Is this true "idle surge"..or something else?

[93TSI_370K]

Sorry, this may be a broken record…for seeing this the millionth time.....

Question: After reading a bunch of articles on idle surge and a ton of postings, I am wonder if I have true “idle surge” (as loosely defined) or is it something else???

Immediately when I start the car the idle is stable but after about a minute the idle is about 1500 rpm and then it just drops like the injectors cut off and then at about 1000 rpm's the rpm’s pick up again to about 1500 rpm and then it drops again. It repeats this pattern but gradually as the engine heats up, the frequency of it gets slower until finally as it gets to operating temperature, it stops and the idle stabilizes!!!!!! (the tach I am watching is the stock tach in the dash)

The ISC is relatively new, a year maybe two years old, I’ve checked the coils on it and they are not open, the TPS is correctly set, I just replaced the intake manifold gasket, the injector insulator seals (that go in the head as the old ones were hard.) The throttle body was cleaned, I replaced the o-rings on the throttle plate shaft.

Question: If it was a vacuum leak, when it reached operating temperature, it would not clear up and it would continue to do this, wouldn't it???

Also, the CEL is not burned out….and does not give a code, so maybe I should take my own advice I have given and eliminate all the components that would give a CEL and concentrate on everything else.

I appreciate anyone’s input on this.

 

[Travisgsx96]

Sounds like true idle surge most likely Isc pull it and use an ohm meter to check between 1-2 3-4 and 5-6 should give strait reading across. And yes if it was a vacuum issue it shouldn't stop at operating temp

 

[Bud92gsx]

Mine only surges when in park at operating temp.Vac delete here I come.

 

[viridionplague]

sounds to me like your BISS to far open

http://www.vfaq.com/mods/BISS-1G.html

also the idle surge portion

http://www.dsm.org/how-tos/tttt/tttt3.html

 

[93TSI_370K]

Travisgsx96, I was 99.99% sure my ISC was fine, so I double checked the ISC coils, 31.6 to 32.3 ohms, they are fine. Thanks for werifying that a vacuum leak will not go away when the engine reaches operating temperature, I did not think that a vacuum leak would disappear..unless the FIAV valve gasket between the TB and the FIAV is leaking and when that heats up, the metal will expand and seal better. I have had stranger things happen to my cars, that when I tell the story to professional mechanics, they just shake their heads in dis-belief.

Or I could add a FIAV block off plate and see if that makes a difference....that would eliminate the ISC and FIAV as a problem....hmmmm

Will try some other things this weekend and post back.

Does anyone know where information can be found how chronologically the ECU functions from cold strart to operating temperature or how the ECU processes the inputs and the resulting outputs? I doubt anyone has deciphered the lines of code or even be able to view it, but it is worth asking.

 

[93TSI_370K]

Okay, completely stock TSI. Trying to fix so I did the boost leak test and set the crank at 40 degrees before TDC. I found a couple small leaks on the fitting for the air bypass hose on the air hose from the air cleaner to the turbo. Used some RTV on those small leaks. But still not holding even 10PSI. I could hear air leaking but it was kind of hard to locate so I used the hose in the ear method and it sounded like it is leaking at the head where the injectors go. So I sprayed soft soap/water around the base of the injectors and it definately is leaking on all four injectors. [Background... I had my injectors sent out to get them cleaned, filters changed at an injector service that uses an ASNU injector machine.] When I re-installed the injectors I used brand new injector insulators but I did notice that even after I had the fuel rail torqued to 7-9 lb/ft, I could rotate the injectors with my fingers. I thought that was kind of funny but then I really never checked if I could rotate them with the old hard insulators before I removed then to send them out for service.

So, what am I doing wrong? Sould the injectors be compressed to a point (after the fuel rail is torqued) so that I cannot rotate them pushing with one finger? Any suggestions?

I was thinking that maybe I could find some silicone "O" rings (for the higher temperature) and put them between the pintel cap and the insulators to take up more space when I put them back in?

Thanks