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86 928s 32v vacuum question and air valve question
On the throttle body the 2 ports closest to the firewall I've seen a few different diagrams not sure which to follow one is slightly larger than the other are they both used does one get plugged or what. When taking apart the larger was capped but most schematics show both used and the larger going to the main splitter while the smaller went to the thermo switch. Idle speed regulator on cold start up how long until it should drop down to regular idle mine seems like it's always a bit high but if I disconnect it and apply 12v I can get my low idle.
I believe one of the ports are for California cars. Idle control may be stuck, many have sprayed wd-40 or such to free it up. On mine I disassembled and cleaned.
From the schematics I've been going by the Calif. port is in the frt. on the driver's side. LOL I took mine apart too, regreased the shaft and siliconed any leaks. I checked the wires going back to the LH unit they're fine hooked an external 12v power supply it opens and closes freely was wondering maybe if throttle body has the butterfly set too far open maybe but it's a pain to get to on a I wonder. temp. sensors 1+2 check ok as well
"wondering maybe if throttle body has the butterfly set too far open maybe ..."
Yes it does have a set screw w/ lock nut and should not be adjusted, unless you know everything else is good.
You stated "..should drop down to regular idle mine seems like it's always a bit high but if I disconnect it and apply 12v I can get my low idle. ...".
Also note that the ISV is not an open or closed valve, the ECU "pulses" it very quickly and this could be a bad ECU ISV circuit, but most likely an ISV.
What exactly is a "bit high", does your tach work?
And yes all the sensors need to be checked for proper operation when cold and hot, their resistance changes.
I checked temp. sensors 1+2 both cold and hot and were both in their allowed limits. From a cold start it fires right up after a few minutes drops down and then just sitting there it idles up by itself I'm sayin' what the F is this thing possessed. At that point if you give it gas it revs up drops down to maybe 1500 then drops down a bit more but not all the way down. Then if I disconnect idle speed regulator and apply 12v idle comes all the way down, and with it disconnected you romp on it and rpms come right down. Tomorrow I'll get exact rpm's and times of oddity.
On the throttle body the 2 ports closest to the firewall I've seen a few different diagrams not sure which to follow one is slightly larger than the other are they both used does one get plugged or what.
When taking apart the larger was capped but most schematics show both used and the larger going to the main splitter while the smaller went to the thermo switch.....
The two on the Firewall side should be both used, the Larger one (variable vacuum) goes to the splitter so the Fuel pressure, Auto trans, and ECU's see's & knows the vacuum has changed per engine load.
The smaller one (constant) feeds the thremO switch supplying vacuum for the Fuel Tank venting system.
Thanks that's how I put them, on disassembly the larger one was capped and everything ran off the smaller port. today started the car, initially rpm went to 1400 or so then down to 1000 rpm at 2 1/2 minutes where it stayed for 17 minutes at that time engine was 190 degrees, then I revved it up and rpm stays at 1600 and won't go down unless air valve is disconnected and energized to close the air valve tomorrow will check throttle valve switch
12-08-2014, 11:06 PM
86 928s 32v vacuum question and air valve question
