John Speake

My experience is that a non-start problem due to an faulty LH is most unlikely to be intermittant.

There are some LH faults which can cause intermittaant rich or weak running.

I've rebuilt over 600 LH ECUs.

Eturbo924

I do fear that is where I am headed.. the LH, but I need to run down all the other posibilities before I put out over $600 for a rebuilt unit.

Funny. Car started again today at lunch as I had hoped and I drove it home. I let it run for 10 minutes or so and it was fine. It stumbled down a couple hundred rpm once or twice but caught itself and ran fine. I restarted it three or four times to see and it started each time.

Ah love these intermittant issues.

Anyway on to the other grounds and checks tonight.

Think it makes any difference that I am diconnecting the batter when I let it sit? In other words clearing any error codes that might otherwise prevent the car from starting? (87 928S4)

John Speake

At present I would say your LH is most likely not the problem until you have ruled out all possible bad connections.

Have you cleaned the grounds near the ingition final output stages ?

Louie928

When my LH failed from the fuel pump relay non-grounding problem, it began as an intermittent. It got worse in spite of doing all the fuse cleaning, grounding, coil wire checking, etc. If you can possibly get another LH to try for a few days that should tell the story.

A JDSPorsche rebuilt LH is $495.00, not $600.

The_Remora

Eric, sounds a bit like my car with the intermittent non-start problem. Sometimes these cars do seem possessed! I've just ordered a new ignition switch that I think should do the trick based on the fact that i've cleaned all the other grounds and can get the car to turn over if i put 12v to the where the starter relay is (my starter relay is permanently jumpered due to 5-speed conversion).

My LH is not verified to be 'good' but you'd be welcome to switch it out with yours to see if that makes a difference. I live in Boston but my car is currently on jack stands in Falmouth on Cape Cod while I'm working on it. I'll be down there Friday working on the 928, If your car is capable of driving down there you'd be welcome to try to do some work there and switch out the LH's. Otherwise my car should be back up in Boston next week and you;d be welcome to switch them out up there too if you still need to troubleshoot. Although the best thing would be to find an '87 LH taht was recently rebuilt by JDS cause maybe mines bad too and we'd just go around in circles

Question: when your car won't start, does it turn over and not fire up or do you get absolutely nothing when turning the ignition switch. Also, is your battery strong, because these cars are hard on batteries and if you have a weak battery that can cause all kinds of problems.

Eturbo924

Ok "Have you cleaned the grounds near the ingition final output stages ? " Do you mean at the coils? I have had both of those grounds off recently and did not note an bad corrosion... but those are both on the list to go back over tonight. Also inspecting the cap and rotors. (the ignition wires and plugs are new)

When starting my car... when it fails to start... the car turns over perfectly as if it was going to start but just does not fire any cylinders. When it does this I have jumpered the FP relay with no change and then the LH relay with no change. I did not jumper both at the same time.

The_Remora... I would not risk driving my car to work again, and that is only .6 miles away, before I figure out what is going on. AAA does not like to keep towing my car :-). But I had read about issues with the ignition switch and had felt maybe it could be a factor?

$495 is a bit better but until I can find some thing to give me a definate answer I would hate to spend that money... since I do not have it to spend at the moment.

John Speake

I'm refering to ground point MP III on page 10 of the circuit diagram, this is the grounds for the amplifiers and colis, not the big strap from coil to engine block.

Borrow a known good LH, then you don't have to spend $$$ to eliminate that possibility.

Eturbo924

Ok think I have given up.

Cleaned all of the component/connections that everyone has suggested... at least I think I did. I have to go back over my notes.

Cleaned both caps and rotors.

Started the car and it ran kind of poorly for a few minutes then cleared. It has been very damp and humid in this area... not sure that had anything to do with it but figured I would note that.

Anyway the car has run for a couple days now. Each time I cleaned and checked things I started it to make sure it was still working. Oh interesting note. When I pulled the fuse/relay block I found a loose screw in between the wires on the back. It was sitting in the area between the window and sunroof fuse connections. No doubt in my mind it had shorted the two. Now the sun roof and windows do not work. Any ideas on where these two systems might meet at a common connection that might have been fried by the shorting? Or might have come apart?

Also found a loose connection at the tail light fuse. Could explain why I had inttermittant rear light issues. Fixed that. I could not see or feel any other loose connections or issues.

So the car ran good all this time. Then decided I could do no more in that area and put it back together. Started the car... still running fine. Let it run a few minutes again. Then put the wood cap back on... and carpet in place. Weirdly when I started the car this time the idle was down 100 rpms and then the car died in about 30 sec after starting. It then fired right back up and died right away... never to start again.

Either I missed some thing in there or it was just about to die anyway.

I am done. Guess it is time to buy a rebuilt LH module. What is the contact information on the $495 unit?

The_Remora ... Let me know if you have made it back up to the Boston area. I could always bring my LH down to your car and see if it causes your car to act like mine when I put it in yours.

My car is dead in the driveway once again. Ah joys of 928 ownership I guess. At least the seats are comfortable in my giant paperweight. :-)

docmirror

Ignition switch.

Swap LH before commiting to rebuild.

John Speake

If you confirm with a loaner that the LH is the problem, then Louie Ott stocks my rebuilds...

http://www.performance928.com/cgi-bi...&pass_parent=0

Eturbo924

John ok thanks. I will try to get my LH into another car or some ones LH into mine soon to confirm.

Could you help me out with this "MP III on page 10 of the circuit diagram" Do you have a link that I can see. Visuals are always good :-). That is one I do not think I got yet... unless it just happened to be in sight and I cleaned it with out knowing it.

Thanks!

Eric

Eturbo924

Question
Would an 88 auto 928S4 be a good test vehicle? I know of one at a salvage yard local that I could take my LH to and see if it exhibits the same issues with that car. It is reported to run well so if my LH is bad it should cause the 88 to stall as well... right?

John Speake

It's the ground associated with the igntion output stages, they are shown in this excellent diagram from Tony's website....

http://members.rennlist.com/v1uhoh/underthe.htm

The grouds are nearby.

Yes, you can swap LH ECUs from/to any car 87-95 and it is fine for a test.

Eturbo924

Ok those are 9 and 10 in the diagram called ignition control unit correct?

There were a bunch of grounds there that I cleaned.

So looks like I got those.

Ordered a bunch of new relays and fuel filter. The car starts and runs and then dies every day after I let it sit. I think I discovered the relay in the EZK position is the wrong style. So crossing fingers that it is the issue. But... have little hope at this point.

Thanks!

Eric

Eturbo924

Quick update to the saga.
New ignition switch did not solve the issues. Tore down the old switch for the heck of it... it did not look too bad but no harm in replacing it. But I did screw up the bearings on the steering shaft... don't ask. :-(

So found some one local who I hope will allow me to put my LH comp into his car. That should give me the definative answer I am looking for. I hope. Just need to contact him... or him to contact me.

Stinks having a nice car and it just sitting in the car tent. Ah well.

Thanks Everyone

Eric