When I start my car for the first time in the morning, it often catches, sputters and dies. The second try always works fine, except then it doesn't do a cold (high) idle for 30+ seconds, it goes straight to a normal idle. It's always done this on-and-off since I bought the car, but it seems to get worse as the weather gets colder. No error code gets thrown when this happens.

If I cycle the key on/off a few times before attempting to crank, it "usually" catches on the first try and stays at high idle for a while before the RPMs slowly drop to normal. Although sometimes it'll still initially sputter and threaten to die before regaining composure.

I thought maybe the 228,000 mile old injectors might be responsible, but I just replaced them with Bosch EV14 550cc injectors and the same thing happens every time.

All spark plugs, coils and coil harness are brand new, but it hasn't fixed the issue. The SAI pump no longer exists, and neither does most of the vacuum system (with the exception of the brake booster, PCV, evap, N75 and DV). However eliminating most of the vacuum system did not affect the problem one way or another.

I'm not sure where else to look for the cause of this issue. Other than the wonky start-up, the engine runs good as (better than) new under all circumstances. In fact, with the new injectors, it's so smooth at idle, I can't even tell it's running.

To me, an engine that sputters and dies at cold start-up is an indication of a failing part somewhere. Any other ideas where I should look? MAF? VVT? IAT? O2 sensor?

Thanks,

 

I had th

 

no combi valve, I removed it as part of the SAI removal. I've got a block-off plate there instead.

 

Try replacing the CTS (coolant temp sensor). It plugs into the coolant flange on the back of the head. This little item has been known to give cold-start issues.

Hold up... What tune does your ECU have? With our cars you're not supposed to just throw in higher-flowing injectors without the ECU being tuned for the injectors you put in.

 

Ah hah! Never even considered that. Should be a cheap thing to look into.

Stage 2 from J-Fonz Tuning, adjusted to run these specific injectors. I knew my old injectors were past their useful life, and Bosch EV14's turn out to be about the same price as new stock or TT225 injectors, so I figured I'd future-proof the engine for no extra cost.

 

It is indeed a relatively cheap part. If you have VAG-COM this is actually something you can diagnose too.

Ahhh that's better If your goal is to "future-proof" the engine, you may want to consider a 3-inch MAF housing as well. The stock turbo won't benefit from it, but an upgrade as small as a K04 could.

 

Just for grins, do a throttle body adaptation. Since you're having RPM issues, it may help out.

 

Thanks! I already did that, more than once in fact.

 

I was planning on that as part of my planned frankenturbo upgrade sometime next year. Meanwhile, the MAF appears to be functioning exactly as intended.

 

Are you still on the original fuel pump? It could be on its last leg, might be something to look into as well.

Don't forget the filter as well!

Jason