87 3.2 idle issues

[Jimintampa]

Gentlemen,
I have a 1987 3.2 with 97,000 miles, engine is in good shape as in compression etc. I just installed a new idle control valve last week as I was having periodic issues of severe rolling idle up to and including stalling, if I clean the valve reinstalled it sometimes it wouldn't do it again for weeks, finally I bought the 180 dollar valve along with new brake pads etc sort of a spring tlc kinda deal.
I installed the valve examining the wires and rubber hoses which all appear to be OK, drove the car about 100 miles it ran perfect ... I was thrilled. Got in this morning after it warmed up a little bit it started doing it again , very disappointing, I seriously doubt that the new valve can be bad too manifesting the exact same conditions as the old one. Does anybody here have any idea of what this could be, I am hoping there may be another component I am not familiar with that might be the culprit as if its a wire issue that only loses connectivity intermittently I may never find it... Thanks in advance, Jim

[techman1]

Jim,

The valve adjusts the idle up and down, based on signal from motronic. On a properly set baseline, it really does not have to move much. I was told there is an issue when the idle baseline was way off, meaning either too high or too low.

Look for the procedure to set the base idle for your car. This involves using a jumper to take the ICV out of the loop, and then adjust the idle. Over working the ICV valve is not good.

That all being said, I recall another user who knows this dme inside and out warn about an item inside the box which can overheat and need replacing, and it affects the idle circuit.

[stlrj]

Base mixture too rich and base idle too high.

Problem is, no one knows how to make these basic adjustments anymore and are only trained to replace parts.

[dion914-6]

I'm chasing down some idle issues on an 86 3.2 right now. Do a simple search on this forum. You will find days of reading material, and many more things that could be causing the issue than just the ICV.

First step, have you checked for any vacuum leaks?

[Jimintampa]

lol I know I read some of them wow many many different possibilities, the base line idle I doubt as it runs perfect sometimes, for long periods of time, many successful cycles of start /run/off then without rhyme or reason as in hot or cold it starts searching for idle, suddenly not gradually.
after I wrote the first question this morning I did search the forums and found everything form burnt valves to blown head gaskets...none of these are likely as like being pregnant either you are or you aint no such thing as a little bit pregnant, valve issues would manifest everytime, head gasket etc. One interesting thing was the oil cap? wow I really didn't understand that one but for giggles I loosened it took a 25 mile drive run it thru the gears 3/4 throttle to 4 grand, pulls cleanly and crisply no blubbering like rich mixture no backfiring on decel like lean mixture, I lugged the engine down ( I really cringed I hate doing that) but at almost any gear and speed it never protested just pulled cleanly, idle was smooth and rock steady thru it all.
A vacuum leak is a possibility I suppose but I cant find it, did the old wd40 trick no change in idle just a mess. It seems to me that something like a wire or another component that I am unaware of is intermittently giving me grief, I am not delusional enough yet to think my oil tank is the culprit. thanks for the feedback I will keep checking back, there are lots of Porsche savvy guys on here that for sure know more than me.

[Nine9six]

Do a search for "surging idle" or "hunting idle"
The issue could be from any number of causes, such as a bad o2 sensor, warm up regulator (wur), intake air leaks, to malfunctioning ICV...

[dshepp806]

"rolling idle"? mm..I'd certainly verify that the idle switch is dead on, at minimum....

As Nine9six indicated (and search-suggested) , it can be several things,..(and it looks like it's not gonna' be the ICV!)

Best,

Doyle

[Jonny042]

Originally Posted by Jimintampa

One interesting thing was the oil cap? wow I really didn't understand that one but for giggles I loosened it took a 25 mile drive run it thru the gears 3/4 throttle to 4 grand, pulls cleanly and crisply no blubbering like rich mixture no backfiring on decel like lean mixture, I lugged the engine down ( I really cringed I hate doing that) but at almost any gear and speed it never protested just pulled cleanly, idle was smooth and rock steady thru it all.

You're saying it runs much better with the oil cap loose?? I thought that would cause a massive vac leak. I will have to do some searching on this.

I have a mystery surging idle but more of a misfire or mixture problem.

[dion914-6]

I was thinking to myself today. Here I am driving my 2006 VW Jetta Tdi with 105K miles on the clock, and have never, ever had an issue with it. It still idles and runs like the day I bought it.

On the other hand, I've spent the better part of the last year putting up with, and tracking down idle issues on a 77K mile 3.2 Porsche engine......

Something is not right.

Dion

[ischmitz]

why not keep driving the Jetta and sell the 911........

[dion914-6]

That's why the Jetta is an everyday driver, and the 3.2 is the toy. Besides, it's in a better chassis, a 914-6.

[Tspringer]

Originally Posted by dion914-6

I was thinking to myself today. Here I am driving my 2006 VW Jetta Tdi with 105K miles on the clock, and have never, ever had an issue with it. It still idles and runs like the day I bought it.

On the other hand, I've spent the better part of the last year putting up with, and tracking down idle issues on a 77K mile 3.2 Porsche engine......

Something is not right.

