Cold start shakes

[hardcorecrayon]

Hey guys,

I'm just wondering whether I should get my car checked out. For the last couple of weeks, my beautiful 90 tsi has started shaking in the mornings for around 1min or so before returning back to normal. The shakes aren't violent but are still a little bit worrying. Is this "normal"? During this time, the tachometer reads just above 1000 rpm and then it slowly reduces down.

Thoughts?

Thanks,

edit: it has done around 120,000km

[CraigR]

Have the plugs been changed yet? Could also be a weak ignition coil - or worse, 1 or more cylinder losing compression due to wear.

[AdamD]

Idling above 1000rpm is normal for the first minute or so while the car is warming up. When you rev the car to the 'pre-warmup' engine speed once it's warm does it shake in a similar way? Do you feel any excess vibration, knocks or noises at other engine speeds? Any fault lights on the dash, or have you scanned the car for codes with a code reader or VCDS? Any reduction in performance or fuel economy?

[hardcorecrayon]

Idling above 1000rpm is normal for the first minute or so while the car is warming up. When you rev the car to the 'pre-warmup' engine speed once it's warm does it shake in a similar way? Do you feel any excess vibration, knocks or noises at other engine speeds? Any fault lights on the dash, or have you scanned the car for codes with a code reader or VCDS? Any reduction in performance or fuel economy?

The car drives perfectly when it's warm, no noises or knocks. There aren't any faults on the dash and I haven't scanned it for codes yet. I ordered an obdeleven last week so I'll be able to scan it when it comes in (hopefully in the next week). No noticeable reductions in performance & fuel economy.

I find it odd that it only happens after it has been sitting there overnight. Even if I leave my car parked at work for 8hrs, it starts up again perfectly.

Thanks for helping Adam!

[hardcorecrayon]

Have the plugs been changed yet? Could also be a weak ignition coil - or worse, 1 or more cylinder losing compression due to wear.

Just bought the car a couple of months ago and it has a full service history. The major service has also already been performed so I didn't think that I would need to change the plugs. But from what I've read, it's cheap and easy to replace. I'll do it in the next couple of days. Thanks for the tip! I sure hope that the cylinders aren't losing compression...

[Mk R]

Just bought the car a couple of months ago and it has a full service history. The major service has also already been performed so I didn't think that I would need to change the plugs. But from what I've read, it's cheap and easy to replace. I'll do it in the next couple of days. Thanks for the tip! I sure hope that the cylinders aren't losing compression...

Those engines are not known for decompression issues. The 118TSI does the same thing when ambient temperatures are between 20-30 degrees, like it runs super lean to heat up the catalytic converter quickly. A compression test is quick, easy and cheap to get done at your next service if you want to put your mind at ease.

[AdamD]

Yeah, haven't heard of any 90TSIs losing compression, and you'd be seeing fault codes and dash lights if there were persistent issues in that respect so I wouldn't be concerned. It's unlikely to be plugs or coils in my opinion because it wouldn't affect the car only when cold.

Have you sat in another 90TSI when started from cold? The car will only do the high-idle 'aggressive warmup' start routine if the cat, oil and everything else are stone cold, and sometimes having sat around for 8 hours after being driven won't be enough for it to lose all the retained heat. That's certainly the case with my Mk5 and my previous Mk6 GTI.

Because of the way these cars are designed to aggressively warm up the cat when doing a cold start (in order to get the cat up to temp and functioning properly as soon as possible, to reduce emissions), they often appear to run rough and shake a bit for the first 30-60 seconds. Just let the car sit idling during that time, and don't try and drive it until the idle drops to the usual ~720rpm. The shake is emphasised by the vibrations that often occur when an engine is revving around that 1100-1200rpm range. Honestly what you're describing sounds normal to me.

[hardcorecrayon]

Yeah, haven't heard of any 90TSIs losing compression, and you'd be seeing fault codes and dash lights if there were persistent issues in that respect so I wouldn't be concerned. It's unlikely to be plugs or coils in my opinion because it wouldn't affect the car only when cold.

Have you sat in another 90TSI when started from cold? The car will only do the high-idle 'aggressive warmup' start routine if the cat, oil and everything else are stone cold, and sometimes having sat around for 8 hours after being driven won't be enough for it to lose all the retained heat. That's certainly the case with my Mk5 and my previous Mk6 GTI.

Because of the way these cars are designed to aggressively warm up the cat when doing a cold start (in order to get the cat up to temp and functioning properly as soon as possible, to reduce emissions), they often appear to run rough and shake a bit for the first 30-60 seconds. Just let the car sit idling during that time, and don't try and drive it until the idle drops to the usual ~720rpm. The shake is emphasised by the vibrations that often occur when an engine is revving around that 1100-1200rpm range. Honestly what you're describing sounds normal to me.

That's reassuring, thanks! Maybe I'm just noticing it now because I'm paying more attention to it... I'll scan it for codes later and then I'll go from there.

Thanks for the help guys!

[fsures]

Higher milage direct injection engines can accumulate carbon on the valves. This manifests itself by having lumpy start up idle. Check the American forums for more info.

[hardcorecrayon]

Higher milage direct injection engines can accumulate carbon on the valves. This manifests itself by having lumpy start up idle. Check the American forums for more info.

Thanks for that fsures. Time to seafoam my car! I've always wanted to do this