Ryan360

When I start my 964 after not driving it for about 5-7 days the idle is erratic during start (to the point where it wants to cut off). I have to put some gas to keep it from dying. But when the engine warms-up the idle is okay again. Is there something I can do to remedy this idle problem? Or is this normal after 5day storage?

Thanks!

Rocket Rob

Is it normal? No. If you start the car after it sits over night, does it do the same thing or is it only when its been sitting for multiple days?

Ryan360

It doesn't happen overnight. It only happens when sitting for days. Thx!

Ryan360

Correction: It's not as prominent on overnight start.

DaveK

Mine has started doing exactly the same thing over the past few months. I'm guessing a temp. sensor, but I haven't looked into it yet.

I got Durametric yesterday and plugged it into mine so I know it's not logged any faults. But I may see if I can monitor the temp sensors and see if they give sensible readings when I start it / warm it up.

Ryan360

Please keep me informed of your findings.
thx!
Ryan

wellcraft290

do you have a chip or LWF? also that will give you slight surging. How much variance in RPMS we talking? mine will go about 50 rpm then smooth out.

Ryan360

no chip or LWF. Slight surge only happens on overnighters, but on longer storage (5-7 days) the rpm will go about 500-700 rpm (approx) to the point where it wants to cut-out unless I press on the gas to keep it going. The 30K major service was done 2K miles ago.

wellcraft290

that is too much. what about yoru idle sensor?

Ryan360

I'm not too mechanically inclined, but can you elaborate on the "idle sensor"? What should I look for?

I also read that it could be the temp sensor and DME relay causing the problem? Could they cause the erratic idle when cold but stablize when engine is hot? (It usually takes about 2-3 mins to stabilize).

delanobe

Could be the ISV

Ryan360

Thanks delanobe! You could be on the something. This is what I found regarding ISV:

Symptoms of a faulty ISV or one that is getting progressively or intermittently faulty are:
1. Idles low or rough when cold (improving after warm-up).
2. An idle "jump" for a second or two (internal problem in ISV).
3. Erratic idling (surging) and stalling, especially when the air conditioner compressor cuts in by not compensating for the extra load. The symptoms would likely appear slowly over a period of time, but getting progressively worse.
4. A real tell-tale sign of a faulty Digifant ISV is to let your foot off the throttle pedal while running (particularly higher revs). If the rev needle drops immediately to the 500-600 range before stabilizing at 800 or so, there is a failure occurring. Sometimes the idle will drop so low that the car stalls. A correctly working ISV should drop to about 1000 or 1100 rpm when letting your foot off the gas pedal and then the needle should slowly ease down to normal idling speed (about 800).

As a general rule of thumb, if your idle oscillates over a wide rpm range (600-1400) the ISVis suspect; if it oscillates over a narrow range (800-1000), the oxygen sensor may be bad.

Ryan360

BTW, has anyone ever tried to correct a faulty ISV due to erratic idling? Thanks.

68CGPlt

Ryan I had a similar issue last year that ended up being worn distributers and rotors. I had an intermittent condition where the Idle would jump all around and the car would cut-out if I didn't correct with the addition of a dose of the gas pedal. I had previously checked and cleaned my ISV without correction to the issue. Pulling the cap and rotors is a simple process. Check for carbon deposits or significant deterioration of the contacts. Your issues could be caused by any one of the items already mentioned above, however I would check the ISV and the caps and rotors as you can do both in a matter of 30 to 40 minutes. I would also check for loose or deteriorated hoses in and around the ISV, back of air intake, etc. Good luck!

Ryan360

Thanks 68CGPlt! I'll try those first.