EdwardNorth

Hey all,

My PFC has been great and my FD has never ran more beautifully, however there is one slight issue with it. If I go to the store, shut down after sitting for a few minute cool-down, and am in the store for a short time, when I come back out and start it up again, the idle will shooot up to about 3100, sit there for a few seconds, and then idle hunt. This lasts for about 10-15 more seconds and then I get a backfire and the RPM's drop right down to 800 (normal idle) and stay.

I've tried a few things, and the only idea I can come up with is that maybe my indicated water temperature has something to do with it? It seems that if it is over 100 degrees on the PFC when I try to start it up, it will do this. However, if it is in the 90s or below, it will NOT do this.

Note that I usually shut the car off right away when it shoots up to 3000+. Then if I let it sit for a second, and turn it back on, the indicated temp has dropped into the 90s and it will NOT do the high-rev-then-hunt BS.

What could be causing this? Like I said, the ONLY time it does this is during specific hot starts. If I let the car sit for only a couple minutes after shutting it off, and try to re-start, it won't do this. If I come back an hour later and re-start, it won't do this. But about 5-15 minutes or so after shutdown and it does this just about every time.

Thanks in advance for your thoughts and help!

FD_Newb_1974

The wires on your PFC need to be cut. I had the same problem. You think it's a warm start, however, it's really when the temp on the PFC reads 88c or greater.

CAr does it after sitting because of heat soak. One the coolant cycles, your temps drop back down to below 88c. Most of the time when on the highway you don't notice it because your car is > 2200 RPM And in gear.

Clip the 4 wires and your fine.

HYDOUKEN

iTrader: (1)

I have the same issue on my car and I have already cut my wires going to the PFC. The car rough idles after a warm start for a little bit and then you hear the idle correcting itself after 10 seconds or so and eventually the idle will smooth back out at 30 seconds or so. But mine never has gone up to 3000 rpm. Usually the rpm jumps from around 500 to 1200

EdwardNorth

Since my wires are all (re)connected, I figured I'd take it one thing at a time. My guess is that the AWS system is what's causing the car to do this after sitting off for a few minutes after a drive, since it can control what the throttle body is doing (right?).

So instead of cutting the respective wire, we reached back behind the intake mani and disconnected the AWS solenoid connector.

I took the car for a drive after that, then stopped at a store and left it off for a few minutes as usual. When I came back out, before starting the PFC was showing 109 degrees water temp from the heat soak (like usual). This time, however, it did NOT shoot up to 3000 upon starting. It went up to 1800 or so RPM, and quickly and smoothly settled down to 800+.

I will have to see it a few more times though before I know for sure that it's fixed.

I hope this helps anyone with the same problem.

sub-zero

Check the ISC it is junk with the PFC.

skotx

I've had a similar problem for quite some time, though mine never shot up to 3k rpm, it just idled very poorly and stumbled after a warm start. This occurred when temps were over 100C and settled down as water circulated and brought the temps down.

Are you saying that you reconnected the four wires that Apexi recommends clipping and then pulled the AWS solenoid? I wonder why clipping the wire wouldn't effectively disable the AWS?

Thanks for the info. I'll have to experiment more myself.

-Scott

EdwardNorth

No, I had an issue with the car not starting and not getting proper voltage indications on the PFC after clipping the wires during initial installation of the PFC. That's why I reconnected all of them, because I most likely cut one or two incorrect wires.

After reconnecting them all, I wish I never tried cutting them in the first place because the car runs BEAUTIFULLY with the wires still connected. Not rough at all, and it became a totally different FD compared to the stock ECU.

So long story short, the only issue I had was the afforementioned hot-start issue, so instead of going back in and re-clipping some wires, I tried disconnecting the AWS solenoid connector in the engine bay because I thought the AWS connection was causing this issue.

It hasn't had this issue once since I pulled the connector (3 hot starts and counting).

EdwardNorth

What is the ISC?

mr.zoom

iTrader: (1)

I just installed mine too and it is doing this also.

Is there any water temp corrections needed??

