Is this a dead alternator?

[Izzy]

james, the MAF is on the airbox itself. When you replaced the airbox, did you remember to connect the cable back into it? it is the connector right above the K&N sticker in this picture

Edited August 24, 2008 by Izzy

[jamesgood72]

Thanks Izzy. I have plugged in the electrical connector on my airbox, although it is quite a different design (stock) to the one in your picture. Would a failed MAF likely cause my engines inability to idle do you think?

-James.

[jamesgood72]

I cleaned the MAF this morning (following this : http://www.6speedonline.com/forums/996turb...f-cleaning.html ) and there is no difference. In fact, there is no difference if I completely unplug the MAF connection.

The car does seem to run fine if I keep my foot on the accelerator to keep the engine above 800 rpm. Let it go below that, and it seems to have problems, but that sounds normal to me. Where is the idle speed positioner?

So - how do you adjust the idle speed on a 996 C2? And how could it have changed after fitting a new alternator? I have done the reset by turning the key to the on position for at least 1 minute and then off for 10 seconds. That also didn't seem to help.

-James.

Edited August 24, 2008 by jamesgood72

[Izzy]

A couple of things you can do.

1. disconnect the battery for about 10 mins. Make sure you have the radio code to re-enter it. The computer should re-set after 10 mins and reconnect the battery.

2. Go to your nearest Autozone type store and ask to borrow a code reader. The codes stored on the DME should come up as to what is wrong.

I would do it in that order, as resetting the car costs nothing and you can do it at home. If you do get the codes, there is a code "decoder" on this site that can tell you what the issue is.

[jamesgood72]

I'll do the battery disconnect for 10 minutes. I just took it out for a 15 mile drive, all seemed good after I temporarily adjusted the height of the throttle stop by attaching a spacer to the top of it. It prevents the throttle from closing completely, the car idles much better, allowing it to be driven. I guess I'll have to take it in to see what they think. I'll get the codes read too, but I have no CEL on, so I assume there would be none?

Thanks for the help again, Izzy.

-James.

[demosan]

I'll do the battery disconnect for 10 minutes. I just took it out for a 15 mile drive, all seemed good after I temporarily adjusted the height of the throttle stop by attaching a spacer to the top of it. It prevents the throttle from closing completely, the car idles much better, allowing it to be driven. I guess I'll have to take it in to see what they think. I'll get the codes read too, but I have no CEL on, so I assume there would be none?

Thanks for the help again, Izzy.

-James.

James,

Your rough idle problem may have been caused by the low voltage to the DME as the alternator was dying. I assume you disconnected the battery when you replaced the alternator and now the DME has to "relearn" your driving habots as well as compensate for the "new alternator" putting 14+ volts into the battery for charging. As I recall, it takes approximately 5-6 starts for the DME to get itself back into "normal" ( I have read this in several posts in this forum). I would adjust the throttle linkage back to original position and let the DME do its thing in relearn for a few days and your rough idle should be eliminated. If not, then you go to codes for possible MAF issues.

Good Luck!! :cheers: demosan

[jamesgood72]

Thanks demosan. :thumbup: Does this relearning of the idle apply to my car - I have a '99 C2 which does not have the e throttle. I think this is the only 996 which has the wire cable for the throttle? I'll check for codes again today, but I still don't have a CEL light on, so I don't think there are any.

-James.

[Izzy]

James, it should apply to your car as well, I have had both 1999 and 2003 996's, same treatment for both. And I had codes without CEL as well, so just a precaution.

[jamesgood72]

I drove into work this morning (20 miles), and I noticed that the idle was way high (1500rpm!) with my little spacer on top of the idle adjustment screw. So - it looks as though things have sorted themselves out. I'll remove the spacer when I get home tonight - it looks to me as though the DME has adjusted things as you thought.

It's odd though, the fact that the car wouldn't keep running at first. I would start it, and it would do it's initial rev-up, then immediately stall. If I used the accelerator pedal to keep it at 1000rpm for a few minutes, as soon as I released the pedal - it would stall. Then, after I added in my spacer, and did that 20 mile first test drive, it still seemed to be the same. This morning, however, things look like they might be back to normal.

I hope so! I'll let you know after I take out the spacer this evening. I'll also report if any codes are present...

-James.

[jamesgood72]

I've been driving the car for a week now, and still have idle speed problems. A little searching on here found this thread by Loren :

http://www.renntech.org/forums/index.php?showtopic=6828

I would think that it's that idle speed control that is not working correctly, or not connected properly. I will check that out tonight. Would there be any codes I should be able to read if that were the case?

Thanks,

-James.

[jamesgood72]

I still have this problem in my car... :(

I disconnected the idle speed control (the 4 contact connector on the bottom) and started the car, and the car ran the same as when it was connected. Can anyone confirm if that is to be expected or not? I think maybe the solenoid in the control is not opening the intake; does that sound right? How much does a new one cost, roughly? I will attempt to clean this one out and see if I can get it to work.

Thanks for any insight...

-James.

[jamesgood72]

Well, I finally have this fixed. It was the Idle Control Valve (ICV), which was all coked up. I removed it from the throttle body (after removing the throttle body from the engine first), and cleaned it with carb cleaner, a toothbush and finally some cotton buds. Put it all back together, and the idle is now perfect, settling out at 800 rpm after a second or so.

This post helped me : http://www.renntech.org/forums/index.php?s...c=9299&st=0

I have pictures of the process if anyone is interested.

-James.