AC idle drop, sometimes stalls

[PLP]

I hate the search function...

How to search for AC and idle drop?
Two letters are ignored or I am not finding anything at all.

I bet the question was covered a few times.

So here it goes.
2003, 2,7, 5 sped MT.
The way the car behaves - when I am driving (no AC), it seems to be generally fine. Sometimes the idle drops a bit lower, but recovers. Situation like this: going in 3rd gear or so, rpm maybe about 2000, coasting, 1200. Depress the clutch, idle drops below 800 (like 500) and recovers to 800 more or less. Steady from there.

With AC - if I was to repeat it, sometimes it would drop to 400 or lower and from time to time it does not recover, i.e. stalls, dies.

From what I read it might be ICV, but is it?
What else?
No other problems - starts fine, power is there. Rather smooth power delivery.
Filters, sparks, coils - all less than 10 k miles.
AC blows cold, like cold enough to make it comfortable cold.

[JFP in PA]

The DME controls the idle speed by sending a signal to the idle control valve, telling it to increase the idle speed slightly until the compressor turns off. I would start by looking at the wiring going to the valve, and if nothing is found, replace the valve.

[blue62]

From you description it sorta kinda sounds like you could maybe have a vacuum leak.
Take a good long look around your engine bay and or do a simple vacuum test on it.
A simple vacuum gauge is pretty cheap.

[wiebuschk]

I am thinking vacuum leak also. Smoke test or gently spray some starting fluid around hoses and under intakes. If there is a leak the motor will speed up.

[PLP]

Thanks guys.
I will start with easy starter spray then to move onto the vacuum leak check and if that is fine, replace the ICV.

Speaking of which - I read it already here, and confirmed with my recent findings, the OEM one is around 450-600 USD. Some other brands are as low as 20 USD.... any reason why to get 30 cheap ones vs one expensive?

Deutsche parts has one for 150 or so.

And one more thing.

Is Durametric/any programming needed for the new ICV?

[JFP in PA]

Bosch makes the Porsche part, which is well made and durable; I have no idea of the quality of the $10 knockoffs.

No programming is required.

[PLP]

0280140572

Not available anywhere...

OK, I will check and then come up with a resolution.

[JFP in PA]

Bosch may have an exclusive deal with Porsche because the version Porsche uses internal electrical values coincide with the electrical values the DME is expecting. One thing you need to recognize is that some of the aftermarket units may not be the same electrically, just physically, which could endanger the DME as they were designed for a different application. You need to decide if the cost savings are worth the risk................

[PLP]

I completely understand what you are saying and I would be just fine with a 200 USD part, which is already in itself a lot.
But over 600 for ICV? C'mon Porsche...

Anyway, let's start with small steps and tests first before I start dumping money.

[78F350]

Originally Posted by PLP

I completely understand what you are saying and I would be just fine with a 200 USD part, which is already in itself a lot.
But over 600 for ICV? C'mon Porsche...

Anyway, let's start with small steps and tests first before I start dumping money.

I'll bet there are a few of us that can send you a used original Porsche one for a reasonable price. I'd try a throttle body cleaning too before buying parts.

[PLP]

Originally Posted by 78F350

I'll bet there are a few of us that can send you a used original Porsche one for a reasonable price. I'd try a throttle body cleaning too before buying parts.

How long would a used one last?

Is there anything else that may cause the unstable idle?

[JFP in PA]

Originally Posted by PLP

How long would a used one last?

Is there anything else that may cause the unstable idle?

How high is up? How far is long? There is no way of knowing.

If you have a friend with a similar Boxster, try swapping ICV's and see if the problem moves with the valve................

[blue62]

Originally Posted by PLP

How long would a used one last?

Is there anything else that may cause the unstable idle?

The three things that I can think of off the top of my head are.

Vacuum leak.
Faulty MAF sensor... or related wiring
Faulty ICV.... or related wiring

I am sure there are more things:

[PLP]

Originally Posted by blue62

The three things that I can think of off the top of my head are.

Vacuum leak.
Faulty MAF sensor... or related wiring
Faulty ICV.... or related wiring

I am sure there are more things:

Sure, many things could be a problem, but if the car starts just fine, has the power, runs smoothly, and only has idle issues, especially at AC load, then what could that narrow down to?

