the flyin' scotsman

My adventure on this journey was to have my MAF evaluated by John S and the subsequent replacement thereof with a rebuilt unit. That was this Spring, I then replaced the Cats with Motorsports X and a new O2 sensor. I've also performed the WD40 trick to the ISV.

My proactive reasoning is posted...............by the way my 'stinky' exhaust smaell is gone, I blame the old Cats!

Rich9928p

Exactly!! Being eaten by grizzlies isn't my idea of a fun drive. Parts are replaced on aircraft by hours or cycles as preventative maintenance - falling out of the sky hurts. It hurts too when your 928 is not running and it is a cold dark night.

Either the module is tested in your car, or it is tested on a bench with devices that stimulate the LH as the inputs do in the car. Outputs are observed to see if it is doing what it should be doing based upon what goes into it - this is the "test jig" that was referenced. If it isn't working correctly, a repair is initiated.

However, a test is only as good as what happens at that instant. Some bugs are intermittent - if they don't raise their ugly head when you're looking - you don't see them. You also could be a day, week, or month away from the hybrid failing, and no test can catch that. Not all modules fail, certainly 50% aren't failing, but more than predicted by the normal "failure curve" are failing. So, the decision is yours. Test it, fix it if it is bad, wait for it to fail WHEN IT DECIDES TO FAIL, or fix it before it fails.

Brent 89-GT

I was somewhat lucky when mine failed. I was 250 miles from home but only 6 miles from a friends house. The next day I was planning on another 1000 miles across Nebraska, South Dakota and Minnesota. I could have been stranded and paying for towing, hotels and just plain wasted time. In that context a preemptive rebuild is not so absurd. I would not have considered such a thing myself but, when it goes, there you are.

the flyin' scotsman

Rich.......excellent response.

So in the dead of the upcoming winter my LH brain can be evaluated under the test conditions and repaired if required. Further to this repair there are updates that can be applied as preventive maintenance such as the suggested 'hybrid'. Are there other components that may fail?

fraggle

What does a "rebuild" really entail? Component replacement on the board or jst re-soldiering the zillion little circuits praying you don't burn something up (best left to professionals)

John Speake

Besides replacing the hybrid with a much more rugged version, I replace other parts which are at the end of their servicable life.

The unit is then put through a full functional test on a dedicated test jig.

The time to failure of these units is of course a variable. But judging from what I have seen of failed units sent to me over the last 3 years, I am getting progressively later and later MY units. When I started, I rarely saw 90-91 MY. Now they are common.

So I reckon anything over about 15 years and you are on borowed time.....

If the unit is abused then this time can be drastically reduced.

FlyingDog

How many rebuilds do you get that have already been rebuilt?

John Speake

Hi Matt,
None, if you mean rebuilt and fixed correctly

I do often get the results of "repairers" who hopefully resolder a few joints, and give up. Every time I receive an LH where the lid has already been removed, I hope they haven't done any real damage in there.

I did have one where a "repairer " had fitted the tile from a Volvo LH 2.4 - needless to say it wasn't working.

I always replace the tile, even if the fault is something else (which sometimes it is). I wouldn't put my name to an LH that didn't have the replacement tile.

the flyin' scotsman

John.............thanks also for your input.

BTW your web site is down again.............

John Speake

Hi Malcolm,
Ok - no problem, ask any questions...

Yes website has been down a couple of days, a hacker managed to get into my ISP :-(

People can always PM me....

When do you put your 928 away for the winter, and when does it emerge again ?

Regards

Lorenfb

"So in the dead of the upcoming winter my LH brain can be evaluated under the test conditions and repaired if required."

No! That's not really true. There are many limitations of a bench test, one of which
is for potential failures and/or intermittents.

Avoid being OVER-SOLD on parts replacements. Rennlist is here to help members
and NOT to "push" unneeded parts!

Taking the view of some on this thread & 928 problems one should IMMEDIATELY replace:

1. the water pump - weak
2. the early alternators - pre '84
3. the climate control unit
4. the MAF
6. the timing belt
7. etc., etc. & etc.

John Speake

Laren,
Malcolm and others are quite capable of deciding their own particular strategies of vehicle maintainance.

Neither myself not Rich have said "you must have your LH rebuilt, even when it is working OK at present".

I have had a few people decide themselves on the "preventitive maintainance" option. The other 97% decide to wait.

the flyin' scotsman

John............it snowed 2 days ago and day time temps are currently 5C. It wont be long before she goes into the deep sleep and re-emerges March ish although we can get some serious snowfalls in that month. I'll pull the LH prior to the -30C weather so there fewer chances of breaking frigid wires etc.

the flyin' scotsman

Loren............nobody is over-selling me anything.

I have a 20 year career in hi-tech telecommunications where most systems run in parallel to a back up systems known as redundancy as the teleco providers realise there 'can and will' be failures. After all how many laptops/ desktops do you believe would lasy 17 years of road going punishment without being repaired

My thread is as John mentions my preventive maintenance. Everything on your list and a lot more has been done since I've owned my car by myself. If your decision or anyone else on the list decides to wait for absolute LH failure then thats your perogative as it is mine to do otherwise.

John Speake

Hello Malcolm,
Sounds like you have winters I am glad not to experience :-)


Garth,
I would store that spare LH ECU with some aluminium foil shorting the 35way conector pins together. I have heard of them dying when just stored on a shelf.

A friend of mine pulled an engine for a rebuild, the LH and EZk were left disconnected as the engine wiring loom was pulled out with the engine. A few weeks later they re-installed the engine, and in that time the LH had died.

Regards