car stalling

[TSI Fanatic]

Alright so i own a 91 talon tsi awd i went out for a tour with the lads last night started the car up idles at around 1800-1900 rpm then once it got to operating temperature it idles at 750. so we drove up to a neighbouring city approximatly 45mins away, got to the parking lot shut the car off went in to the local pizza pizza for a slice came back out started the car ran for about 3 seconds then stalled. started it again and the exact same thing happened so i started it again and kept my foot on the throttle for a few seconds to clear it out but it still stalled. tried twice more before it finally stayed running but would only idle at like 550 rpm and would actually surge down to about 450 and almost stall out. We stopped at another store came back out and it was doing the same thing but this time it would not stay running just kept starting and stalling instantly. so i kept my foot on the throttle to keep it going to get down the road but every time id let off while driving it would want to stall. I let the car sit for 2 hours in the lot let everything cool down and it started fine and ran fine idling at 750, this problem only seems to happen when the car is at operating temp for a certain time.

 

[k69ss]

This sounds similar to something I helped a friend out with a little while ago. He was going to sell his 2000 Audi S4 because it would not idle at operating temp... he replaced the MAF sensor and checked all the vacuum lines which all turned out to be fine so I told him to replace his o2 sensors and after that the car ran fine... I know he had an Audi but the concept is the same.

 

[Dhan]

When this happened to my n/t, it turned out to be an electrical problem. Double check all grounds and reset your ECU. This fixed my problem.

 

[fmxInsane]

Its happening the exact thing to my talon....

 

[TSI Fanatic]

ok ill be checking grounds and resetting the ecu shortly. Now on the possibility of it being the maf i do have an hks maf unit installed on the car, would this be causing any problems, like the ecu getting confused signal wise at certain temps?

 

[k69ss]

I don't think its your MAF, I was saying your o2 sensor.. once your car reaches running temp the atomization of your fuel is better, meaning that its going to burn more efficiently than when your engine is cold, which also means your o2 sensor should read higher oxygen levels in your exhaust telling your ECU to add more fuel to the combustion chamber... BUT, if your o2 sensor doesn't read a higher oxygen level it wont add more fuel to the mixture and your engine will starve for fuel... creating stalling or rough idle... if it were a grounding problem your car would run like shit from the moment you started your car.

 

[shay4g63]

check your 02 voltage. easy start and elimination.

 

[Dhan]

Just checking voltage of the O2 using the methods described in the shop manual doesn't always work. I did the tests and found the initial heating wire and the sensor were working perfect, but then Link reported that the O2 was not oscillating as it should. Turned out the O2 was bad (had been fouled by oil) despite it passing the tests. You may not have Link, but just an FYI.

 

[steve]

Check the ISC and once it and the ECU are verified to be working reset your BISS.

 

[k69ss]

I agree with Kreez on this one, you might be able to check the voltage and rule out an o2 sensor sometimes when they are older however, this happened almost instantly and like Kreez said may have been fouled by oil or some other contaminate. So yeah, check the voltage would be my first step since its the easiest but, I would not stop there if it passed that test.