dr bob

Fig Newton's Fifth Law of Electrical Reciprocity suggests that any time you have an expensive spare part on hand, the primary in-service part will never fail. I had tons of faith in that law until this week. I've been working on a project in New Mexico for the last couple months, with the 928 sitting at home with the battery maintainer attached. A month ago I snuck home for a couple days of R&R and some local social events, and the car was slow to start. Cranked fine but it felt a lot like it was flooded. Car was slurping fuel at a very noticably increasing rate too. Hmmm. Figured fuel pressure was the problem, so attached the FP gauge for a test. FP is fine, and holds well beyond the WSM time requirements. Vacuum tests om FPR and dampers say all is fine. Battery is showing some signs of getting tired though, evidenced by the dash display reset message showing up once in a while. Before anything was settled, I was back in New Mexico for a few more weeks. Came home again a few days ago, and the car is still tough to start sometimes. Hold the pedal way down while cranking, and it would sputter to life OK after a bit. Replaced the battery, thinking that maybe it was just the low voltage during cranking. Not so.

Finally, still in denial because of Fig's Law, I decided to just bite the bullet and put in the rebuilt LH brain that's been here for several years now. Thirty minute swap, easy to do, what the heck... Of course, that immediately cured all the starting symptoms, plus the car runs significantly better once started. Gas mileage is very significantly improved, not a small benefit these days.

Moral-- Pay attention to Fig Newton when you diagnose, but consider that many of his laws were promulgated before the 928 was conceived. Don't want to say they can be wrong, but also don't want to lose the benefit of their guidance the rest of the time.


Thanks go to Rich Andrade and Elektronik Repair. Rich warned me to swap the new brain in as soon as I got it, so I wouldn't get stranded. I didn't get stranded anywhere fortunately, but still would have saved a few minutes of wondering when the car was tough to start. In those several years, the rebuilt brain has helped half a dozen or so 928 owners figure out quickly whether or not they had LH brain problems in their cars. Four out of six 'testees' did.

Rich, the failing brain will be on its way to you shortly. Do your magic to it, and I'll slide it back into the car. That will free up the one that's in service now for others who might need one.

Rich and Elektronic Repair have been and continue to be generous sponsors of the annual Sharktoberfest events here, as well as other 928OC-supported events around the country. Can't say too much about the support that he gives to the 928 community.

SeanR

Great reading Dr. Bob.

the flyin' scotsman

I've pondered this issue for quite sometime also...........rebuild the OEM, replace the OEM with a rebuilt or have a 'spare' on standby.

Now that the intake is refreshed no reason to replace the LH for absolute security.

Great reminder Dr B that they can fail a slow death.............

Tom. M

kinda of a silly question..but is there a way to test the LH outside the car to see if it is "going" bad. I know swapping into other cars to see if they run the same..but suppose there is an intermittant fault that doesn't manifest itself every time? Car runs fine for days..and then goes bad...but then goes good again. last time it goes bad, swap in a new brain and it works fine?... Does Rich run diagnostics on it to see what the output is..or is it just assumed it's bad and the hybrid chip is replaced...and then good to go?..

the flyin' scotsman

From what I understand from the LH rebuilders you need a complicated to test bed to run all the test parameters and given you'd have to send your unit to them they may as well upgrade and replace WTAI.

dr bob

My symptoms were somewhat intermittant, and that initially lead me away from failed brain as a possible cause. The car seemed to run OK once it started. None of the injector clicking that some others reported as a clue. The car would start fine most of the time, a few other times it seemed like it was flooded. My mental diagnosis went through MAF as a possible cause, the FP regulator and the dampers possibly leaking fuel back into the intake, stuff like that. I swapped in the new brain because it was the next logical step in the procedure, a procedure somewhat skewed by the fact that I had the spare here on the shelf waiting.

Meanwhile, since I bought the rebuilt from Rich several years ago, more than a few local owners have brough their brains by here to test in my car. Several others have even had that brain to test in their car when they were stranded on the road, or even in their own garage locally. When I get the original one reworked and returned, it will go back in the car to free up my 'spare' again for this same duty. IIRC, there are several folks around the country who keep rebulit brains for John Speake, a site sponsor. Don't know if they loan them out under controlled circumstances or not.

