Idle problem with 3.6 engine
 

I have a problem with the idle on my 993 Euro Vario '97 engine.

Once the car warms up the idle is too high. Around 1200 RPM.

I have a light flywheel and Cintex chip (provided with Timmins kit). following Bill's Verburg recommendation on other posts, I tried to adjust idle with the ISV. The problem is that if I adjust the ISV to idle at 900RPM when the engine is warm. It won't start when cold.

I also read on other threads that it could be a problem with a loss of vacuum. I connected a vacuum gauge to the system and got 15cmHq (steady) when idling. Is this ok?

Any other suggestion?

Thanks in advance

You might try looking for intake leaks

Thanks Bill

How do I do that? Where should I look? Sorry but noe idea where to start!

Smoke-look for a stream, ether- look for increased idle speed

Sorry, Bill I am slow today... but could you give more details.

You mean to shoot smoke around the intake and then look for the stream. If so, what do you use to produce smoke?

don't use carb cleaner, but buy some brake cleaner and pray around your intake area and listen for the sound of the engine rpm increasing...that would indicate a leak. brake cleaner is more volatile then air, so you'd expect an increase.
ryan

actually, i have an intake leak on my 964..i can hear the hiss, but i'm actually new to the 964 and having my troubles isolating it. anyone have suggestions as tot he most common sources of intake leaks on these cars?

Maybe your chip is faulty....

I will try the intake and if not I will insist with Timmins to get an exchange. I suggested a while a ago that it could be a problem with the chip but he was not very keen to exchange it.

Initially, I thought it could be the ISV, but not... I am running out of options. Car is running great otherwise but the idle issue is quite anoying.

High idle could be the microswitch at the throttle body. Hunting idle is indication of a vacuum leak.

Is the microswitch accesible? any pics of where it is located and how it looks like? What could be the problem with it?

Thanks a lot for your help

I would start over looking for vacuum leaks. You dont need any smoke or cleaner to find many leak. I am in the same process right now. When you have just a few small leaks you can adjust the idle where you want it either hot or cold but then the ISV can't overcome the changes either way. So if you screw adjuster in to far the car won't idle when cold if too far out the idle hunts.

I don't have pictures but...

hose adapter from PVC valve to oil tank. (crack)

Hose adapter from brass to plastic fitting on brake booster.

little plastic hoses come loose from fuel pressure regulators

Cracking on the intake boot itself or loose connections to the intake boot

Check that the vacuum line is on top of the control valve just before the PVC valve.

The small loop vacuum line that goes from throttle body to thermo switch can crack.

Make sure that when adjusting the idle the car is warm and that the test port is jumpered and the 02 sensor is disconnected. That should center the ISV so it can adjust both hot and cold.

If still not working after that then start in with the brake cleaner to look for intake leaks.

Thnka dfink.

Could you please give me more details on:

"Make sure that when adjusting the idle the car is warm and that the test port is jumpered and the 02 sensor is disconnected. That should center the ISV so it can adjust both hot and cold"

Where is the test port you are refering to, on my 3.6 engine?

The microswitch is depressed by the throttle body arm when at idle. The switch could be faulty or gummed up or out of alignment.

BTW, there are many engine diagrams on CD that you can get with exploded diagrams that will help.

I looked for intake leaks with both propane and starting spray. I was not able to detect any change in idle. I sprayed it on every inteake boot, and every vacuum line I was able to see...and nothing.

I will try ti check the throthle swith, but I am not sure if I can access it with the engine on the car...no way I will t ake the engine out for this!!

It's on the trottle arm where the cable or rod pulls on the throttle body....there's a tiny "micro" switch where it rests at idle. Ya can't miss it.

I keep having trouble tracking this problem. I kind of ruled out vacuum leaks after thourough search with propane and starting fluid.

I was not able to find the microswitch though. Do you have a part number so I can check PET for where is it install?

Is this the microswitch?

Throttle Switch, 911 Carrera 2/4 (1995-98), 911 Turbo (1995-98), Each

http://forums.pelicanparts.com/uploa...1172445663.gif

Mario, I had the same problem last year. I also used Timmins Kit with Cintex Chip. The chip was faulty. Timmins offered exchange. So I sent him back the chip and installed the stock chip.
The amazing thing is that I don't have Idle problem any more with the stock chip and didn't go back to cintex chip any more.
Add. problem with Cintex chip was that the revision limiter was set up on 6100 rpm. Timmins said that was a bad lot of cintex chip.

i will try with Steve.

I do have the stock chip. So, i guess I will try to exchange it and see if it works better.Btw, what's the advantage of Cyntex chip vs stock?

Well, the Cintex Chip suppose to reduce the staling issue when you combine 915 with 3,6. at the same time it should get you up to 15 more hp. But to be honest, I didn't recognize anything, but that could be because of the faulty chip.
I will try a Steve Wong chip soon: http://www.911chips.com/
Received good feedbacks about this chip on Rennlist.

Be careful....I don't believe Steve has a chip for the Varioram motor. Perhaps that's changed?

