PAU '94 loses idle at times

[MichailS]

Hello

Sometime when I start my 190k miles Park Avenue Ultra '94 it has no idle. I have to keep it alive with my foot for a random amount of minutes until it recovers by itself.

This only happens at startup, never all of a sudden mid-traffic. And then it runs well for months.

I have had this happen on rare occasions for 2-3 years during which I have replaced several other components, so I'm quite positive it is not the ignition module, coils, cables, sparkplugs, or a dirty MAF.

Initially it happened once per half year or so. Lately it is happening with increasing frequency to the point that it is almost daily now.

I'm guessing idle air solenoid or similar?

Any advice?

[HotZ28]

Originally Posted by MichailS

Hello

Sometime when I start my 190k miles Park Avenue Ultra '94 it has no idle.

This only happens at startup, never all of a sudden mid-traffic. And then it runs well for months.

Initially it happened once per half year or so. Lately it is happening with increasing frequency to the point that it is almost daily now.

I'm guessing idle air solenoid or similar? Any advice?

Well, if it were the idle air control (IAC) it would happen either warm, or cold! You may have an erratic coolant temperature sensor. (CTS). You can check voltage, or resistance from the sensor, however, it would be better to check this with a scanner while cold, to see if the PCM is reading the coolant temp correctly. When cold, the CTS voltage will alert the PCM that a cold start is needed and will enrich the fuel curve similar to the choke used on the cars of past generations.

[Blue Bowtie]

A stuck IAC which passes adequate air for a warm idle wouldn't necessarily pass adequate air for a cold engine, especially considering the cold enrichment. Even if the problem is the CTS or another issue, the stall saver programming (minimum RPM regardless of coolant temperature) should open teh IAC enough to keep the engine running.

While the CTS is a perfectly plausible idea, don't completely discount a dirty TB and IAC. It doesn't take a lot of varnish to completely "kill" and IAC. The upper example was completely inoperative, and after easy disassembly and cleaning, it was 100% active and responsive:

[HotZ28]

The possibility of an IAC malfunction is just another reason that you need a scanner to watch sensor functions. I agree, IAC counts are part of the equation here. A failure of the IAC may cause a low idle, high idle, or even a correct idle; however, when not functiong, idle will not change if you turn the A/C on (the idle should increases with A/C on). This is a good IAC DIY test!

[MichailS]

Hello and thanks for your interest

I forgot to mention that this doesn't necessarily happen only when the car is cold, it also happens with a warm engine. But it always happens on startup, not all of a sudden at a red light or such.

And it doesn't go away because the engine is warm. I can keep the engine alive by holding the gas for minutes, temp meter climbing to normal level, and still have it for several minutes. Then comes a point when I find that I can remove my foot from the gas pedal and it will have idle at a normal 700 rpm.

The AC makes no difference, but I noticed this autumn on a few occasions that the idle would fall and get rough when I began turning the steering wheel, only to recuperate a couple of seconds later. I haven't had that happen since.

Also, I have had the voltage drop and the car cough and tumble at cold starts a few times this autumn. That also disappeared by itself after a minute of idling.

But the "no idle" problem isn't new, I had that happen before the aforementioned issues so I'm guessing they are unrelated.

[HotZ28]

Originally Posted by MichailS

But the "no idle" problem isn't new, I had that happen before the aforementioned issues so I'm guessing they are unrelated.

Either clean, or replace the IAC and see what happens.