone, etc. will scan codes for free.

Link to post
Share on other sites
  • Moderators

Suggest looking at the fuel system; M96/97's that have fuel delivery volume or pump pressure issues act this way, but only under load. You could just simply be running out of fuel at higher revs...............

Link to post
Share on other sites

That would be a wierd coincidence, as my GT3 (996) let me down with a duff fuel pump when I first got it. Symptoms were slightly different as it was fine throughout the rev range at first, then just refused to deliver under any load. However, that threw up a fault code straight away.

Link to post
Share on other sites
  • Moderators

Typically, the code thrown when the pump cannot supply enough fuel is for an overly lean condition (O2 sensors) or a general misfire (P0300-0306). I would suggest scanning the DME and see if any "pending" codes of that nature show (sometimes the pump is just bad enough to only lean out at very high RPM's, but then the fuel trims drop back in range when you take your foot out of the engine, leaving only the pending codes rather than active ones because the condition did not persist long enough). It would also be very easy to attach a pressure test gauge to the test port on the fuel rail and check both the pressure and delivery rates, only takes about 15 min. shop time.

Edited by JFP in PA
Link to post
Share on other sites

Just curious JFP if you normally measure fuel pressure at the rail at times other than engine off or idle. For example, do you expect certain values at no load 3000rpm, 5000rpm, etc.?

Edited by logray
Link to post
Share on other sites
  • Moderators

Depends upon what we are looking at; sometimes the fuel pressure and delivery is so low at an idle, trying to run it at higher revs becomes a moot point. Other times the idle pressure looks good, but bringing up the RPM’s (free revs) shows a sudden fall off, indicative of a fuel pump or regulator issue. That said, other times we have rigged up cars to take on a road test with the fuel pressure gauge taped to a window for observation purposes while pushing the car to look for a sudden drop off in pressure. We once had an early Boxster come back with a poor performance complaint shortly after a major service; turns out the new fuel filter was bad (internal obstruction caused by loose components) that only showed up with the jury-rigged pressure test setup and a “run it hard” road test. At idle or free revs, it looked fine. We have seen similar things when the fuel pressure regulator gets intermittently problematic. Sometimes you just have resort to “man invents tool” to figure out what to try next………..

I really can’t wait to have to do this kind of testing on one of the newer DFI cars running big time fuel pressure; the test rig line will have to be braided stainless to deal with the pressures (120 bar or about 1,740 PSIG) involved instead of the 35-60 PSIG of the early cars………..

Edited by JFP in PA
  • Upvote 1
Link to post
Share on other sites

120bar??? Smells like trouble to me if you don't have a monitoring system rigged up the right way. I hate messing around fuel, and at those kind of pressures you are looking at a pinto disaster waiting to happen.

Thanks for the visualizations and the reply. I have a feeling I've read that before with the gauges taped to a window. Carefully stored in the grey matter, and thanks again!

Link to post
Share on other sites
  • Moderators

Keeping the temporary test rig outside the car is purely for safety and to reduce any potential for having to get the smell of gas out of a customer's car.

At 120Bar, a leak that would be a small drip on the 50-60 PSIG system turns into a torrent that can literally slice through flesh in a heartbeat; really not anything to be messing with, even if you ignore the fire potential. We are looking at obtaining an suitable electronic pressure transducer to temporarily mount on the engine that would eliminate the need for a line and gauge.

Link to post
Share on other sites

The test of fuel pressure is done either static ie engine not running with the fuel pump activated using the PIWIS or at idle (no need for PIWIS) either way for an 2005 Boxster S you should get 3.8 bar +/- 0.2 bar.

Link to post
Share on other sites
  • Moderators

The test of fuel pressure is done either static ie engine not running with the fuel pump activated using the PIWIS or at idle (no need for PIWIS) either way for an 2005 Boxster S you should get 3.8 bar +/- 0.2 bar.

Only problem is that this type of test will not find issues like the fuel filter problem described earlier, or a pressure regulator that is on its way out intermittently under load conditions. Granted, if the car cannot pass the static test, there is a problem; but some cars pass the manual test just fine, but then crap out under load, which requires testing it dynamically to spot it...............

Link to post
Share on other sites
  • Admin

P2187 Lambda control adaptation FRAU (lower load range)

P2189 Lambda control adaptation FRAU (lower load range)

below limit value possible fault causes

- Incorrect main filling signal from hot-film mass air flow meter

- Fuel pressure too high

- Injection valve faulty (dripping)

- Tank vent faulty (does not close completely)

above limit value possible fault causes

- Intake system leaking (secondary air)

- Incorrect main filling signal from hot-film mass air flow meter

- Leak in exhaust system

- Fuel pressure too low

- Fuel injector faulty (stuck)

- Fuel pump delivery too low

Lambda control adaptation RKAT (range near idle speed)

above limit value possible fault causes

- Oil filler cap leaking (secondary air)

- Intake system leaking (secondary air)

- Crankcase ventilation leaking (secondary air)

- Incorrect main filling signal from hot-film mass air flow meter

- Leak in exhaust system

- Tank vent faulty (does not close completely)

below limit value possible fault causes

- Fuel pressure too high

- Injection valve mechanically faulty (dripping)

- Tank vent faulty (does not close completely)

Link to post
Share on other sites

Besides fault tracing the codes, I would also recommend re-setting the throttle plate adaption.

Just another diagnostic note on fuel pumps, I've also measured voltage/amps over and above fuel pressure on a road test with problem vehicles with suspect fuel issues. A few were down to poor ground connections/wiring.

Link to post
Share on other sites

Besides fault tracing the codes, I would also recommend re-setting the throttle plate adaption.

The OP has done this, ie disconnect the battery, reconnect, ignition on but don't start for 30 seconds then start, but it wasn't successful.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.