Couple Qs, Idle dipping & PCV location

sv51macross · 06-06-2011, 08:13 PM

I've just flushed my coolant and replaced the ECT, hoping to get a little better mileage. Want to clean house a bit here and try and massage out another problem. After letting off the throttle, say when shifting into neutral to coast to a red light, the idle usually dips down to around 300-400, then returns to 700-800. It will also do this in the driveway, from any RPM. I take it that this is the IAC or BAC (or are those the same thing...

) acting-up, could it be a vacuum leak or just plain old actuators? I've to this point been adjusting idle with the screw atop the throttle body assembly, should I be adjusting the TPS?

Also, looking through the FSM has left me clueless as the the actual location of the PCV valve. The oil volume gradually increases (blowby, the seals are beginning to go) and at the same time I'm sure the evap isn't working. The diagram in the FSB shows the evap and PCV route through the same valve (IIRC, the FSM is in Lucy and my brother has her for the night). Where exactly is this bugger so I can replace it?

FRED · 06-07-2011, 04:05 PM

PVC is located on the rear end of that line of solenoids on the left side of the engine. Its called the PURGE VALVE and is made of black plastic and is close to the oil filter area. One hose on its top and two on its bottom. Page F1-70 of the FSM shows it. Fuel and Emissions section.

The BAC seems to be working on your car........mabe........so check the DASHPOT on the throttle linkage for being functional. Its shown in the FUEL AND EMISSIONS section of the FSM also.

Then again it could be BAC related. Idle the engine fully hot and then pull the elect plug off the BAC. Usually the idle will drop a bit doing that. Just a hundred or so drop. Then again if the idle was set near 800 rpm then the drop probably will not show up.

sv51macross · 06-15-2011, 02:47 PM

Got around to it, found the PCV (haven't done the throttle stuff yet). Tested it according to the FSM and it seems to work. How much vacuum is supposed to be generated though? It seemed kind of weak, covering the oil filler with my hand (and the PCV plugged back in), I couldn't really feel any change in pressure from idle to 2500 rpm.

RETed · 06-15-2011, 05:36 PM

If the engine is burning excessive oil, that might be the culprit to all your problems.
Excessive oil coats the spark plugs prematurely, and that will cause idle (dropping) problems.

-Ted

sv51macross · 06-16-2011, 12:11 AM

No excessive burning of oil, a quart of Lucas stabilizer during the last oil change fixed that (no more smoke @ high RPM yay!) I'm going to be checking the TPS and a couple other things as soon as I remember to buy a new battery for my DVOM.

RETed · 06-16-2011, 05:17 AM

Quote:

Originally Posted by sv51macross

No excessive burning of oil, a quart of Lucas stabilizer during the last oil change fixed that (no more smoke @ high RPM yay!)

Not necessarily a good thing...
That stuff basically just increases the viscosity of the oil.
Increasing the viscosity of the oil causes it to flow slower through the stock oil injection?
Assuming that's still intact...you're under lubricating your engine now.

-Ted

Pete_89T2 · 06-16-2011, 07:03 AM

^Roger that, recommend you run premix with the fuel as a precaution.

sv51macross · 06-16-2011, 10:07 AM

Quote:

Originally Posted by Pete_89T2

^Roger that, recommend you run premix with the fuel as a precaution.

1oz/gal ever since I replaced the oil injection lines. Kept checking them and 3 lines never filled, this was far before the Lucas.

06-06-2011, 08:13 PM	#1
sv51macross Rotary Fan in Training Join Date: Oct 2010 Location: Ann Arbor, Mi Posts: 47 Rep Power: 0	Couple Qs, Idle dipping & PCV location I've just flushed my coolant and replaced the ECT, hoping to get a little better mileage. Want to clean house a bit here and try and massage out another problem. After letting off the throttle, say when shifting into neutral to coast to a red light, the idle usually dips down to around 300-400, then returns to 700-800. It will also do this in the driveway, from any RPM. I take it that this is the IAC or BAC (or are those the same thing... ) acting-up, could it be a vacuum leak or just plain old actuators? I've to this point been adjusting idle with the screw atop the throttle body assembly, should I be adjusting the TPS? Also, looking through the FSM has left me clueless as the the actual location of the PCV valve. The oil volume gradually increases (blowby, the seals are beginning to go) and at the same time I'm sure the evap isn't working. The diagram in the FSB shows the evap and PCV route through the same valve (IIRC, the FSM is in Lucy and my brother has her for the night). Where exactly is this bugger so I can replace it? __________________ 1990 Mazda RX-7 NA; Lucy, after the main antagonist from Elfin Lied. Eventual plans? Something cyberpunk and spicy. Last edited by sv51macross; 06-06-2011 at 09:33 PM.

06-15-2011, 02:47 PM	#3
sv51macross Rotary Fan in Training Join Date: Oct 2010 Location: Ann Arbor, Mi Posts: 47 Rep Power: 0	Got around to it, found the PCV (haven't done the throttle stuff yet). Tested it according to the FSM and it seems to work. How much vacuum is supposed to be generated though? It seemed kind of weak, covering the oil filler with my hand (and the PCV plugged back in), I couldn't really feel any change in pressure from idle to 2500 rpm. __________________ 1990 Mazda RX-7 NA; Lucy, after the main antagonist from Elfin Lied. Eventual plans? Something cyberpunk and spicy.

06-16-2011, 12:11 AM	#5
sv51macross Rotary Fan in Training Join Date: Oct 2010 Location: Ann Arbor, Mi Posts: 47 Rep Power: 0	No excessive burning of oil, a quart of Lucas stabilizer during the last oil change fixed that (no more smoke @ high RPM yay!) I'm going to be checking the TPS and a couple other things as soon as I remember to buy a new battery for my DVOM. __________________ 1990 Mazda RX-7 NA; Lucy, after the main antagonist from Elfin Lied. Eventual plans? Something cyberpunk and spicy.

06-07-2011, 04:05 PM	#2
FRED Rotary Fan in Training Join Date: Mar 2011 Posts: 73 Rep Power: 15	PVC is located on the rear end of that line of solenoids on the left side of the engine. Its called the PURGE VALVE and is made of black plastic and is close to the oil filter area. One hose on its top and two on its bottom. Page F1-70 of the FSM shows it. Fuel and Emissions section. The BAC seems to be working on your car........mabe........so check the DASHPOT on the throttle linkage for being functional. Its shown in the FUEL AND EMISSIONS section of the FSM also. Then again it could be BAC related. Idle the engine fully hot and then pull the elect plug off the BAC. Usually the idle will drop a bit doing that. Just a hundred or so drop. Then again if the idle was set near 800 rpm then the drop probably will not show up.

06-16-2011, 07:03 AM	#7
Pete_89T2 Lifetime Rotorhead Join Date: Apr 2010 Location: Elkton, MD Posts: 874 Rep Power: 16	^Roger that, recommend you run premix with the fuel as a precaution.