Steve Wong or Steve Timmins?
Wong has chips for 993 Vario engines and Timmins uses Cyntex for 993 Vario as well.
Wong Chip: http://www.911chips.com/993chips.html
Timmins Cyntex Chip: http://instant-g.com/Products/36Conversion/Options.html

I just sent and email to Timmins asking him to exchange the chip. Let's see if this works.

Thanks

"I don't believe Steve has a chip for the Varioram motor"

There's NO chip for the U.S. '96-'98 993 DME ECMs.
The '96 can be Mickey Moused by soldering a "piggy-back" device,
and the '97-'98 must be flashed.

Read here: http://forums.rennlist.com/rennforums/showthread.php?t=326609

"If still not working after that then start in with the brake cleaner to look for intake leaks."

If the engine runs smoothly at the high idle, then the air leak is around the
throttle body and NOT directly into the intake manifold. An intake air leak
into the intake ports, i.e. manifold leak, will usually cause an idle misfire.

According to his homepage he has one:
96-98 Euro Version 993
$350
Euro Version V-Ram
with 55-pin DME connector
includes Bosch DME #0.261.203.678
My DME is a 96 European version with 55-pin connector, so this should work.

"My DME is a 96 European version with 55-pin connector, so this should work."

Must be located somewhere other than the U.S. or in some state where no emissions
testing exists. A late 993 engine requires OBDII testing!

Idle problem with 3.6 engine
 

Yes, I am located in Germany and OBDII was not required for Europe.

Below is a picture of the back of my engine. Could anyone point me to where the throttle switch is?

Thanks a lot

http://forums.pelicanparts.com/uploa...1173278580.jpg

MM,
993 does not have a throttle microswitch as used on 964.

993 uses a Throttle potentiometer
Here is what is used on Motroic 5.2(US OBD2)
http://forums.pelicanparts.com/uploa...1173280591.jpg

http://forums.pelicanparts.com/uploa...1173280473.jpg

RoW vram uses M2.1 which is in many respects the same

Thanks Bill.

Now, I understand why I was not able to find it :-)

I guess my last chance is that the problem is the chip. I already contacted Timmins and he will exchange the one that I have. Hope this solves the idling problem.

I'm in the process of t/p ing my RoW 55 pin RS engine into my 55 pin US '95.

Not done yet but so far it appears that the Cyntex chip was the issue.

But as I said it's not a done deal.

Another possibility is the adaptive nature of the 993 idle system.

The throttle potientiometer on the throttle shaft determines the angular position of the throttle shaft. The 0 position(idle) is determined in an adaptive process by the DME control unit.

If the battery is disconectedor the control unit has been separated from the system, the engine must be restarted w/ the throttle valve fully closed.

A self adaptive system always selects the smallest opening angle of the throttle as the idle position. If the throttle moves, the engine idle settings are swithed off, at ~66&deg the full load menu is activated,

Having a Hammer or PST2 lets you read the actual vallues that the DME is seeing from this process. Soemtimes the thrttle cable is the issue.

W/ the cable adjusted to 0 at idle, it will read 84&deg &#1773&deg at wot

Another (remotely) possible issue is the coding of the DME, there is a 2pin connector branched off from the DME wire harness, near the connector.

for RoW regulated engines this open, for RoW unregulated this is bridged w/ a 1k<FONT FACE="SYMBOL">W</FONT>, US cars have a harness to ground

bill, do you have a similar diagram by chance for the 964? having moved up from a cis 2.7 i'm trying to learn this new engine when i get time. also trying to chase down an intake leak, confirmed by spraying brake cleaner around the manifold 'area' that's giving me an idle hunt.
if you can, thanks!
ryan

I had these kinds of problems with high idle and surging idle after a service

Turns out that the motronic computer loses its brain after the battery is disconnected and you need to throw the hammer back on and have the car re-adapted. Hopefully your motronic diagnistic port is available.

I would start there.

Bill, How do I do this? Is it just a matter of not depressing the throttle the first time I start the engine after disconnecting the battery?...because I did disconnected it several times and never took any specific action when starting the car again



Unfortunately, I don't have acces to a Hammer. Nevertheless, I am in the process of building a DYI code reader for OBD1 993 engine.

Bill, I think you are also working on this on Rennlist, right?

Do you know if this reader will allow me to read the info that you are refering to.

I already connected an OBDII port to my DME, following instruction on this forum. Hopefully, once i get the reader I will be able to crack this issue.

Just start w/o touching the throttle, you are supposed to let it sit that way for up to 10min. yes, it will perform all or at least most of the functions of a hammer.

The closest I have on hand is a '95 993

the 964 is somewhat different in a few respects but mostly the same
http://forums.pelicanparts.com/uploa...1173402069.jpg
One of the differences is that a 964 does have a microswitch
http://forums.pelicanparts.com/uploa...1173402537.jpg

I had these idle probs...Steve Weiner at Rennsport hooked me up with a new box and my troubles were over....

Wasn't cheap but nothing is when you live on the edge.....

Steve is THE man. Always will be in my book.

thanks for remembering me, bill..knew you'd come around! SmileWavy i'll save the images.