idle problem

referee1 · referee1's Garage

I bought this 83SC just this past February. I love it. It runs really well and has an unbelievable sound. I had to put a starter on it and detail it a little and that has been about it. BUT,

I drove it all day last Friday and all was well. Saturday I started it up and it didn't want to idle. It sounded, well, kind of "muddy". Almost like it was under water. I I could keep the engine running by pumping the accelerator a bit, but it would never really rev up. It was also snapping and popping, almost like a backfire but not quite as loud. It ran fine after about 90 seconds of this behavior. I figured it was bad gas, got some gas treatment, and didn't see the problem for the rest of the day. Even went down on Sunday and it started up fine. This morning the problem was back, but again I worked through it and it ran fine all day. Going to try again in the morning and see how it does. Anybody else ever heard/experiened anything like this? Thanks for helping a 911 newbie.

kqw · 06-08-2004, 08:06 PM

Are you in Ohio by any chance????

kqw · 06-08-2004, 08:21 PM

It's going to drive you crazy however, This may assist you....

2 weeks ago I filled up in Ohio retuning to Eastern PA. The next morning, I had the same issue you have.

I had the time so I ran injector cleaner through a tank of gas, replaced, The CHT, ICV and O2 sensor. Cleaned the Speed and ref. Sensors, all connector plugs cleaned and reset the idle.

I must say the idle was smooth as silk. The next morning, same thing. Stumbling for about 10 sec's and then running fine.

In the last few days, the problem is slowly going away.....

IT HAD TO BE BAD GAS.......I would run some techron through your tank and give it a couple of days.

referee1 · referee1's Garage

Thanks for the help. The must be REALLY bad gas. I have some Techron in the garage. Can't think of a better time to use it than now. You mentioned getting your idle smooth. The idle I have always experienced with my car is kind of a "thrum". Not really a hunt, but speed up/slow down of maybe one hundred rpm. I am determined to learn how to work on this machine. Maybe the idle is a good place to start. Thanks again.

Graham Archer · 06-09-2004, 07:03 AM

It sounds like you need to adjust the mixture screw on the fuel distributer.

Paulporsche · 06-09-2004, 07:46 AM

Check out threads regarding WUR, AAR and AAV, and vacuum leaks. My guess is your control pressure is too high at start (running too lean) and you are too rich when warmed up, causing the fluctuating idle. Do you have a popoff valve in your airbox?

Good luck and keep us informed.

Paul

referee1 · referee1's Garage

Thanks for all the replies. The car IS running rich when it is warm. You can smell it. When it is cold, it actually starts faster than when it is warm. It fires right up cold, but cranks a few more seconds warm. I do have a popoff valve installed. This motor was rebuilt by a place called Motor Meister in California, probably about a year ago, to the tune of almost $12,000. Upgrade this, polish that, and turbo this other thing. It is an impressive list. As for those other things (WUR, AAR, and AAV), I have to figure out what those are first, but one of my mechanics did mention it could be a vacuum leak.
As a side question, when I jack the car up, where can I support it with jack stands? When I got up under it and looked, it seemed like I could potentially damage quite a few things. Don't want to injure it, now.
Thanks again for the help. I will look for those articles.

LFogelson · LFogelson's Garage

Something similar once happened to me.... the oil cap wasn't well aligned and caused a vacuum leak. I found it when I wanted to test for a vacuum leak... idle should drop when the cap is removed. Also a similar problem can happen if your frequency valve relay is going bad (the relay under the passenger seat). Good luck.

stlrj · 06-10-2004, 01:32 PM

I had similar symptoms when my 02 sensor or my ignition cablels got wet.

Cheers,

Joe

referee1 · referee1's Garage

Hey! I was wondering what that box was under the seat. Are those still available? It looks like something I could do on my own, anyway. I am going to have to read up on all this stuff so I will understand the things you guys are telling me about. For now, I am looking for the idle adjustment (it idles at about 500) to bump that up a bit. I believe it is supposed to idle just under 1000 rpm.
Thanks again.

fstar · 06-12-2004, 06:00 AM

ALL my idle issues vanished when I disconnected my O2 sensor.

azasadny · azasadny's Garage

referee1,

Sounds like you could ude our hosts's book "101 Projects for Your 911", as it explains how to jack the car up, basic projects and useful knowledge. When I bought my '71 911 two years ago, that was one of the first things I did and I'm glad! Besides the book, spend some time searching old posts here and you'll get all of your questions answered. Good luck!

referee1 · referee1's Garage

Thanks! Just ordered the book.

scottb · 06-12-2004, 10:22 AM

Quote:

Originally posted by referee1
This motor was rebuilt by a place called Motor Meister in California.

Yikes!

Do a search on the board for "Motor Meister". Therein could be your problem.

LFogelson · LFogelson's Garage

There are two boxes under the passenger seat the large one is the lambda computer (02 sensor computer). The small one is the frequency valve relay. These are available from our host, but I bought one in the past from NAPA. Try and unplug the relay while the car is running. If the idle doesn't change then the relay is bad. Unplugged the car should run very rough like you are describing.

referee1 · referee1's Garage

EEK! Well, at least I didn't spend my own money having it rebuilt, and I didn't have to deal with any of the rebuilders, either. The car runs well regardless (even a couple of my 911 buddies were impressed). I am sorry that company gets such a bad rap, but you kind of earn that, don't you?

I will try unplugging that relay tonight and see if it affects anything.

Thanks guys.

referee1 · referee1's Garage

Hi
I actually managed to follow the advice in some of these posts. That along with "101 Projects for Your 911" arriving, kind of helped me adjust my idle. I really appreciate all the help, but of course actually working on the car just leads to more questions.

I turned to mixture screw counter-clockwise (which I read would lean the mixture) and the idle got worse to the point that the engine almost died. I turned it clockwise (richen?) and the idle seemed to improve quite a bit. It improved to the point that the idle settled at about 950 and the backfiring, popping, and snorting (especially on a downshift) stopped altogether. BUT, when I unplugged the frequency valve relay, nothing changed. The idle didn't roughen, and the car ran fine with it unplugged. Not sure exactly what that means. Might it mean that I need a new FVR and then will have to re-adjust the mixture again?

I highly recommend the project book by Wayne. I have learned some things and found some things I would like to do, and I just got the book this afternoon!

Thanks again.

referee1 · referee1's Garage

Tooth911 · 06-19-2004, 07:29 AM

Wecome to the wonderful world of CIS .Ive had lots of grief with those issues. on my 77 911s although obviously no O2 sensor on a 77 but cis is a PTA ! one one of the best ways to learn and correctly diagnose would be to put a sniffer in the tail pipe at shop or a buddy who has one so you know your fuel setting is correct IE rich or lean. observing all this for yourself would be an eyeopener and you could get better acquinted with all the adjustments.

referee1 · referee1's Garage

Thanks,
I am trying to get a handle on all the helpful devices I can borrow/buy to dianose this stuff. It seems CIS has quite a learning curve, from the posts I read. Looks like I might have to go back to my Wrench, since he probably has all that stuff.