Idle prob just won't go away! - Page 2

Porsche_monkey · 06-19-2007, 12:04 PM

The high idle won't occur if the set-up is wrong. It takes two minutes to check, and you really should start there. At least reach in and make sure you can hear the switch operate as the throttle opens.

Maybe try driving with the ICV jumpered. That way you can set a steady idle, and it should stay there once the car is warm. That should rule the ICV out.

84porsche9113.2 · 06-19-2007, 12:05 PM

Just out of curiosity, could someone explain how the ICV works? I've never really understood that. All I know is the ICV motor can vibrate to let in more or less air. But I don't know under what conditions the motor would let in more or less air? In other words, when the ICV decides to let in more or less air, what is the DME looking at in order to decide on making these adjustments to the ICV speed? Is it looking at the rpm's and trying to let in more or less air to increase rpms, or a/f ratio? In other words what are the operating characteristics of the engine which makes it necessary to have the ICV to control idle?

This may not help fix my problem since it seems like the ICV might not be the problem, but I'm curious anyway....

84porsche9113.2 · 06-19-2007, 12:09 PM

PBH, if you read my reply to Ned above, you would know I've already done this which is again, why I don't think the idle switch is the issue here....

"I've also already made sure that the idle switch is making contact before the throttle valve opens after a specified dead travel of 1mm (per factory specs), so I'm sure it is not the idle switch either."

I've already ruled out the ICV in my mind. The fact that the ICV works fine when it first starts and when it is hot seems to indicate it is working properly. On the other hand you guys are saying it is not normal to have low idle with the screw backed all the way out and the ICV blocked off, so I think my focus should be on why that his happening, not on the ICV....

Porsche_monkey · 06-19-2007, 12:22 PM

But that wire could be broken, and a car set up without this switch will have wild idle fluctuations, believe me I know. It takes two minutes with a multi-meter. I just hate to jump past a simple test and assume that it is okay.

84porsche9113.2 · 06-19-2007, 12:30 PM

PBH, well I'm a licensed electrician (among other things) and I don't think it is the switch (and I have a very good meter too).

I know for a fact the switch does work (I've pushed in the switch and saw the idle increase by 500 rpms). If you have a light switch and you turn it on and the light works, there's no need to test it for continuity with a meter. I don't think it is any different with this idle switch. It has been demonstrated to be working very recently (like turning on a light).

If the wire was broken, the switch wouldn't work at all, and idle would not increase when releasing it, plain and simple...

84porsche9113.2 · 06-19-2007, 12:40 PM

Meant to say that I've pushed the throttle linkage till the switch released and saw the idle increase by 500 rpms when the switch was released... So I know the switch works.

From my basic understanding of what the idle switch does, the symptoms it exhibits is not characteristic of the problems I am encountering so I don't think it is relevant. I know you have good intentions in saying I should do the procedure, but everything seems to point to something other than the ICV and/or idle switch.... I may not have done the tests to rule it out but the symptoms themselves give me indications.

If you were a doctor you wouldn't test someone for strep throat when they are exhibiting sy

84porsche9113.2 · 06-19-2007, 12:41 PM

... If you were a doctor you wouldn't test someone for strep throat when they are exhibiting symptoms of an ulcer. It's no different in tihs case, I think... It might be simple to test for strep, by why waste the time?

Porsche_monkey · 06-19-2007, 12:42 PM

First you said this:

Quote:

Originally posted by 84porsche9113.2
Ned, I forgot to mention and explain -- the reason I don't think it is the idle switch is because when I blip the throttle, the idle is temporarily stable at 850 rpm for 5-10 seconds before dropping down to 500 rpms. I believe that if this was a switch issue and the switch was not making contact at idle, the rpm's would be about 500 rpm's higher than normal idle. But this is not the case.

This is completely wrong, and illogical, so I questioned it. Sorry to doubt you.

Then you said this:

Quote:

Originally posted by 84porsche9113.2
PBH, well I'm a licensed electrician (among other things) and I don't think it is the switch (and I have a very good meter too).

