maybe you guys can help.... '05 C2 engine losing power.

the 997 forum has yet to yield any insight, but there is a good bit in common with the 996s, so I thought maybe some of you would have a few ideas. No check engine, no oil warning, no other indications. temps are fine. oil/water both. coolant is full, oil was half-quart low (since remedied) oil pressure gauge is "3" at idle, maxed under any load. car has run well and run strong for over 3000 miles in the last 2 weeks... this morning it just decided to be a 150hp car and not a 325hp car. engine is smooth and quiet, no odd noises, just has no suds. my assumption is that any engine-management failure will throw a CEL. the spark plugs are (I believe) original, but at 37K-miles, shouldn't cause a loss of power like this without a noticeable misfire, which is absent (and would also throw a CEL). no PSM lights, brake warning light... no nuthin'.... a quick google search indicates these symptoms are not indicative of an IMS failure. (good news there) exhaust doesn't smell like fuel, so its not "gas but no spark" driven 25miles since it became symptomatic, still no CEL, which a MAF or o2-sensor issue should trigger. Engine runs smooth and quiet. this would lead me to believe the culprit lies within one of the following: -Fuel Filter/pump not flowing. would need to check FP levels at the rail to be sure.... google has yet to confirm/deny the existence of a FP test port. pump can't be totally dead as there isn't a primary/secondary, it's just one. so filter blockage/failure seems more likley there. -TPS/electronic throttle malfunction. throttle not opening properly... one would think that a TPS failure would trigger an error code due to an incongruent input with the MAF signal, so that would make me thing the TB itself is to blame.... which seems easy to reach, but can't be cheap! I would welcome any other ideas...

Sounds like it could be a sticking or failing throttle body, first stop clean the throttle body.

thx... hard to think that would happen at 37K, but 9yrs is probably enough.

Clogged cat? Total guess on my part, no idea if it would throw a code or not. Does the exhaust pressure feel the same on both sides?

pressure felt even... and that's LOW miles for a clogged cat! and it SHOULD throw a CEL...

What scanner you used? Stick shift or auto? Are the brakes dragging?

none yet... this is just from observation, experience, and deduction. I'll check the TPS tomorrow with a scanner.

Stick shift or auto? Are the brakes dragging? If you use a generic OBDII scanner, can you note the short term and long term fuel trims and the MAF reading at idle fully warmed up and at 3k rpm? That should tell us how good the engine breaths and whether the DME needs to do huge adjustments. If using Durametric, can you note the RKAT and FRA values on both banks? May also want to check if the CEL bulb is blown.

6MT CEL light works. it is lit when ignition is on but not cranked yet. it's a generic scanner... I'll see what I can get pulled tomorrow night. thanks guys!!!! this is more help in 90mins than in 5hrs in the 997 forum!

This vehicle does not have a fuel filter.. Look at fuel trim values to see if the system is trig to mask a problem, like Ahsai stated.. The fuel trim tells the story. If that looks good you must assume a mechanical deficiency and then go into reactive mode, by starting to look four signs that things are going south.

Throttle pedal feel normal? No play, equal resistance through full travel etc...

yup, feels normal.

One thought is - sometimes the DME will register a code but not throw a CEL. Puts it like in a "pending" mode. So the idea to check it with something like Durametric would be a good idea. Doubtful a generic OBDII scanner will show "pending" codes, but then again it might. One other idea, I was having low power, idle problems, hesitation and some pretty good backfiring. The engine just seemed to be dragging...badly. No CEL's. I was leaning toward the fuel filter or bad injectors. Long story short - turned out to be a cracked oil filler tube. You could barely see the crack where the accordion section joined the filler tube. This is a common problem...too many heat cycles. Replaced with the upgraded newer oil filler pipe. What a difference it made. The engine power is completely there and it just sings. Check for vacuum leaks, clean your MAF (or replace) and TB, and check your oil filler pipe/cap....make sure it is okay.

I agree with Ashai too. When's the last time you got gas? Possible bad gas maybe? Your mileage does seem low for any mechanical issues but then again, this is a Porsche.

filled with fuel Sunday evening, burned half the tank already... refilled yesterday thinking that might be the culprit, but thus far no improvements. it's parked for the day, fired up the JK for the first time in over 2 weeks! I'll hit it with the scanner tonight.

A dura metric would be a great investment. You could log gas pedal and throttle body positions to make sure they are working. You could also check out fuel trim as mentioned. It does everything to take out the guesswork.

With such a dramatic horsepower loss (325 to ~150) I would expect some engine codes. Try using an OBD2 reader to get some horsepower readings out on the highway under load. At least we can quantify the loss of power and work from there. That said, my first guess is MAF (followed by bad gas and vacuum leak.)

