lets see where to begin. i have a 2002 vw gti 1.8t with 95 k miles on it, unitronic stage 1 +
sometimes on cold starts i notice that the car will sputter, only for 30 seconds if that, this has only happened on the first start up of the day, after that its fine. i've narrowed it down to
-vacuum leaks
-dirty maf
-coolant temp sensor
-bad n249 (what is the likelyhood of this?)
i initially began seeing problems when one night after heavy boost i noticed my dv (forge splitter) began fluttering, it did not do that before. i removed my n249 valve and ran a vacuum source directly from the manifold to the dv and it ran fine with no fluttering. then i cleaned my maf with rubbing alcohol and the sputtering on cold start seemed to die down. however, i reconnected the n249 valve and the fluttering on the dv returned, so maybe i have a vac leak somewhere else? i also noticed car sputtering on cold starts again (sometimes)
with regards to the coolant temp sensor, i replaced it over the summer from the black one to the green one because i had a cel for it, replaced it and the cel went away. i noticed since it began getting cold out that my temp gauge rarely reaches 190 degrees, the car does not overheat, however, so i doubt its the thermostat and the timing belt/waterpump/serpentine belt were replaced at 73k miles. could the new coolant temp sensor have gone bad?
a friend of mine scanned the car and i had 3 codes, one for n249, one for n112, and one for improper flow code. i don't want to remove these parts due to emissions. my buddy also measured my boost and i was spiking at 20-21 psi , so i've concluded that its probably not a boost leak. what we did notice, however, was that we saw boost starting at 4k rpms and not at 3 k, we think this may be because either we did the test on the vag com at one second intervals, so we think it could be a delayed reading from the vag com or maybe delayed boost because of a vacuum leak?
after this we did the same kind of test on my friends '05 audi a4 1.8t (stock) and his boost started at 3k rpms, however we did some revisions and did the test at half second intervals.
when my engine is running i notice i hear some light hissing coming from the area where the throttle body/alternator is. don't know if its just in my head or if i'm just mistaking this for my serpentine belt running.
so in a nutshelll:
- dv fluttering when connected to n249.
-temp gauge rarely reaches 190 degrees.
- possible delayed boost.
what do you guys think? thanks in advance for any help!
sometimes on cold starts i notice that the car will sputter, only for 30 seconds if that, this has only happened on the first start up of the day, after that its fine. i've narrowed it down to
-vacuum leaks
-dirty maf
-coolant temp sensor
-bad n249 (what is the likelyhood of this?)
i initially began seeing problems when one night after heavy boost i noticed my dv (forge splitter) began fluttering, it did not do that before. i removed my n249 valve and ran a vacuum source directly from the manifold to the dv and it ran fine with no fluttering. then i cleaned my maf with rubbing alcohol and the sputtering on cold start seemed to die down. however, i reconnected the n249 valve and the fluttering on the dv returned, so maybe i have a vac leak somewhere else? i also noticed car sputtering on cold starts again (sometimes)
with regards to the coolant temp sensor, i replaced it over the summer from the black one to the green one because i had a cel for it, replaced it and the cel went away. i noticed since it began getting cold out that my temp gauge rarely reaches 190 degrees, the car does not overheat, however, so i doubt its the thermostat and the timing belt/waterpump/serpentine belt were replaced at 73k miles. could the new coolant temp sensor have gone bad?
a friend of mine scanned the car and i had 3 codes, one for n249, one for n112, and one for improper flow code. i don't want to remove these parts due to emissions. my buddy also measured my boost and i was spiking at 20-21 psi , so i've concluded that its probably not a boost leak. what we did notice, however, was that we saw boost starting at 4k rpms and not at 3 k, we think this may be because either we did the test on the vag com at one second intervals, so we think it could be a delayed reading from the vag com or maybe delayed boost because of a vacuum leak?
after this we did the same kind of test on my friends '05 audi a4 1.8t (stock) and his boost started at 3k rpms, however we did some revisions and did the test at half second intervals.
when my engine is running i notice i hear some light hissing coming from the area where the throttle body/alternator is. don't know if its just in my head or if i'm just mistaking this for my serpentine belt running.
so in a nutshelll:
- dv fluttering when connected to n249.
-temp gauge rarely reaches 190 degrees.
- possible delayed boost.
what do you guys think? thanks in advance for any help!
