Receiver

Engine continues to run rough with occasional misses. Not my imagination as my tech agrees. No CEL's though and my tech did a search and it 's clear.

I've now changed the plugs, the coil pacs and the MAF. I've also run two injector cleaning bottles through with 2 successive gas fill ups. I'm running the best gas I can find and it is still running rough. My tech's next plan is to check the DME software to ensure that it is proper for this geographic location versus the deep south where the car originated. Any other ideas? I'm getting a bit frustrated.

Kevin

Have you pressure tested the complete intake?

Next datalog the fuel/injector duty cycle.

Receiver

Thanks Kevin. We'll try that next.

Macster

Not sure I subscribe to that geo specific DME software thing. I've driven my 03 Turbo (based in Livermore CA) from home to as far south and east as Fredricksburg TX to as far north and west as Lakewood WA. I've driven in cold (19F in Flagstaff and points east) and heat (118F near Needles). On way downto and once in Fredricksburg ran into a super low that dumped record rain on parts of TX. Of course I drove through heavy rain and high humidity. Across deserts there is no humidity. Just heat and elevation changes. Elevation changes range from "around sea level" in Indio CA to a bit below in some CA central valley locales to nearly 8000 feet above sea level going across I-40 near Flagstaff.

In all these various conditions never once encountered any indication from the engine it need geo specific DME software.

(I'll leave it up to your imagination what various locales I've had my 02 Boxster, the one with over 234K miles. Hint: From the far north west to south TX, up thru WIS. and over the top of Mich. and down. Across I-90, I-80, I-70, I-40, I-20, I-10, and up and down too many I-XXs to remember. In all kinds of weather. Not once did the engine act up that was due to any atmosphere or climate sources.)

Now if your tech wants to verify the DME is stock and has a stock tune that's different.

I assume the misses don't result in a CEL nor any error codes? If this is the case, the misses might not be coming from the engine or its controller, fuel system, ignition system, but from the E-Gas accelerometer.

I've never done it but I read reports of several who have and that is they've removed the E-Gas floor pedal assembly and cleaned the mechanism and relubed it.

One guy who was experiencing something similar to what you report even went so far as to remove the throttle body and remove or at least expose the butterfly actuating mechanism, the gears. He cleaned these and regreased them and his car's miss-like hesitation symptom vanished.

My info is there are no owner or field serviceable parts in this assembly and my references only offer that the assembly be replaced if it is suspected (or confirmed) as the source of various symptoms.

However, this one guy was desparate and his report was after the cleaning all was well.

Since tearing into this is not covered by anything I have to refer to I can't recommend you do it.

If you have the ability to data log various engine sensor values and derived values, such as Kevin suggested, I would take that route. If you can see no data that suggests its source is the cause of the miss then perhaps the E-Gas pedal or throttle body butterfly actuator is worth considering?

Have you observed the boost gage during these miss sessions? Have you verified the intake system is clear of any trash or rags? All it takes is one rag in an intake manifold -- left there by accident or shoved there by someone who had an "in" for a co-worker and sought to sabotage a car the co-worker was working on -- to drive one crazy trying to figure out why the engine runs so peculiar.

Oh, there have been reports, I can't say I've ever come across one for the Turbo, but reports of people removing screens from their engine's intake with the mistaken notion of gaining some HP by increasing the air flow through the intake. Some of these are classified as "snow" screens, or debris screens, but they are not there to catch any debris. That is the engine air filter's job. The screen is there to have a positive effect of the air flow either just ahead of the MAF or just ahead of the throttle body and butter fly valve. If there is such a screen, supposed to be a screen in the Turbo's intake system -- I can't remember ever coming across one though -- you want to verify it is present and installed correctly.

Whatever you find out I'd be very interested in reading about it. Even if it turns out I'm wrong and there is something to this geo-sensitive DME software thing.

Sincerely,

Macster.

Receiver

Thanks Macster.

I'm taking Lucy in Friday and I'll show all of the responses to him and see what he thinks.

Kevin

I think that you will be spending diagnostic monies without getting it fixed.

You could have a fuel pump issue and not even know it.

You have to datalog the engine values to see what is going on..

Receiver

I hear you Kevin.

Given that I'm not a mechanic, I am not familiar with the terminology "datalog the engine values". Assuming my tech is good, will he understand this terminology or do I need to be more specific?

Your help is appreciated as always.

Macster

Well, if I may offer yet another comment on your situation, my belief is that if I have to suggest or tell my tech what steps to take to diagnose the source of a symptom with my car I have the wrong tech.

All you need be able to do is describe the symptom with as much pertinent detail as possible and be able to either demo the symptom or instruct the tech under what conditions the symptom appears.

What Kevin is referring to by data logging is to connect an appropriate OBD code reader/data viewer to the car's OBD port and query the car's engine controller for various sensor values like coolant temp, O2 sensor voltages, etc., and derived values like long term fuel trims, to name just a few and collecting these over a length of time. Probably over the span of time before the symptom appears, while the symptom is appearing, and perhaps after.

(As an aside there are generic OBD code readers/data viewers/loggers that allow just the obtaining of the basic OBD emissions related sensor and derived data values. But a well-equipped shop that works on Porsches, at least modern water cooled Turbos, should have at least a Durametric and I would prefer to see a PST2 (Porsche System Tester 2) or something even newer, something like PIWIS (I forget what this stands for). These types of sophisticated tools expose to the tech more esoteric but insightful nonetheless info. They can also have suggested diagnotics procedures to follow to guide the tech to the root cause of a symptom.)

The idea is to try to see from one or more sensors or derived values what's going on. Now which sensors or derived values to log?

That's where the tech's experience, training should come in. Granted he might start out looking at say short term fuel trims or O2 sensor values and if they look ok and after some more thought on the subject switch to data logging other values until he encounters values or readings that provide him with a clue as to what's going on.

For instance he might note the MAF air flow value dips or spikes concurrent with the symptom. Now this might be a bad MAF or maybe some mechanical glitch in the accelerator pedal or the operation of the butter fly valve in the throttle body.

You want a tech that starts out at least logging data that makes sense. If for instance he wants to measure tire inflation pressures you probably have the wrong tech, at least for your original complaint.

Sincerely,

Macster.

Receiver

Thanks for your help

Receiver

I picked up Lucy this morning. I have owned her for almost 3 months and she has not run properly in all that time. Today was a revelation. Power is awesome and very smooth. No more hesitation. No more having the computer try to compensate for an unknown problem.

Pressure tested the intake system and replaced a broken clamp behind the throttle body for diverter valves. Problem solved. My hat is off to Courtney at Autowerkes who found it.

theporscheguy

Hopefully the frustration that you have gone through will not outweigh the true magic that Lucy can provide in the future. Here's to many trouble free drives.