earossi

JB,

Thanks for your comment regarding the ECU. It seems to be "just" my opinion that the ECU is suspect. The folks who work on these cars have essentially concluded the the ECU is not suspect given the testing that was done by the Bosch ECU repair facility that tested the unit. Their conclusion was that the issues being experienced are external to the ECU. Since the testing of ECU's is something I know absolutely nothing about, I have to trust their judgement. Having said that, since we have proved out essentially all the sensors that provide input to the ECU, I keep thinking that the ECU has to have some involvement in the issues.

And, the only absolute way to eliminate the ECU as the culprit is to substitute another ECU. Quite simply......."extra" ECU's for a 1998 993 seem to be non-existent. I have checked with several repair facilities, and they all say that finding a spare ECU is a problem. I could purchase a new one, out of Germany, for a little over $2000, but would then have to pay another $1000 to configure it for my car. That makes it a fairly prohibitive experiment. If I "knew" that the issue was the ECU, I would gladly pony up the funds to buy a new unit. But, $3000 to "test" whether the ECU is the culprit is to much at this stage.

By the way, I like your wheels.....I have the same model rims on my 993.

techman1

Also wondering how a vacuum leak would show up, I recall:

The cold startup, the exhaust readings are pretty close. After a specific time, the readings get whacked, different side to side.

Proposal, could the SAI be covering up a vacuum leak, and could the readings after it turns off point us to the correct side?

Mr Swed

As noted before, the ECU got a clean bill of health from ECU Doctors in Florida. But, the ECU is one of the items that underwent modifications during my rebuild. The ECU was sent off to have it modified to adjust for the slightly more aggressive cams installed. And, at the same time, I had them deactivate the immobilizer function. Deactivation of the immobilizer removed a huge PITA issue for me. The interlocks on starting the car were always a huge annoyance to me. As now configured, the car starts without having to activate the system with the key FOB. And, I no longer need to depress the clutch pedal before I can do a permissive start.

So, keep the ideas coming. And, thanks for the support.[/QUOTE]

Hi,
Are you sure that Ecu Doctors in Florida have checked that the modified software (for the more aggressive cams) is working as intended? Do they have that knowledge or are they focus on the hardware? Have you talked with the company that modified the software about the issue? (you did modify the software as I understood)
I would try to run the car to the point where the problems start to accrue and then logg actual values like ignition angle, temp, idle switch, etc to see if I could figure it out from there.
Just my thoughts
Regards Rob

earossi

In my last conversation with the shop, I was informed that the CO readings had evened out, so that both sides of the motor are now running at 1% or lower CO readings with the SAI pump shut down. Not sure what changed, but the CO's are now reported as normal.

earossi

I talked to the shop yesterday. They had drained the fuel tank and put in fresh fuel. The car appears to start and run fine. They suggested that I pick the car up and put some miles on it so that the engine can go through an adaptation and to see if the stalling issue is still evident or if its characteristics have changed. I will get the car tomorrow and we'll see.

The one symptom that is still evident is that the car continues to have a lumpy rough idle once warmed up. It's been a long time and I'm not certain that I can comment on this except to say that the idle on my 993 has always been a little bit rough. Certainly not as smooth as the 3.2 I had in my 89 Carrera. I had just assumed that it was characteristic of the model. Add to that the fact that I have added RS cams, and idle is less smooth than before doing the cam install.

So, I'll keep my fingers crossed and see what the car does after picking it up. The last time I did this, I experienced my first stall within a mile from the shop.

I'll report back my impressions. Sure wish that we had found a definitive issue.

Thanks to all for hanging with me this far. It's been a journey.

Bill Verburg

when the car was smoked did that observe the vacuum solenoid up under the dash for the heater? It's easy to forget about.

RS cams will cause the idle to deteriorate a bit but not much, more on a 3.6 than a 3.8 and the idle is usually raised a bit to mask it.


Sounds like it may be a software issue

earossi

Hi Bill,

I doubt that anyone looked for a solenoid under the dashboard. Is that something that is on all 993's or just the 1995 model? And, what is the purpose of the solenoid? I'll discuss with the shop, but no one has mentioned this solenoid until you brought it up.

