View Full Version : sputtering upon cold start up

03-05-2014, 05:49 AM
This has been happening for a while and I can't seem to figure out the cause, I've replaced the injectors (from 440cc to 550cc)
Loaded the programming for larger injectors, changed the O rings on the injectors, changed the under the hood fuel lines, and fuel line clamps.
My fuel pressure sits no lower than 18 psi even after the car has been sitting for days, it always starts right up, but when the engine is cold if I touch the gas pedal it sputters briefly acts like it's going to die, once it warms up a little it no longer sputters.


In the video it's hard to hear but the sputtering can be heard, this issue is driving me nuts

03-05-2014, 05:56 AM
I've also changed the fuel injector cups to the billet ones from verdict motorsports.

03-05-2014, 09:26 AM
have you tryed cleaning maf, throttle body and such?

03-05-2014, 09:33 AM
Small vac. Leak maybe

Mad Cow
03-05-2014, 10:01 AM
Coolant temp sensor maybe? What does vcds say your temperature is on cold start?

03-05-2014, 06:56 PM
The coolant temp sensor was replaced with a OEM in late september right before I parked it for winter.
as far as the Maf and Throttle body I havent cleaned those in a while so thats a idea there.
Ill have to plug in the vag com when i get home to see what the temp is (what block is that? I dont remember)
It also has fresh bosch f6dtc plugs.

It only does the sputtering when the engine is cold, if it warms up a little bit and i start it again it doesn't sputter, its only upon cold start up.
It doesn't smell like it is running rich, a boost leak test will be preformed real soon after i get done installing my new front mount intercooler, I normally boost leak test it after I replace or remove anything related to vacuum.

I also dont use the n249 valve it is plugged in and has the vacuum line looped back to it, I just removed the SAI system this past weekend I dont have the program with it written out yet, but this issue was going on before I removed the SAI system, the N249 has been bypassed for about 3 years now and this issue has been going on for about a year now (I dont drive this car much)

03-09-2014, 09:04 PM
I think i found the cause of this issue, but that was after I put in efforts to change the exhaust manifold to turbo which became a massive mess.

what I think is the cause is 2 of the three nuts that hold the turbo to test pipe together wiggled loose, so upon cold start up it would suck in air the O2 sensor would see it and freak out, I had this happen once before but i also discovered the exhaust manifold to turbo gasket got a hole burned through it (got to love bolts that stretch) so last time i did this I replaced the bolts with 10.9 grade, used anti seize and though my troubles where over boy was I right but wrong at the same time, when I finally remembered this gasket being the possable cause I started taking things apart to get to the bolts on top of the turbo, and this is where the mess began I get out my 17mm open end wrench and loosen up the inside bolt a little, I then move to the front two and they wont budge so i put a little more muscle into it POP!! bolt is loose as can be and broke, after a few choice words, I try the next one POP YAY another broken bolt!!! more choice words, I remove the manifold to turbo gasket and.......it was just fine, than after removing the turbo inlet and everything else but the oil and coolant lines to the turbo, I drop a screw driver and it gets stuck between the motor and test pipe as i get the screw driver out I notice the test pipe is loose, I look further and the nut closest to the motor is loose and the one on the bottom, Bam!! it hits me that was a possiable cause the last time and now i felt like a total idiot!!
anyways I spent all day Saturday getting those stupid broken bolts out I ended up drilling them out and using heli coils, I havent started it up yet bolt the turbo bolts up like it should and this time ill be using 8.8 grade bolts a little stretching here and there is much better than no stretching and breaking.


03-09-2014, 09:14 PM
Sorry to hear about your trouble with broken bolts, they can be a real pain in the ass. I've broken two turbo-manifold bolts, both the outside bolt. One at the junkyard as I was pulling the spare turbo out, and once on my car when pulling my old turbo out. Luckily I was able to drill out the broken bolt and run a tap through it without having to drill out the hole and use a helicoil. I'd recommend sticking with stock bolts, I think any bolts that are in the car for 100,000 miles around the turbo are bound to break, but you shouldn't have trouble with new bolts so long as you use high temp copper anti-sieze.

Not sure I would agree with your assessment of air being sucked into the exhaust, for the sole reason that the exhaust system is always under positive pressure, not vacuum.

Have you tried cleaning your throttle body?

03-09-2014, 09:58 PM
I have the franken turbo high flow manifold, the good old trusty stock bolts are a little on the short side, I cleaned the throttle body and intercooler piping prior to all this, and I got the same results as before, I also tried a throttle adaption with the same results.