Again, if I let the RPM drop quickly, then it has tendency to stall. If I do it gently (engine braking down to close to idle) it will dive, but recovers and stays OK.

[blue62]

Originally Posted by PLP

Sure, many things could be a problem, but if the car starts just fine, has the power, runs smoothly, and only has idle issues, especially at AC load, then what could that narrow down to?

Again, if I let the RPM drop quickly, then it has tendency to stall. If I do it gently (engine braking down to close to idle) it will dive, but recovers and stays OK.

The three things I listed is where I would start.

[PLP]

Originally Posted by blue62

The three things I listed is where I would start.

Yup, I will get to it. Does not seem to be pressing issue... I rather need to take care of my daily and tire low pressure

Anyway, why I asked was due to the fact that I experience issues at idle under load. If I do not see (or I am just believing I do not...) issues elsewhere, I was trying to justify MAF issues and related. If the MAF was filthy, clogged, wouldn't it exhibit problems elsewhere?

Vacuum leak - under load/higher rpm, small leak would not be noticeable, so this one makes sense as well.

ICV - it's responsibility is idle only.


Just "brainstorming".

[wiebuschk]

FWIW my ICV was in question. I installed a $20 ebay one to troubleshoot with and have not taken it out. It works fine.

[blue62]

Originally Posted by PLP

Yup, I will get to it. Does not seem to be pressing issue... I rather need to take care of my daily and tire low pressure

Anyway, why I asked was due to the fact that I experience issues at idle under load. If I do not see (or I am just believing I do not...) issues elsewhere, I was trying to justify MAF issues and related. If the MAF was filthy, clogged, wouldn't it exhibit problems elsewhere?

Vacuum leak - under load/higher rpm, small leak would not be noticeable, so this one makes sense as well.

ICV - it's responsibility is idle only.


Just "brainstorming".

Old and very wise rule of automotive trouble shooting:
Always go with the simplest things first.
Then work your way up the diagnostic tree.
So.....
Vacuum test is the simplest of the three in my list you just need a vacuum gauge.
MAF sensor is next.... you can unplug it then take the car for a drive and see if the issue changes.
Wiring can be tested with a Multi Meter.
Last replace the ICV..
Simple.

[PLP]

Originally Posted by blue62

Old and very wise rule of automotive trouble shooting:
Always go with the simplest things first.
Simple.

Very so true. Start with outside and follow inside.
My old story - I was helping my dad to resolve why in his 1982 Passat front parking lights would not work. It just came back from a body shop and both headlights were replaced. Low beams, high beams, fogs - are good. Parking lights - gone. Rear works, though.
Those cars were known for electrical issues. The old style connectors were poor.
I spent 3 hours chasing fuses, relays, connectors. I found that power is delivered to the headlight.
So finally, lets check the light bulbs.
Well, they were never installed.... and once you put them in - all worked just fine.
I spent 3.5 hours doing a 15 minute job. In late fall, in Poland (kind of like Michigan weather...).

Originally Posted by blue62

MAF sensor is next.... you can unplug it then take the car for a drive and see if the issue changes.
Wiring can be tested with a Multi Meter.

So you can just unplug it and drive? It will not scream at me?

[blue62]

Originally Posted by PLP

Very so true. Start with outside and follow inside.
My old story - I was helping my dad to resolve why in his 1982 Passat front parking lights would not work. It just came back from a body shop and both headlights were replaced. Low beams, high beams, fogs - are good. Parking lights - gone. Rear works, though.
Those cars were known for electrical issues. The old style connectors were poor.
I spent 3 hours chasing fuses, relays, connectors. I found that power is delivered to the headlight.
So finally, lets check the light bulbs.
Well, they were never installed.... and once you put them in - all worked just fine.
I spent 3.5 hours doing a 15 minute job. In late fall, in Poland (kind of like Michigan weather...).




So you can just unplug it and drive? It will not scream at me?

It will most likely through a code for the MAF.
But you can just delete it.
When you unplug the MAF the DME reverts to a default fueling strategy as a work around.
So you can use that fact to check MAF funtion.
Your just looking for any change to the issue your having..so unplug it go for short drive turn on the AC and evalute the results.
Then plug the MAF back in and clear the code if any.