Thanks.

Bill Verburg

It's on all of them, it controls the heater flaps, I doubt that a leak there would cause the symptoms you described, I had a leak there but it just let the vacuum reservoir bleed down a little faster. There are 2 oe check valves to prevent that but for some reason neither works on that part of the circuit, I added a third check valve just for that circuit.

The 2 other check valves work on
1) idle and tank vent circuit and 2) the brake circuit

there are 4 other solenoids that have connections prone to leakage and none have a check valve oe
1) on the engine compartment fresh air vent(this is removed for an RS type heat setup)
2) resonator flap
3) vram actuation(both are actuated by 1 solenoid w/ a y connection)
4) anti run on valve

nine9six

Ernie,
Saw your WTB post for a 98 ECM...

I am not sure, but a call to your pal Steve W. will confirm if you can use a 97 or 98 ECM.

earossi

I did talk to Steve about ECU's several months ago. First off, the ECU's are year specific. I need the ECU, with its unique part number for a 1998. Steve used to have a "spare" but loaned it to someone and it never made its way back to him.

I have located the correct ECU at ECU Doctors in Florida. They have one that they can do an exchange for me. They would move my software to their box and do an exchange. Pretty pricey, but less expensive than getting a new ECU from Porsche ($2200....and the last 6 units are in Germany!)

If I knew that my ECU was bad, I would come up with the money to buy the one at ECU Doctors. But, not knowing if it would solve my problem, its a pretty expensive "gamble".

So, I will pick up my car tomorrow and then just start driving it. If the stalling resumes, I'll have to think about my next steps. But, as my tech said....hey, we have done a lot of things to the car......we suggest driving it enough miles to allow for a full adaptation to see what the ECU "learns" about itself. Having not driven the car for 5 months.....I'm going to have to go through a re-learning process!

vincer77

Would they let you borrow or rent theirs. I wouldn't think you would want the programming transferred in case the problem is in the programming.

earossi

Thanks for your response Vince.

Interesting point about the issue being in the software mods and not in the ECU hardware. Someone earlier on made a similar comment. It's a question I will pose to the guys at ECU Doctors. I guess they could provide their ECU without my programming, though they would have to defeat the immobilizer circuit in order for my car to use it.

Incidentally, for any following this thread, I did have the immobilizer deactivated in my ECU. Best money I have ever spent on this car! That feature of the car was a daily annoyance for me every time I drove the car. It is so nice to NOT have to push the key fob button several times to allow me to start the car and to NOT have to push in the clutch pedal to overcome the starter interlock. My Porsche is the last place I want to be reminded of big government dictating how to start my car! Sorry for the rant. But, having the immobilizer deactivated is about $500 from ECU Doctors. In addition to that, you will have to replace the starter relay with a jumper relay for about another $50, and you then have immobilizer freedom!

Then your key FOB is only used to operate the power door locks, or used mechanically to open a door lock (if the fob battery fails), and to start the car. Total bliss!

nine9six

Actually I was thinking you wanted to try a 98 unmodified ECU/ECM (potatoe/potaughtoe), in case it was a software or hardware glitch/issue.

Did the car ever run correctly after having the ECU Doctors flash the module?

If so, I would tend to not suspect the software; but ECU's are static sensitive devices and it is possible you have a static discharge damaged chip somewhere in your ECU, and it is manifesting itself as a intermittent defect as things warm up.
Anyone in the aerospace, aircraft, communications industry can tell you these are real issues.

p.s. I have yet to witness any automotive shop personnel, ground themselves and/or wear a ground strap when working on static sensitive devices such as an ECU. ...Or even use proper soldering irons and soldering workstations when handling such equipment...

Jus thinking out loud, while trying to be of some help...

You have checked so many possibilities, it now seems prudent to look closer at trying a different ECU.

