lcdial

iTrader: (1)

All-

My FD has a couple issues related to the A/C that have eluded my search skills, so I thought I would just post them here to see if anyone has any thoughts:

Issue 1: When A/C is on, car will stall when coming out of gear
It's actually not quite that dire: if I put in the clutch with the RPM greater than, say 3000/3500, and don't immediately put put it back in gear, the revs will drop all the way to 0, and the car will stall -- sometimes. Sometimes, it will drop down to 0 (or close to it) and recover. I used the PFC to up the A/C idle to 1000 -- that seems to help, but not 100% and that shouldn't be the solution. With the A/C off, it doesn't have the stalling issue. Revs will drop quickly, but the car recovers better. I'd appreciate any thoughts. I did see an older post with similar behavior, but in that case, they just rushed to the conclusion that a rebuild was necessary -- that seems a bit extreme to me...

Issue 2: When the A/C is on, water temps just rise and rise
This one is exactly as it states. Driving around with no A/C, I see water temps in the 180's-low 190's. When the A/C is on, the temps just creep up and up into the 200's. I'll shut it off then, but I've let it run up to 230 before shutting the A/C off (temps dropped back down to 190s), so I don't think there's an equilibrium (In that case, it was a hot -- 100 degree F -- day on the highway, but I was cruising around 80mph). Is this normal? Anything I can do to mitigate this?

Oh, about the car:
-PFC and tune
-Upgraded intercooler and radiator;
-K&N cone filter intake; and
-RB dual tip exhaust.

Thanks!

arghx

iTrader: (3)

Do you have a stock clutch and flywheel?

What temperature are your fans turning on? These cars run really hot with the A/C on from the factory. 230 doesn't surprise me. From the factory, with the factory thermoswitch, the fans don't turn to max speed until 220.

cewrx7r1

iTrader: (2)

Your PFC is not properly set up. And to properly setup the PFC, you need a DATALOGIT. The idle speeds can be changed with the Commander and a screwdriver. The FAN Speeds requires a Datalogit.


Find someone in your area and pay them to help you.

mdp

For Issue #1, I would check the TPS, but it could also be the dashpot. The dashpot's main function is to slow the throttle movement down when you quickly let off the gas. If the throttle snaps shut too fast it can cause the car to stall. Check out this post

The factory service manual has a procedure for checking the dashpot's functionality and it's adjustment.

lcdial

iTrader: (1)

Thanks all. You've given me some leads. As to the question: the car does have a lightened flywheel and an upgraded clutch. Would that change things?


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adam c

iTrader: (2)

The pfc has a setting where you can increase the amount of gas that the engine gets upon deceleration. I adjusted mine years ago to help with this same issue. Someone else is going to have to chime in here, because I dont remember the specifics for this adjustment.

You need to make sure your fans are operating properly. The first thing I would do is to check that the fan relays (on the passenger side of the engine compartment) are all plugged in completely.

lcdial

iTrader: (1)

Thanks. That's helpful. I'll dig through the PFC manual (as intimidating as that is). That may lead to me posting a few more questions, since I don't really want to blow anything up.

My fans are working. I can't say for sure if the temperature switch works, but they've been wired into the console, so I can turn them on manually (which I do). The temps rise when the AC is on even when the fans are also on. On a related note, I've recently read that I should turn them off when I hit 30mph (which I will do going forward).

Weirdly, when I first turn on the fans, the temps always go up a few degrees before coming down. I figured that had to do with the increased electrical load, so I've not worried about it.

lcdial

iTrader: (1)

Dale C-

Thanks for the pointer on the PFC. Below is a screenshot of the page of the manual where deceleration fuel cut recovery can be set. That seems very promising. I'll give that a try and report back.



​​​​​​Assuming making these adjustments can fix this, any thoughts as to what caused it to require adjustment?

Thanks!

arghx

iTrader: (3)

With stock clutch and flywheel, when you press the clutch pedal in the rpms drop slower than with a lighter flywheel and a performance clutch. That's a major reason behind the stalling.

I have covered extensively stuff about idle stalling or idle sticking with a PFC.

there's a big thread I made: https://www.rx7club.com/3rd-generati...needed-841706/

especially posts 1, 23, 27, 28, 36 cover idle

The decel fuel cut setting, the idle speed setting, the dashpot adjustment, and the idle air bleed screw, and the throttle stopper screw, and the fast idle cam... kind of makes you wonder why people look back at cable operated throttles with rose colored glasses.

I honestly don't think you're going to get the engine to run cooler unless there is some major mechanical problem like a failing water pump. These cars run really hot with the A/C on when they were brand new. It's just an "ignorance is bliss" thing with the stock temperature gauge.

lcdial

iTrader: (1)

So, I wanted to post the (hopeful) resolution here for posterity:

On the PowerFC Commander, I upped the deceleration fuel cutoff with AC from 1200 to 1350. That seems to have smoothed it out a bit -- at least keeping revs above 0 on rapid decel. It'll take some more driving to confirm its a solid fix, but it seems promising so far...

On the A/C temps -- is that the consensus view, that the engine will just run hot with A/C on? Anyone have alternative experience?

Thanks!

adam c

iTrader: (2)

Glad that fix is helping.

I would run the fans all the time with the AC on, irregardless of the speed you are driving. Check to see that the fans are running on high speed. Low speed fan operation wont be as effective.

mdp

As a contrary data point, my low mileage almost completely stock car, with a linearized temperature gauge, the coolant temperature around town in summer typically runs at 220F. If I turn on the air conditioner, to kick the fans on, the temperature drops to 185 and stays there as long as the air conditioner is running (this is just above the 177 - 182 opening temperature of the thermostat). In San Diego the ambient temperature is around 80F to 85F in summer.
Bear in mind that your PowerFC is getting its temperature in a different location than the stock gauge sensor. Also, this is on a car that has had its coolant changed once a year since 1994, had the fan recall performed, and still has the original thermostat.