HYDOUKEN

iTrader: (1)

I will disconnect my AWS just to make sure. But I know i cut the correct wires. Any yes once the water temps go down the idle smooths out. I did have some adjustments to my water temp corrections but when winter came the car would rough idle so bad that it would stall. Since I switch back to the stcok settings that came with the PFC the car doesnt stall but rough idles when heat soaked

luizajeff

Those of you with the heat soaking, have you the fan mod (a fan mod)? I run my fans each time after I park and I have yet to have this prob. Otherwise, I just have the idle thing until my car warms up.

Stevey629

ok, I have this idle searching problem too, but unfortunately, mine will stall out when in the process. It will start up, hold steady at 1500 RPM, then drop down to 800 or so, and intermittently hop around 300 or 700 then just...bam. dead. I have to drive it, and stay above 1500 to avoid these surges, then once I have it running for a decent 5 minutes after going easy on it, it will be able to find the idle and won't die out. Its just at warm start up. If I know its warm, then I know its gonna be tough to drive in parking lots. Lots of using the parking brake and staying in the gas, clutch tricks to keep it running smoothly....

And even when its fully warm, coming to a complete stop concerns me. Its surges down to 200 RPM, nearly stalling, then picks itself up like its catching up. This is when it is running at "best" when warm.

Stevey629

Does anyone know what this is caused by? I find this occurs most often when the car has been run for a while, then sits until it is WARM, on its way to cooling off entirely. The crappy stock temp gauge (thats all I have at this point) will read a little above stone cold, and this is when the problem seems to be most evident.

Stevey629

ok, I think I need to get a boost gauge, or at least get a commander, because the only way that I can tell if I have boost, (if any) is the blow off valve. The boost doesn't seem very strong, but I have no idea what it is, let alone how the vacuum is acting either. I know for a FACT that after the first run (cold start, run the car then shut off sometime at destination) its great. Everything after that seems to let heat soak, high intake temps, or something just make the car bog out, seem very sluggish, and produce a much much quieter "blow off" sound. If you're going to tell me to get a boost gauge, I know. I really am trying to get one in the very near future. Otherwise, what would you recommend I could do in the mean time?

cewrx7r1

iTrader: (2)

An automated control system as is the PFC idle control that uses fuel, air and timing (ISC system), works within a narrow range of parameter specifications.

Air flow is one of these. If the combination of idle air flow that is controlled by the throttle set screw and the air bleed screw is already too much/little or and the edge, then oscillation can happen.


All you have to do is help the system out with manual adjustments. Trial and error.
You expect the ECU to do it all? Only in fantasy world or in multimillion dollar machinery. Grow up!

In layman's terms, tune the frigging idle. So many of you people have never learned any simple basic tuning of even a stock FD

This topic comes up so much, why don't you all do a search. After all the PFC has been here on the list since about 1999.

Stevey629

This is the thing though. I realize that there is a screw for the idle adjustment, but it doesn't seem to help it unless I hold it really high, i.e. above around 1300 RPM. Anything below that seems to want to make the motor bog out, and "search" around for an idle before it settles out. However, in appreciation for the post cewrx7r1, I was making the presumption that if the PFC was tuned professionally, this idle gremlin would have been sorted out...whether it is a mechanical or an electrical/ECU related issue. My complaint mostly lies in a warm start, followed by a COMPLETE stall all on its own. Idle fluctuation was merely something that I attributed to the stalling problem. And btw, I have tuned the idle screws and had others try to as well many many times before, and although it kept it from stalling, idling so high around 1500-1700 just didn't seem like a good idea to me.

Maybe this post should have been put in the 3rd Gen section instead, but I figured that this new problem would have something to do wtih the PFC. Excuse me for making such a "youngan" mistake.

cewrx7r1

iTrader: (2)

Turn off the O2 idle control. The idle control system was really designed for a stock engine. When you go modifying, it is out of range. It is then up to you to try ways to help it.

Some people even totally disconnect the ISC solenoid and adjust it totally manually.

I have my O2 controll off but my ISC still on and it works fine.


You have to STUDY these controlls and understand them in order to tune these cars!