Lorenfb

"As noted before, the ECU got a clean bill of health from ECU Doctors in Florida. But, the ECU is one of the items that underwent modifications during my rebuild. The ECU was sent off to have it modified to adjust for the slightly more aggressive cams installed. And, at the same time, I had them deactivate the immobilizer function. Deactivation of the immobilizer removed a huge PITA issue for me. The interlocks on starting the car were always a huge annoyance to me. As now configured, the car starts without having to activate the system with the key FOB. And, I no longer need to depress the clutch pedal before I can do a permissive start."

First BIG mistake!

"I did talk to Steve about ECU's several months ago. First off, the ECU's are year specific. I need the ECU, with its unique part number for a 1998. Steve used to have a "spare" but loaned it to someone and it never made its way back to him."

Not totally correct! All 993 DME ECMs will run the 993 engine without any running issues, i.e. with the exception
of the '95 which is a totally different DME ECM. The problem occurs when the '98 DME ECM is used in the '96 car,
i.e. emissions faults will occur.

"Actually I was thinking you wanted to try a 98 unmodified ECU/ECM (potatoe/potaughtoe), in case it was a software or hardware glitch/issue."

That needs to be resolved, i.e. who really knows what was done to the DME ECM?

"Did the car ever run correctly after having the ECU Doctors flash the module?"

And did the original DME ECM come back?

Read this Pelican thread:
http://forums.pelicanparts.com/porsc...cu-repair.html

earossi

Please do not apologize for thinking out loud. Your thoughts and those of others are what have kept me energized in this issue.

Let's clear up a little disinformation first. My ECU was reflashed by a third party firm on the West coast of the country, as far as I know. Since I am in the East, I chose to send the ECU to ECU Doctors for two reasons. First, they were a "disinterested third party". My expectation was that they would be unbiased in their evaluation of the ECU which had been re-flashed by someone other than ECU Doctors. Second, my tech has used ECU Doctors in the past and has confidence in their competence and service.

Initially, I sent my ECU to Steve Weiner who has someone on the west coast that does his ECU work. I do not know who that is. Steve does these types of modifications as his business, and does terrific work. So, it was only after checking all other areas of potential issue that I turned back to having the ECU evaluated.

To answer your most pertinent question about whether the reflashed ECU ever worked correctly the answer is NO. From the first start until today, the stalling issue appeared immediately after completing the engine rebuild, which included the reflash of the ECU. So, the ECU has got to be suspect.

That is why it was pulled and sent to ECU Doctors for testing several months ago. Their feedback was that the ECU tested out properly. Since ECU testing is a "black box" art form as far as I am concerned, I do not even know what is involved in their test procedure. Do they test just the hardware.....or can they evaluate the software? I honestly don't know. They did suggest trying other software, but we did not follow up on that suggestion since they did not say that the software was at fault (sounds confusing).

So, to have Loren materialize on this thread is welcomed, although his opening remark about my "Big Mistake" is confusing and unfortunate. Was the mistake that I sent the ECU to ECU Doctors? Was it that I had the ECU house defeat the immobilizer? Or, was it that I did anything with the ECU? I guess that I will have to wait for Loren to clarify his comments. I truly welcome the assistance of anyone that has knowledge of ECU's and how to get mine correctly evaluated.

So, I am now pursuing having the ECU re-evaluated. I called ECU Doctors yesterday and had an encouraging discussion with them. They have, in stock, a used ECU for the 1998 993. And, they are willing to "loan" the ECU to me for evaluation. I did not work out the details of the swap, other than to determine that they have the correct hardware, and that they are willing to work with me to determine if my ECU (or its software) is at fault. In the end, if their ECU corrects my problem, I can purchase their ECU. If my ECU proves to not be the issue, then I assume I would be liable for a usage fee, which is fair.

Hopefully that addresses your questions. Your "thinking out loud" lends support to moving forward with the ECU evaluation......so thank you for sharing your thoughts.

And, Loren, if you read this, I would truly welcome your thoughts, if they can be delivered in a constructive and less abusive fashion. I have read a number of threads in which you have participated. So, I respect you for your technical ability. But, I struggle with your attacks which are not usually warranted. Hopefully, you will accept my constructive criticism for just that. You are a valued resource. I just need to know how to properly engage you. Please PM me if you wish.