Idle drops after 20 secs on a 3.2?

KFC911 · 10-26-2005, 05:38 AM

I'm a bit stumped with this one. My car has developed an issue with cold starts (which may very well be my ICV) where I have to use the accelerator to keep the revs up (1600-1800 rpms) for 30 seconds or so,otherwise it will want to bog down. I've also got a consistent issue where (even when she's warmed up), at a stop light, the idle will remain steady for approx. 20 seconds, and then it wants to drop down to 5-600 rpms. After having my car down for several months, both of these symptoms appeared at the same time. That seems too coincidental, and after doing some reading, it appears that I need to check for a vacuum leak. Any others with similar experiences or advice? Thanks!

Jeff · 10-26-2005, 06:22 AM

If you suspect your ICV, You can check it with a multimeter. The resistance between the outer terminals should be 40 ohms and from the center terminal to each outer should be 20 ohms. If this checks out OK, remove the ICV and shake it back and forth. There is a plunger inside that should move freely. Use Isopropyl alcohol to clean it by pouring some in and shaking it back and forth. Repeat, let dry, re-install.

With that being said, can you give us more info on your problem? When you release the throttle do the RPMs drop to almost stalling and slowly build back up? Do they just drop and stay there? I agree you should also check for vacuum leaks. Has your idle mixture be adjusted recently?

Also the ICV test and clean is easy and should be done to give yourself a base line and to rule out that valve.

Let us know what you find.

KFC911 · 10-26-2005, 06:33 AM

Thanks Jeff, I'll check the ICV resistance(s) when I get a chance. In regards to my idle, on both cold starts and the drop after 20 secs when warm, the idle simply drops to the 5-600 range and stays there. I haven't adjusted the idle mixture since I've had the car. FWIW, I do have a Steve Wong chip installed, and she's idled perfectly since I've owned her. That is, until I let her sit on jack stands for a few months a short time back. I was doing lots of "while your're in there" stuff, and did lower the motor during the project, so that's why I'm suspicious that I've instigated a vacuum leak in the process. Thanks for the advice...I'll do some checking and report back.

mschuep · 10-26-2005, 06:57 AM

I have had some of the same problems. I cleaned the ICV like CUL8R said, no luck. I have since found this schematic and am going to check for vac leaks.

Anything else I should know while checking for vac leaks before diving in?

aj88cab · aj88cab's Garage

You might want to check your idle switch too. It is located on back driver side of the throttle body. The connector is on the front right side of the throttle body. Unplug from the wire harness and check with a ohm meter. The switch sometime needs adjusting but mine did go bad. I had similar symptoms as yours.

Good luck
Andrew

kqw · 10-26-2005, 07:35 AM

Here's another schematic:

KFC911 · 10-26-2005, 07:39 AM

Thanks for that diagram Mschuep, and for the idle switch tip Andrew (edited...and you too KQW)!

KFC911 · 10-27-2005, 04:50 AM

I followed Jeff's suggestions about checking & cleaning my ICV last night, and this morning, the cold start was just a little bit better. I'm sitting there during the 30 sec warmup thinking "well, that didn't help much". Then, on my 25 mile "back roads commute" into work, I come upon 3-4 stoplights (with wait times from 30-45 seconds), and the idle remains constant at 880 rpms

! I think I'll give her a day or so, and maybe try cleaning the ICV again. Thanks everyone!

indigowhale · 11-28-2005, 09:07 AM

Keith, any update on your idle dipping? I am having the same problem...thanks.

KFC911 · 11-28-2005, 09:40 AM

My idle issue was much improved after cleaning the ICV and continues to improve the more I drive her (after being on jack stands for a few months). When I removed the ICV, I could tell that the 'plunger' inside wasn't moving freely when I shook it, and the Isoprophyl alcohol cleansing definitely helped. I've been busy (and the idle condition is much improved) so I haven't cleaned it again yet. It may be time for a new ICV, but I'll clean it again before I go that route. Good luck!

brcorp · brcorp's Garage

Quote:

Originally posted by KC911
After having my car down for several months, both of these symptoms appeared at the same time.

Try a fresh tank of gas.

KFC911 · 11-28-2005, 10:14 AM

Quote:

Originally posted by brcorp
Try a fresh tank of gas.

Bill, this was an older thread that was revived. In my case, it wasn't an 'old gas' issue (I had my tank virtually empty while I was working on her, and promptly filled her up upon putting her back on the road). By the time I posted this thread, I had refilled at least a couple of times. Your point is very valid however...

brcorp · brcorp's Garage

Keith,

I had a similar problem, though it started after a fill-up, tried all the usual fixes (vacuum leak, ICV, CHT, etc) then I changed gas stations - problem solved.

indigowhale · 11-28-2005, 11:19 AM

Keith, thanks for the udpate. Sounds so familiar, got a problem, you seem to correct it and it creeps back later. This has been my experience with the sub-idle dip. Been though cleaning the ICV already. I think as someone with experience said, it is related to an inefficiency with the DME programming. It does seem to make sense since the behaviour is too predictable to be a failing component. You can read the Carrera Balkiness Season thread that sent me over here for more insight.

KFC911 · 11-28-2005, 02:50 PM

Thanks again Bill, I wasn't questioning your advice at all, so I hope you didn't take it wrong. Indigowhale, I read your Balkiness thread and pointed you to this one. Cleaning my ICV definitely helped, but I still have some minor issue, so that's why I think it still might be the ICV. I'd love to have one that's absolutely known to be 'good' to test my theory. I'm very much a novice when it comes to these cars, but in my case, I don't 'believe' its related to the DME. I've had one of Steve Wong's chips in my car for at least a couple of years now (and IMO, he really knows his stuff), and the idle has always been EXTREMELY stable (both cold and warm) until I put her back on the road a couple of months ago. Thanks again everyone!

brcorp · brcorp's Garage

Quote:

Originally posted by KC911
Thanks again Bill, I wasn't questioning your advice at all, so I hope you didn't take it wrong.

Keith,

No offense taken, just trying to help.

Might also check the plug wires/plugs/cap and rotor.

How long was the car sitting?

don911 · don911's Garage

I had a similar problem. The engine would cycle down rpms and then catch and gain some rpm, etc.. My issue turned out to be the connector that goes to the air meter. The connector was plugged in but one of the contacts was pushed out and not making good contact.

KFC911 · 11-28-2005, 06:11 PM

Quote:

Originally posted by brcorp
Might also check the plug wires/plugs/cap and rotor.

How long was the car sitting?

Approximately 5+ months. Started on my first valve adjustment (last winter), and one thing lead to another... I decided to have my fan/housing, etc. powder coated and sent them off to Al Reed. He did a fantastic job, but the turnaround was a loooong time. While "I was in there', I installed new NGK plugs, Magnecore 8.5 wires, a new rotor and a new distributor cap, along with some other stuff. She runs fantastic, except for the idling issue, and even that's a lot better than it was a few months ago. Don, I'll check that connector also, but in my case, the idle simply drops down (i.e. it doesn't pick back up). Like I said before, the more I keep driving her (I've driven approx 3K miles since), the better it seems to be. Thank you all for your suggestions...mucho appreciated!