Mrmerlin

Does anyone have a good LH computer for a 1986.5 that they would like to sell,
I think i may need one for the car i am trying to get running.
Thanks Stan

supercedar

I sure wish I could help you. You are such a big help on this site.

Thomas

hacker-pschorr

If you come up short and need go move forward, I can loan you one of mine while yours gets fixed.

My "spare" will eventually be in my 79, which is why I need to keep it.

Have you popped the cover to take a peek? I had one with a burnt resistor, simple fix and if by some dumb luck it's the same resistor I purchased a few dozen

PRC928

I have one. PM sent.

Paul

Rod Underwood

Two sets on ebay right now, I believe. Don't have any idea of condition of course.

Good Luck,
Rod

Mike Frye

My spare is yours to borrow for as long as you need it (spare EZ as well if you like). Tested good.

Let me know and I can ship by Friday.

Mrmerlin

Thanks it looks like the owner is sending me another one from 928 INTL,
I have to do some other invesigation on why the LH might fail in the first place as it has already been replaced once.
Thanks for all of your kind offers, Stan

depami

What makes you think it is bad? What are symtoms? Just curious.

928DK

I have all the original wiring and LH+EZ from my 1987 S4 if you or anyone else is interested
(have TecGt now instead)

Bernhard
87 928 S4A Tungsten Silver
TEC-GT, numerous other mods

Mrmerlin

Denny the test port will not shut off the ISV and let the idle be adjusted, i got a PM that pointed out this fact that the LH is the computer that controls this function.

depami

^^^^^^^


I have no idea what you are talking about but thank you for responding. The reason I asked is because I am still fighting a “no start” condition on my 86.5.

The EZF was not sending an RPM signal to the LH. So, the LH shut down the fuel pump and the injectors.

The CPS is suspect but the last time I checked with a scope it was showing >2.4V PP AC.

I have been away from it for awhile but am now just getting back to it.

I will keep everyone infomed.

Mrmerlin

here is a link to the test port on the 85 86 engines
https://rennlist.com/forums/928-foru...usting+idle+86

John Speake

The LH control units for 85/86 are very reliable, so you are wise to find any possible external source of a problem like a short circuit..... on the idle valve or harness.

Mrmerlin

Just to update this,
I swapped in a another LH unit and the ICV can now be controlled
The issues were,
the car when cold would start and run rich, and the ICV circuit would operate as it should for about 2 mins while the engine was warming up after that it would stop functioning, it also was running rich
(IE jumping C and B terminals at the test port to test the function of the circuit )

After roughly 2 mins the ICV would not activate or deactivate via the test port , also the engine if shut off would not start again unless the pedal was floored and sometimes this wouldnt work.

During this repair MAF, ICV, O2 sensor , various vacuum lines all replaced with new parts
all the new parts were needed as the old parts were also all bad.

The LH had been previously replaced with another used part from a 928 vendor.
So it wasnt a question I thought.

I took the suspect LH and put it into another car and the problem transferred,
it would run for about 2 mins then the ICV circuit would stop functioning, and the hard start issue also followed the LH .

Re Hooking up the other cars computers and it started and ran properly.

John Speake

Hi Stan
I think in fact what was going srong was the O2 loop. So when water temp got near 80 deg after 2 mins, then the O2 loop should be activated, but in your case it was faulty.

Running very rich can be a sign of O2 loop failure.