Interesting both posts. Glad I'm not alone. I've also wondered if its the tuning on my PowerFC. Steve Kan is tuning my car at the end of March so I'm hoping that clears up the hesitation/hiccup I get. We'll see about the idle though...

 

Crap, new development in my problem. Today my car started idling really badly, down at about 500rpm and backfiring upon decel. Other than that it runs great, pulls smooth and hard. I am going to pull the UIM off in the morning and hopefully find something that came loose and is causing me problems.

 

So, anyone actually fix this problem? It seems like the symtoms are common enough that someone would have found what was causing it and fixed it.
Who has replaced the ISC?

 

Nothing yet on my end. I'm not going to touch anything till after Steve kan tunes my car. I think/hope part of my particular problem may be some fine tuning. I'll report back though.

 

Hey guys.

Car dies when cold -> Water temp fuel-enrichment setting.

Do a search on "water enrichment" and you'll find the answers you need. This has happened to others as well - including myself.

Also, remember the F/C section in the PFC rev screen specifies the pre-idle return speed when letting off throttle.

 

Well, steve did tune my car. Not much he could do there so don't get your hopes up to high.
Good point on the enrichment v. water temp, that could solve the problem when cold. What about the rest, it has nothing to do with the pre idle return speed on my car. No matter where I put that same result.

 

I sprayed alot of electrical parts cleaner all over the throttle body, anything that looked like it could possibly get gummed up got sprayed and cleaned. Runs good again and now back to just having the original problem.

The last couple nights when it was really cold the return to idle seems even more likely to stall the car than when it is warm out. Regardless of water temps, seems at least partially dependent on ambient temps.

 

Tom93,

Reset the PFC.
Redo the idle calibration.

What's your vacuum at idle?

 

hmmm, pfcs arent to great when temp changes too much, they just dont cope very well at all, actually pfcs arent the greatest choice on rotaries at all

 

Thanks for the tip HEns. I guess I'll just get rid of my pfc.

 

Clayne, thanks for the input, but I searched ALL forums and couldn't find anything related to water enrichment or water temp fuel enrichment. Do you have a specific thread that you can point us to?

Is the basic concept that the PFC or something is adding too much fuel at cold idle?

Thanks.

 

Anyone with strange idle. First try the idle adjustment by the book. Check the Idle air bleed screw, under angle pipe, is clean. If you can't tell shoot some carb cleaner in there while running. Then do the idle procedure, PFC or not. Make sure the idle speed screw on front of the TB is backed off to where the original white paint mark is a close to no action. Then start the procedure as per book Section F-16 to 17. Make the jumper out of an unbent paperclip, careful to get the correct pins. I have sometimes had to do this twice to get the idle stable in gear with clutch and in neutral. Note you don't need the SST. The jumper stops ECU control of idle. Once this is set and the jumper is removed then you can dial in the idle speed you want (PFC). Good luck!

 

Reset the PFC already, didnt change anything.
Idle calibration? Do you have a link? Or I will search on it in a couple days when I get home from my vacation as it must be somewhere already on the forum.
Up here in CO at about 6000 feet the idle vaccuum is only about 12-13. I believe it was closer to 14-15 when back home in Phoenix.

I also should try out the stock ECU again now with the ISC unplugged and the throttle body all cleaned up.

 

Tom93,

Reconnect the ISC.
Close bleed screw under elbow leaving only about a 1/4 turn.
Dial out throttle linkage screw on top to have no pre-load on the linkage at all.
Reset PFC.

Do the 30 minute calibration.

10 minutes normal.
10 minutes A/C on.
10 minutes defrost on.

I have personally seen a PFC emulate a vacuum leak type situation around idle because I had not done the initial idle calibration after doing extensive changes to the car.

 

Here you go man:

https://www.rx7club.com/showthread.p...hreadid=199148
https://www.rx7club.com/forum/showth...hreadid=121101
https://www.rx7club.com/showthread.p...hreadid=205241

 

I had a similar problem when car was cold, it would stall w/clutch in & revs dropping. It was a bad Clutch switch. This can be seen if you have a PFC commander. Go to ETC>sensor & sw. settings.> 2nd column, 5th row down is CLH or something like dat . 'Clutch in' shows a black dot.
Easy to check anyway.

 

Amazing, it seems that this may have fixed my problems. After about 30 minutes of driving around last night still no problems. Why would my PFC suddenly forget how to idle? Why did I never have to do this before when I reset the PFC? I wonder if the stock ECU works now, it had the idle problem also but that was before I cleaned off the throttle body.

 

Well if you reset the PFC you almost always have to do the idle recalibration routine afterwards. That being said, you mentioned surging with the stock ECU as well - which would indicate some form of vacuum leak etc.

It's fairly common for people to have calibrated a PFC to an engine with a slight or intermittent vacuum issue and then later they change something and the PFC doesn't relearn the idle routine - starting the surging symptoms. First thing that typically happens is to go searching for control system or vacuum leaks, not even suspecting the PFC needs to be recalibrated due to a previous change, etc.

For instance, after removing all emissions and going non-seq I had a very annoying 200 rpm surge at 1100 rpm. I think I spent about a week trying all sorts of troubleshooting routines to solve it with no solution; until I did my PFC idle calibration on a whim. Once I did that, the surge went away. Logically it makes sense as the PFC doesn't have the proper idle calibration for your specific car after resetting it, but it's close enough to let the car run.

Funny part is a week later I blew 4 vacuum caps (vinyl, do not use vinyl, use rubber or silicone) off my UIM and an annoying 1000-1500 rpm surge started up - but this time there was a real issue.

 

Thanks Clayne!

I think this thread might be the one to fix my issue: https://www.rx7club.com/showthread.p...hreadid=205241

Given that my battery was removed a few times recently to replace an FPD and the IC duct, I think that I might need to do the PFC recalibration also.

 

I have this idle problem on stock ECU so this isn't just PFC related. Rather than when it is cold I have this issue after the car warms up. If I drive for an hour or so, pull into my driveway and sit sometimes the idle will drop down to the 100-200rpm range and it would probably stall if I didn't step on the gas. It doesn't do it over and over though and it is infrequent (not everytime I pull in the driveway after extended driving).

I have a HKS EVC IV that monitors vacuum and on normal 800 rpm warm idle I'm around 375-425 (depending on outside temp/pressure). When it drops down and nearly stalls vacuum drops to 325 or so. This has also happened on E/L 1100 rpm idle. Other than the random hiccups the idles are smooth and steady.

Does the AWS or ISC effect/change vacuum levels depending on their settings/readings/valves? (I don't know much about them at all.)

 

Idle rpm affects vacuum levels, period.

375 @ 800 rpm idle is not healthy, I would check the system for vacuum leaks first.

 

I know this is an old post, but I was having a similar problem and like whiplash stated above, it was my clutch switch. Driving along with the revs in the 3000+ rpm range, push in the clutch and it dies. Runs fine otherwise.

Just a little FYI for someone searching in the furture.


Also, if you have this problem and you don't have a pfc, turn the cruise on and puch in the clutch. If your switch is good, the rpms will drop. If it's bad they will slowly creep up. Obviously, be careful with this test.