If you had bad gas you would probably get misfire codes. Old school test would be to put a fuel pressure tester and test the fuel pump. With no CEL i find it difficult to be a throttle issue. blockage in the exhaust system/collapsed cat would also cause a dramatic loss in performance. We bought a 95 wrangler once and the cat failed shortly after we got it. Jeep would not go over 45mph no matter what you did. Vehicle would have a very muffled sound.

I know yours is not a Turbo, but this might be helpful: From: http://911uk.com/viewtopic.php?p=821176 "I'm hoping someone out there can help. Car had a major service carried out at the local OPC, I then changed the spark plugs/clutch accumulator and gearbox oil. All was well for a day or two (with a 3 hour drive in the middle). Car appeared to go into limp mode, no engine lights or obvious running symptoms just 0.1 bar of boost pressure. I disconnected the battery for 15mins and all was well for another couple of days. I ordered a PIWIS cable and the following errors have come up: P2135 Accelerator pedal Signal implausible P0121 Factory Fault Code 117 - Throttle value or accelerator pedal potentiometer Signal implausible Has anyone seen these codes before? any suggestions on where to start? " --------------------------------------------------------------------------------------------------------------------- The Google gives: "Porsche > OBD/DLC Diagnostic Trouble Error Code > P0121 Throttle/Pedal Position Sensor/Switch "A" Circuit Range/Performance What does this mean? OBD Code P0121refers to The Throttle position sensor is a potentiometer that measures the amount of throttle opening. As the throttle is opened, the reading (measured in volts) goes up. The powertrain control module (PCM) supplies a 5 Volt reference signal to the throttle position sensor (TPS) and usually a ground also. A general measurement is: at idle = .5 Volts; full throttle = 4.5 Volts. If the PCM detects that the throttle angle is greater or less than it should be for a specific RPM, it will set this code. Symptoms Possible symptoms of OBD code P0121 Symptoms of a P0121 trouble code could include: Malfunction Indicator Lamp (MIL) illumination (Check Engine Light or Service Engine Soon light) Intermittent stumble on acceleration or deceleration Blows black smoke on acceleration No start Causes Possible causes of OBD code P0121 A code P0121 may mean that one or more of the following has happened: TPS has intermittent open or short internally Harness is rubbing and causing an open or short in the wiring Bad connection at the TPS Bad PCM (less likely) Water or corrosion in connector or sensor Possible Solutions 1. If you have access to a scan tool, see what the idle and WOT (wide open throttle) readings are for the TPS. Check if they're close to the specifications mentioned above. If not, then replace the TPS and re-check. 2. Check for an intermittent open or short in the TPS signal. To do that, you can't use a scan tool. You'll need an oscilloscope. The reason is because scan tools take samplings of many different readings over just one or two data lines and can miss an intermittent drop out. Hook up your oscilloscope and watch the signal. It should sweep up and down smoothly with no drop outs or spikes. 3. If no problems were noticed, perform a wiggle test. Do this by wiggling the connector and harness while watching the pattern. Does it drop out? If so, replace TPS and re-check. 4. If you have no TPS signal, check for 5 Volt reference at the connector. If it's present, check the ground circuit for open or shorts. 5. Make sure the signal circuit isn't 12V. It should never have battery voltage. If it does, trace circuit for short to voltage and repair. 6. Look for any water in the connector and replace TPS as necessary. " This thread reads similar to yours: http://www.6speedonline.com/forums/9...n-sensors.html ... Looks like you may need a new TPS (Throttle Position Sensor) ... have you had any internal water leaks, or flooding etc that may have caused the area around your throttle pedal to become damp or wet recently?"

thx.... I'm trying to get the scanner over here right now.

Could be your maf. I lost major power on my 6 on track(felt like i lost 100 hp). Never triggered the cel as well. Once maf replaced power came back to normal. Mike

drove around for 2 miles. no fault codes in the ECU throttle readings in the "Torque" app are ~13% at idle and ~86% at WOT.... disconnected the battery and will go through the reset/relearn process here when I have another minute. -------------------------------------------- re-connected battery, went through re-learn. no improvement. hmmmmmmmmmmmmmmmmmmmmmmmmmmm..... I'll pull the MAF connector tomorrow and see if anything screwy is going on with that.

disconnect your MAF sensor and see what happens. This I believe makes the ECU use default values.

The word I get is when a 997 loses power like you describe and with no CEL the fuel pump is suspect #1.

that's our suspicion as well, but I haven't found a check-valve yet.