car runs like crap when cold

[PlanZero]

I have no problems starting my car on cold mornings, but if I don't let it warm up to operating temperature it runs like a slug. Today when I was leaving work I didn't let it warm up, and when I accelerated up a small hill it started making a "whoomp, whoomp, whoomp" sound, and bucked while doing so. I pulled over and it ran fine after warming up. Car is a 97 Tsi awd, bone stock except for apexi exhaust.

 

[Maes]

Temp sensor?

 

[PlanZero]

No problems starting, no matter how cold, so CTS is out. Last time I had a bad CTS it took 10 mins of cranking to start the car.

 

[Dxc545]

Have you checked spark plug gap? I have mine gapped tight, which makes engine warm up rough with the same symptoms.

 

[pauleyman]

Your diagnosis of temp sender is solely based on the fact it starts? Not very objective. Ecu gets fed info from sensors to determine what to do. Do you have any way to datalog?

 

[PlanZero]

Just changed plugs recently, but this was happening before. Gapped at .30. No way to datalog pauleyman, just going by what happened when I had a bad CTS before. For some reason I think this feels like an intake or turbo problem, if possible. Car isn't running rough like when I had misfire, or when bad CTS. It feels like there's resistance, if that makes sense. When it made that weird sound, it sounded like the exhaust, like a loud vacuum. I'm sorry if I'm not clear enough. I was going to try a boost leak test this weekend, but I'm not sure if these are symptoms, or if it's sensor related.
OK, so on my way to my second job tonight I noticed a hesitation when I boosted. Car was up to operating temperature.

 

[pauleyman]

Boost leaks would probably be worse when cold as the car is more rich when cold

 

[pauleyman]

Worse as in affects the car more.

 

[2ndGenOrDie]

Boost leaks and spark plug wires. I had a problem with my car where it would stutter through boost and I finally fixed it by changing spark wires. By any chance, is your FIAV still hooked up? Not being blocked off or bypassed?

 

[PlanZero]

I changed the plugs and wires at the same time, and there were symptoms before that, bit they seem to be getting worse, especially noticeable on short drives. Like I said, car is bone stock, except for the exhaust, so the FIAV is still hooked up. I'm hoping I just have a leak somewhere (does this even sound like a symptom?) Since its very possible one of the hoses has a crack that I can't see. One dummy question: when I make a leak tester as described in vfaq, do I need to block off the recirculation port on the bov?

 

[2ndGenOrDie]

Do a BLT and I bet you will have leaks all over. I did/do and am in the process of fixing them all. My problem seemed to go away with wires, but your car seems to be bogging not stuttering? Check all hoses for obvious signs of them being loose or not connected.

 

[Maes]

Another thing that is possible also is the throttle cable might not be adjusted properly. I had that issue before

 

[inthemidst]

I would check basics first.Compression test,timing,firing order, and a fuel pressure test and spark test.

 

[PlanZero]

So today I did a BLT and rented a vacuum tester, and I couldn't hear any leaks to my surprise. After I checked the condition of my hoses (all in decent shape, except for some wear from the clamps on the oil and coolant feed lines, which I'm replacing soon) I took Maes advice and checked my throttle cable. It was extremely slack, so I tightened it up a little. The car seemed to drive better instantly. The idle is now at 900, up from 500, and just feels and responds better. However, I noticed a throttle down surge (I don't know what else to call it) a couple times, when I let off the gas and the rpms instantly drop to 900, instead of gradual. Also, after putting the car into park (a/t) after driving the rpms rise to 1500-1700. Obviously, my problems are related to this, and I don't think my cable was necessarily the root cause. I don't want to screw with the biss unless I have to. I cleaned the tb a few months ago, with a new gasket, and tested my tps. I don't even understand how adjusting the cable raised my idle, if the throttle plate is still closing properly. Can someone please explain this?

 

[Maes]

When you adjusted the cable was the the engine at normal operating temperature?

 

[PlanZero]

Yes, I made sure of that. I even rechecked after driving around for a bit and there was still a little slack.

 

[inthemidst]

Check if your blow off valve is staying open when your idling.

 

[PlanZero]

Not to sound stupid, but how exactly? Take off the recirculation hose?