interesting high start up idle fix

[semlin]

so i recently bought a second 80, and one of its interesting habits is that it idles at 500-600 rpm.

going through the bills from the previous owner i found a series of four invoices at a mechanic complaining about high start idle where they repeatedly tried adjusting the tps and iac. these culminate in the following invoice.

 

[Ebag333]

Wait.....

They're resetting the ECU every time the vehicle turns off?

*facepalm*

 

[semlin]

so i went looking in the relay box and i found an infidel intruder hiding in some electrical tape!

 

[semlin]

upon investigation it's a 30 amp bosch relay wired to interrupt the power feed line from the main efi relay to the ecm.

the relay is triggered by power from the same power line source as the efi relay so basically it is a second redundant efi relay. if it does not work, the ecm gets no power even if the efi relay is triggered and trying to send it.

i have no idea what this is supposed to do. mechanic placebo? i yanked it all out and rewrapped the harness. pretty annoying that they cut and spliced into the harness around the main relay.

so far it idles at 700 rpm as it should, but i am guessing that is just due to the ecm resetting. if it actually fixes the 500 rpm idle i will be puzzled to say the least.

 

[Frankencruiser]

Sometimes you just want to walk up to the PO and give them a slap right across the face.

When I bought mine I found they had replaced almost all the fuses in the fusebox with much larger ones. Like where a 15 amp should be they put a 30. What a great way to fix the problem.

Good luck sorting it out.

 

[Cannon88]

so i went looking in the relay box and i found an infidel intruder hiding in some electrical tape!

LMAO! That cracked me up for some reason.

 

[semlin]

at least i got a free relay out of it.

 

[semlin]

Wait.....

They're resetting the ECU every time the vehicle turns off?

*facepalm*

it took me a while for the penny to drop on this but i understand now what you are saying. i think this was their intent but i looked at the wiring diagram again and the wire they interrupted is on the permanently hot side of the efi relay leading back to the battery so it should be hot even if you pulled the factory efi relay. on this vehicle you can pull the relay to reset codes.

otoh, maybe i am missing something. we'll see if i am idling at 500 rpm...