Re: Loss of power

Boxster track car. 2002 with a :'99 3.4 996 engine. Engine randomly shuts down to idle while on the track. No response from the throttle. After shut off and restart, it's OK. No codes.

Any ideas?

Ed B

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Ed B
Boxster track car. 2002 with a :'99 3.4 996 engine. Engine randomly shuts down to idle while on the track. No response from the throttle. After shut off and restart, it's OK. No codes.

Any ideas?

Ed B

Does the engine manifest any signs of not having enough fuel like an irregular idle, backfiring through the intake?

Absent any signs of fueling problem I'm thinking the engine controller is seeing something it doesn't like and switches to limp mode.

If the engine is fitted with an E-Gas throttle body you might do an E-Gas calibration. Then the recommendation is to check for any E-Gas error codes afterwards. These might not trigger a CEL and you'll need something like a Durametric to retrieve the error codes.

An OBD2 code reader/data viewer/logger might be helpful in that you can log engine telemetry like coolant and intake air temps, MAF, TPS, ignition timing and see if there is a sudden change in the engine telemetry as the engine goes from ok to not ok and idle then what these values look like after engine off and restart.

Mark,
There is no sign of a fuel problem. Idle is smooth and no backfires or misfires that would indicate a fuel problem. I agree that the ECU sees something it doesn't like and switches to limp mode. There is no sudden loss of electrical power. It does have E-gas throttle body.
We did look at some parameters with my PST-2, and all looked good, but this was after a restart. It's hard to limp off a track in limp mode at a DE event. Officials and flaggers get upset at delaying the event.
Weather was sunny, about 50 degrees, with a cold northwest wind.
We suspect the E-gas throttle control or maybe a connector, but without PST-2 and limp mode we are just guessing. We may have to throw parts at it and what happens.

Thanks,

Ed B

Based on my experience I can tell you an engine off followed even if followed immediately by an engine start can cure, at least temporarily, a lot of ills. My Boxster manifested symptoms of what proved to be a bad VarioCam solenoid/actuator and yet an engine off followed by a restart had the symptoms gone. They remained gone during the 30 mile drive home.

At other times O2 sensor errors would appear but I learned that an engine off/on cycle had those sensors acting like brand new sensors. Only when I had the OBD2 code reader/data viewer connected and became more familiar at about when the sensors would act up was I able to catch them in the act. ('course, I could have just replaced them as the error codes were pointing to them as being bad, but I wanted to see what "bad" actually meant.)

Since you have access to a PST2 I think you need to look into as I suggested an E-Gas calibration then using the PST2 to query for any errors, unless of course you have already done this then nevermind. My advice is based on what I came upon in the factory manual the section on OBD2 diagnostics.

If the PST2 has any E-Gas tests you can invoke that's probably a good idea, too.

You didn't say -- at least I don't recall you saying -- if the car is a manual or Tip. If a Tip you might see if the Tip controller has any error codes. The Tip controller can I believe signal the engine controller to enter limp mode.

I also read -- I have *not* had any way to test/confirm this -- but if the engine controller detects too high engine coolant temperature (or I seem to recall reading intake air temperature, too) it can enter limp mode.

Ed
Have you had this car/engine setup running for some amount of time without issues or is it new to you?
Had a buddy with a 2003 Boxster that put in a 2000 3.4L 996 motor that eventually worked out ok, but had issues after the initial installation. IIRC, both cars had Egas from the factory.
Didn't all the '99' porsche motors all have throttle cables or did the '99' 996 models get the Egas first?

Ed & Marc,
The boxster in question is mine and has been working as it should with the current engine & ECU for 2 years. A very experienced wrench suggested it could be the throttle body as he has seen a number of these e-gas throttle bodies fail on a number of different marques. I don't know if this is a classic "limp mode" or not but it feels like an old style cable has broken and the engine just goes to idle until I shut it off and re start which obviously re boots the ECU.

Also, if I replace the throttle body will I have to do an e-gas configuration and what is that procedure?

Thanks, Dennis

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Dmaz
Ed & Marc,
The boxster in question is mine and has been working as it should with the current engine & ECU for 2 years. A very experienced wrench suggested it could be the throttle body as he has seen a number of these e-gas throttle bodies fail on a number of different marques. I don't know if this is a classic "limp mode" or not but it feels like an old style cable has broken and the engine just goes to idle until I shut it off and re start which obviously re boots the ECU.

Also, if I replace the throttle body will I have to do an e-gas configuration and what is that procedure?

Thanks, Dennis

Almost certainly if something in the E-Gas system (pedal, TB, etc.) is replaced a calibration should be done. (I do not know of something else needs to be done -- something like "introducing" the new hardware/controller to the car -- which could require a suitable diagnostic computer (PST2, possibly Durametric).)

Since the engine and throttle body are from a 996 and the E-Gas pedal and related hardware are Boxster I'm not sure but I don't believe this makes any difference, I believe that both vehicles have the same E-Gas calibration procedure.

From my Boxster days... With no pressure on the gas pedal throughout the procedure and with the key off turn the key to the on (1st) position. Leave the key in this position for at least 60 seconds. Turn the key off and leave off for at least 10 seconds. The next time the engine is started the calibration is complete.

What type of engine and tranny mounts are you using?
I have seen knock sensors confused with engine vibrations from solid or semi-solid mounts which cut back power thinking that the engine is knocking.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Mounts are wevo semi solid mounts. I have had these on the car for 4+ years with no problems

You may have had them in the car for 4 years, but the knock sensors can start to deteriorate and get confused.
You may have faulty knock sensor wiring or connectors which make the ECU assume the same thing.
Is the 3.4 liter transplant you put in an e-gas engine, or is the throttle body cable-operated?
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

E-gas throttle body & pedal. Will it run if the knock sensors are disconected?

Yes, and NHMS is a very bumpy track. I may try removing the knock sensors from the engine and isolating them. Problem is since I can't run the car on the street I will have to wait for next track event to try that.

Grant

gee-lenahan-at-gee-mail-dot-com

problems are the worst. You have no stored or pending codes at all?

This could be as "simple" ( and maddening) as a bad connection, wire, sensor. or even poor power or ground to ECU or any of those sensors....

Yuk. track cars have lots of vibrations. Lots of chances to loosen stuff, or rattle stuff and damage it.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Checked with PST2 and no codes stored. Wife had double hip replacement Friday so I'm spending a lot of time the hospital. I did order a new throttle body and will check more wiring (ohm out pedal wires, clean grounds etc.) and report back.