My engine won't spin over 5krpm

[jon grindall]

Just picked up a 2005 987 Boxster S and noticed what appears to be rev limiter kicking in at between 4-5k rpm. Below that the engine is smooth and responsive. MAF? Fuel pump? any ideas?

Jon

[logray]

Is yours a Tip?

Have you read out the fault codes?

Have you ohmed out the crank position sensor? (search)

[jon grindall]

No - manual

Not yet checked for fault codes etc (only had the car a few hours)

Just wondered if these were recognised symptoms of something simple and cheap to fix!

[logray]

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.

[jon grindall]

Cheers for that. I'll try my local indy tomorrow and get a scan done

Jon

[jon grindall]

Inconclusive visit to Indy. No fault codes present. Strangely, the car revs freely when stationary. Going back in next week for further investigation!

[JFP in PA]

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...............

[jon grindall]

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.

[JFP in PA]

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 March 7, 2012 by JFP in PA

[logray]

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 March 8, 2012 by logray

[JFP in PA]

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 March 8, 2012 by JFP in PA

[logray]

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!

[JFP in PA]

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.

[Nick_USA]

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.

[logray]

I thought it was more like...

Engine not running 3.8.

Engine running 3.3 (indicating functional FPR)

[Nick_USA]

I thought it was more like...

Engine not running 3.8.

Engine running 3.3 (indicating functional FPR)

Just revisited the workshop manual says 3.8 for both static and idle.

[logray]

Interesting, well the 3.3 bar at idle is for a 996 with a FPR.

[JFP in PA]

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...............

[jon grindall]

OK Now I have fault codes. "Check Engine" message, and codes P2187 & P2189 (with grateful thanks to Nick_USA)

[JFP in PA]

I'd wager that the codes are for RKAT values would indicate an overly lean O2 codes for banks 1 & 2 at idle.

Edited March 11, 2012 by JFP in PA

[Loren]

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)

[jon grindall]

Thanks Loren (and all). I'll let you know what the workshop finds. This is a great start.

Jon

[Nick_USA]

I'd wager that the codes are for RKAT values would indicate an overly lean O2 codes for banks 1 & 2 at idle.

Codes values do indicate lean at idle.

[wvicary]

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.

[Nick_USA]

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.