I know for a fact the switch does work (I've pushed in the switch and saw the idle increase by 500 rpms). If you have a light switch and you turn it on and the light works, there's no need to test it for continuity with a meter. I don't think it is any different with this idle switch. It has been demonstrated to be working very recently (like turning on a light).

If the wire was broken, the switch wouldn't work at all, and idle would not increase when releasing it, plain and simple...

Which actually makes more sense, and would have prevented some of my suggestions had you posted that earlier. But since you're an electrician, as an elelctrical engineer I will defer to your superior knowledge and stop trying to help. Sorry for wasting your time.

84porsche9113.2 · 06-19-2007, 12:49 PM

"But since you're an electrician, as an elelctrical engineer I will defer to your superior knowledge and stop trying to help. Sorry for wasting your time."

Now was that really necessary? I didnt' mean to hurt your feelings. Since you mentioned you are an electrical engineer, I guess I should mention that I took some electrical engineering classes in my undergraduate before switching majors and before becoming a licensed attorney at law. And my father is a licensed professional engineer as well as an electrical engineer and my brother is an electrical engineer. So if I needed advice on electrical engineering I'm in good company and you don't have to try to belittle me with your impressive credentials.

Anyway, again, I'd just like to get back to trying to solve the problem without the personal insults and negativity here....

84porsche9113.2 · 06-19-2007, 12:56 PM

"I will defer to your superior knowledge and stop trying to help. Sorry for wasting your time."

Did I indicate I didn't want anyone's help?? Although I do know what I know about electrical and other stuff I know and am confident in those things, I also know I am NOT all-knoweldgeable about porsches, which is why I posted and asked for advice, in the first place...

I would suggest that people (esp. PBH) not try to take things too personally here. I try not to take things personally and just call things as I see it. There's really no need for insults or belittling of others on thie forum. I am just being honest about what I know and what I think about the problem....

If anyone has any further suggestions regarding whey the idle is low even with the idle screw backed all the way out and ICV blocked off, I would appreciate hearing from them...

Thanks in advance...

Ned nyna 11 · 06-19-2007, 01:10 PM

84, we are trying to help. I said to plug the ICV because I don't know if its passing air somehow. Plugging it gets it out of the equation.

So you cannot get the idle up using the idle adjusting screw, That likely means that the orifice is somehow plugged up. You must figure out how to assure its open.

All the air after the AFM is metered, that is it has passed the AFM flap.

You should get Bentley.

84porsche9113.2 · 06-19-2007, 01:16 PM

Ned, I have factory manuals of microfiche as well as the Haynes manuals. So far I have not found anything in there to help solve the problem, but then again, maybe I'm not looking good enough.

As I stated below I did remove the AFM and rubber boot and idle screw and clean out the orifice with carb cleaner and qtips. I CAN verify that it is not plugged up and it is open (I used a mirror as well as light to look through the orifice).

So where do I go from here if the orifice is NOT plugged up?

84porsche9113.2 · 06-19-2007, 01:46 PM

I believe that if this was a switch issue and the switch was not making contact at idle, the rpm's would be about 500 rpm's higher than normal idle. But this is not the case.

"This is completely wrong, and illogical, so I questioned it. Sorry to doubt you."

PBH, by the way, I still do not see how my statement above is illogical. If you let off the throttle and the switch is not properly set, it will not make contact at idle. If the swtich does not make contact at idle, then the rpm's would be 500 higher at idle (approximately 1200 rpm's) as even the procedure you submitted states.

I suppose if the switch was bad the effect would be the same (no continuity in all positions) and the idle would also be high by 500 rpms at idle. In other words I believe a bad or improperly set switch would mainfest itself as having a high idle (by about 500 rpms) and if that is not happening, it is in all likelhood not a idle switch issue.

I fail to understand how what I said was "completley illogical"??? Again, even the procedure you submitted states the same thing.

ninelevenick · 06-19-2007, 01:46 PM

I know that I am sort of high jacking this thread, but this idle problem is just like mine; however my car is a '79 with CIS. I have good starting idle, but then 1-2 minutes later it drops to around 500 or less. Just like your car, 84Porsche9113.2, the idle will climb up to a steady 950 RPM after the engine reaches operating temp. Is there a commonality between the Motronic and CIS systems that can cause such a symptom?