Dion

The something that is not right is the simple fact that the 3.2L Porsche engines injection systems are junk. The sheer volume of idle and poor running issues posted on every P-car forum out there and the clear ongoing inability to correct this for a huge chunk of those experiencing these problems spells this fact out crystal clear.

My '73 911T has a '86 Euro 3.2L in it. The idle hunts terribly, has since I got it and so far nothing I have tried corrects it.

IF I remove the oil tank cap.... idles great. Oil tank cap on, idle hunts and surges horribly and engine dies.

My question is starting to be less about how to fix this and more about how to junk the entire POS Porsche injection system and replace it with something else that CAN be diagnosed and fixed!

[DRACO A5OG]

Oh Terry, don't let it beat you Brother. Check your OP.

[Jimintampa]

Originally Posted by Nine9six

Do a search for "surging idle" or "hunting idle"
The issue could be from any number of causes, such as a bad o2 sensor, warm up regulator (wur), intake air leaks, to malfunctioning ICV...

thanks nine6 I have looked at the o2 sensor looks ok never heard of a warm up regulator, more research, like I said earlier already did the WD40 spray deal no change in idle so intake leak seems unlikely. thanks again.

[Tippy]

As someone told me that is common sense, do all of the diagnosing at the plug going into the ECU (or DME for other's liking).

A sensor can be within range (when testing by itself) but the harness going to the ECU can have a bad contact, damage, etc., interupting data to the ECU.

Test all of the voltages/ohms at that plug and it should get you to the root cause pretty quick.


GL, I am praying my idle control switch (microswitch on the backside of the TB) cures my surging/bucking and sometimes backfire issue.

[Jonny042]

Originally Posted by Tippy

As someone told me that is common sense, do all of the diagnosing at the plug going into the ECU (or DME for other's liking).

A sensor can be within range (when testing by itself) but the harness going to the ECU can have a bad contact, damage, etc., interupting data to the ECU.

Test all of the voltages/ohms at that plug and it should get you to the root cause pretty quick.


GL, I am praying my idle control switch (microswitch on the backside of the TB) cures my surging/bucking and sometimes backfire issue.

Is it easy enough to back-probe this connector to do voltage checks? I haven't looked at it with this in mind but would be handy.

I have an analog dual range (0-5, 0-12) 180 sweep voltmeter for doing this sort of thing. You can hook it up and drive it around and see what is happening.

[Jonny042]

Originally Posted by dion914-6

I was thinking to myself today. Here I am driving my 2006 VW Jetta Tdi with 105K miles on the clock, and have never, ever had an issue with it. It still idles and runs like the day I bought it.

On the other hand, I've spent the better part of the last year putting up with, and tracking down idle issues on a 77K mile 3.2 Porsche engine......

Something is not right.

Dion

Well there you have it's (collectively) our own damn fault.

Take a look at state of the art computers at the time, 1987..... and compare that to 2006.

Then realize it's a miracle that the car runs at all!!!!! Or that you can buy parts!

[db_cooper]

Most of the idle and running issues are not related to poor design..it is due to 20 year old components. 90% of the problems are air leaks. Making sure the intake is sealed with no bad hoses or failed intake gaskets is a good place to start. Use any method you want to make sure the intake is not leaking.

A big percentage of the 3.2s have had..somewhere in the past..the air flow meters opened and fiddled with. Check and see is the AFM cover has been removed and resealed. If the AFM is out of calibration or simply worn..your idle may suffer.

Check all the grounds..remove and clean them all. After all..its been a long time since its been done.

Fuel pressure needs to be checked too..the pressure regulator is probably original. They last a long time. Don't count on them still being in spec.

Don't forget your fuel injectors... a fine spray pattern and consistent fuel volume for all six will make a big difference.

Put an Ohm meter on the throttle switch and confirm the idle and WFO contacts are working. Just because it clicks when you work the throttle doesn't mean there is good low resistance contact in the switch. Remember..these things are old enough to vote now.

A good CO meter connected upstream from the cat..insure your base CO is correct. Too rich or lean..you will never get a good idle.

And..once all this has been done..you may still have some idle wandering when cold for the first 5 seconds. They did that when new from time to time too.

A more modern software package (EPA Paranoid 2.1 from Porsche is the base software) for the DME will address that..see our host for upgrades from Steve Wong.

[Tippy]

Originally Posted by Jonny042

Is it easy enough to back-probe this connector to do voltage checks? I haven't looked at it with this in mind but would be handy.

I have an analog dual range (0-5, 0-12) 180 sweep voltmeter for doing this sort of thing. You can hook it up and drive it around and see what is happening.

Maybe, but it is so easy to pull the DME harness plug and test right there where it counts most.

[Jonny042]

Originally Posted by Tippy

Maybe, but it is so easy to pull the DME harness plug and test right there where it counts most.

That is easy, yes, but I was thinking of having a "real time" voltage reading while running/driving.... especially of things like the IAT, TPS, etc and especially the AFM to see if there are any flat spots, and the O2 sensor (ensuring that the heater cct is working, too...).

There aren't that many pins. If you could systematically check them all, while the car is running/driving, you could eliminate the electrical stuff and get on with checking for leaks.