I'd also like to remind folks that LH failure is a matter of "when", not "if". My car has lived a rather luxurious life, stored in a climate-controlled garage, living in an area that has very low humidity, and doesn't see temperature extremes, etc. Those are factors that theoretically affect the service life of electronic bits in the brain. Mine lasted 20 years. Yours may last longer, may not. But it will fail. It may be a gentle, gradual failure that doesn't really strand you, or it may be an instant issue where the car suddenly just won't run at all. If you start to see symptoms like loss of power, increased fuel consumption, sometimes hard to start, these can easily be early signs of LH Alzheimer's. Good news is that a rebuilt brain is available. If you are fortunate enough to live close to a holder of a rebuilt brain, it takes only minutes to swap connectors and find out for sure. I know I could have easily spent lots of hours diagnosing all the 'normal' stuff before biting the $bullet and sending mine for rebuild.

My years-ago investment finally paid off. I wanted to share the story of the symptoms and the cure I found in the 928 medicine chest.

----

To Tom's question:

Yes, there is a way to test out of the car. But you can test locally by swapping yours into a car that is known to run well. An understanding owner might allow you to borrow a brain to try in your car if the results of the initial swap aren't conclusive. IIRC, Rich's builder has a test fixture to simulate the sensor inputs and signals needed to test the brain. I believe John Speake has a similar setup for testing. Contact them to discuss options, or maybe they will jump into the discussion here to share their thoughts and suggestions.

Tom. M

Thanks Dr. Bob...

I had my GT brain along just in case my track car decided to act up. Unfortunately, I can't be 100% positive the LH and EZK are properly wired in my 82 track car (91 motor- with old panel)...and the EZK as far as I can tell is getting constant power. There may be an issue the the relay's/wires..or the brain may be bad..
When it goes bad the car seems to run rich and can't hold idle. When it did this, I swapped in the GT's EZK..no change....still rough running. Then I swapped in the GT's LH..and car ran smooth. So this points to the LH...but...before I get it rebuilt, I'm going through the wiring..and will also try the 91 brains in the GT to see what happens.. It would be cool if Rich or someone could just plug the LH into a test rig and duty cycle it...and say ..Yep...this or that is bad...

Lizard928

I wouldn't say for sure it is the LH Tom, however has it happened since we put the GT brain in?

Tom. M

I've only driven it once with the GT brain since then (it ran fine), so I can't really say. In a couple of weeks I'm going to put the porkensioner on the GT and will bring the 91 brains to run in the GT. We'll see what it does.

Mike B

For those, like me, that were wondering... http://www.electronikrepair.com/home.html

dprantl

My car would intermittently run really rich. Since it has 30lb injectors, it would instantly kill the car and it would not start at all unless I removed the fuel pump relay and blew all the excess gas out of the engine with the starter. It turns out my TempII sensor was going bad.

Dan
'91 928GT S/C 475hp/460lb.ft

Tom. M

I just read some of the troubleshooting tips on Rich's site.... interesting about the fuel pump not working unless jumpered if the LH is bad. I was having issues with getting my fuel pump to run, and ended up wiring the relay to work off of the ign. switch. HMMM......things are starting to point to the LH...I'll keep looking...

the flyin' scotsman

..........and the other game in 'town' http://www.jdsporsche.com/index.html


Are we on this weekend Mike?............look @ that 928 the Edm folks spied.

dr bob

Seems like there are more than a couple symptoms that are indicators of LH failure. I thought mine idled OK with the old brain, but I was in denial a bit. New one is much smoother. In fact there were a lot of symptoms that, in hindsight, could have pointed me to the LH brain. They kinda snuck up slowly, so I didn't get excited about anything different. It wasn't until the hard starting with flooding symptoms that it started to get important. I hate getting stranded by stupid stuff, and hard starting like that isn't something that ever cures itself. At least in my limited experience.

Tom--

Send your brain to Rich, or to another vendor if you have a different preference, and just get it done. You know you want to. All your friends are doing it. And it will feel a whole lot better when you are done.

Tom. M

Yea...I know..it's only money ....I'll have to weather the sting of my track rims/tires first...but will probably bring it down with me to Sharktoberfest and talk to Rich there... who knows..maybe I'll win the grand prize at the dinner...(last few years it's been a free rebuild by Rich)