84porsche9113.2 · 06-19-2007, 01:59 PM

Snipernick, you can hijack this thread anytime... The more the merrier.

Actually as stated before my idle is not as low as 500, I may have misstated. It's probably more like 600 or 650 but it doesn't sound that nice, which is why I'm irritated.

Ned has had some really good advice and suggestions so far. I'm hoping he (or others) will be able to advise where to go from here.

Unless it is a vacuum leak, I don't think there would be too much similarities since '84 was the first year of fuel injection. Ned, so you think that by going down to 100 rpms and not being able to stall the car w/ the ICV blocked off and idle screw all the way in, it might not be a vaccum leak??

Ned might know the answer to your question much better than myself. Ned?

Snippernick - I hope we'll be able to solve both our problems with the help of this forum...

84porsche9113.2 · 06-19-2007, 02:12 PM

You know i read another thread and someone had suggested replacing a coil. But I'm not really sure if the coil is dependent on temperatures like that, and I'm not willing to bite the bullet to find out because to me it sorta seems like a low probability fix.

Snipernick, if you want to try replacing your coil and letting me know if that works?? haha..

Otherwise, I hope Ned or someone else can advise us what to check next...

ninelevenick · 06-19-2007, 02:21 PM

Thank you for your generous accommodation 84porsche9113.2. Yeah, I wish I had the kind of money where I could just buy a coil to see if it solved the issue, and then give it away to a fellow Pelican if it didn't. Besides vacuum hoses aren't there more parts that EFI and CIS share? I am intrigued by this thread because it is the first one that seems to parallel my car's idle issue.

DonMo · DonMo's Garage

I have an '84 3.2. On my car, the things that effect the idle are vaccum leaks (easily checked with fuel injector cleaner at the common Carrera spot at intake gasket), sticking ICV (easy to remove and clearn, check with meter per Bentley) and last, the Motronic box (cold solder joints and bad transistors that control the ICV). I don't think it is the ICV either. I suspect it is the Motronic.

84porsche9113.2 · 06-19-2007, 04:47 PM

Snippernick, I should have said 84 is 1st year EFI. Forgive me for my ignorance -- I'm not sure how CIS works but would it be a form of mechanical injection as opposed to carburation? ('m very clueless here as to how CIS works because I don't have a CIS car and never paid attention to it).

If you have some kind of fuel injection, I wanted to tell you that a mechanic suggested I have the injectors professionally cleaned. After describing my symptoms he told me he thought it could be the injectors and that they might loosen up after getting warm. Not sure if anyone else can verify this.

I'm just trying to think of things that could be the same like the coil, injectors or vacuum leaks...

DonMo, what is your method for using injector cleaner to check for gasket intake leaks? Can you go more into detail?

I'm wondering if it could be Motornic too, but if I indeed have the same problem as Snipernick (he seems to have the exact same problem), then maybe it could possibly rule out the motronic as the likely cause...? Do you think the motronic/solder joint issue could cause the car to act in a "predictable" pattern like that and the idle works perfectly "only when hot"?

rcaradimos · 06-19-2007, 04:52 PM

Quote:

Originally posted by Ned nyna 11
84, we are trying to help. I said to plug the ICV because I don't know if its passing air somehow. Plugging it gets it out of the equation.

So you cannot get the idle up using the idle adjusting screw, That likely means that the orifice is somehow plugged up. You must figure out how to assure its open.

All the air after the AFM is metered, that is it has passed the AFM flap.

You should get Bentley.

84 When you back-out the screw it lets air in thew a tube running north to above the throttle plate. If you had carbon/crud in the hole the screw came out of I would suspect that the (tube air passage venturi) is clogged. The diameter of this passage is about 1/8" you could try carb cleaner and a stiff wire. AFM boot has to be removed. I installed an additional o-ring on screw to prevent air entering from screw area which appears that is what is happening to you, as it is backed out so much. Give that shot and let us know what you fine.
Bob