Why does my car run like crap when it's cold?

[X-ZZ4]

I don't mean cold outside, I mean like sitting over night and starting in the morning.

It's done this ever since I bought it, but I've had bigger issues and ignored this because it runs ok when it warms up. But now I got most everything else fixed (at least for now)....So I'd like to knock this one out now if I can.

Start it in the morning. Runs like it misses, but there's no codes. If you don't let it warm up for a minute. It feels like it has no vacuum also because the brakes barely work also. Give it 30 seconds, brakes come back, give it a minute, runs fine.

Is there a "warm up sensor"...lol?

Help on where I should begin troubleshooting is appreciated.

Thanks!

[G0to60]

You could try replacing the coolant temp sensor. I'm not sure if it's exactly the same but some of my older cars would run like crap when cold if this sensor was bad. It's also nice that they are cheap and easy to swap out.

[carmudgeon]

On a car that old its conceivable that you may have multiple issues but it sound like at the very least you have a vacuum leak.

[02 A6 2.7T]

On a car that old its conceivable that you may have multiple issues but it sound like at the very least you have a vacuum leak.

^^ X2 . My 2002 6MT has what looks like a tee fitting in a hose running from the underside of the accordion hose, with one line running to the power brake booster. The tee fitting on mine came apart and caused the same symptoms; the tee is actually called a "suction pump" and is part of this assembly: https://www.ecstuning.com/ES2664091/...FY17fgod4yUIGQ
I glued mine back together with 5 minute epoxy ... 7 years ago ...

[X-ZZ4]

On a car that old its conceivable that you may have multiple issues but it sound like at the very least you have a vacuum leak.

Thanks for the help. I didn't know my car was old. Now this solves everything.

[X-ZZ4]

^^ X2 . My 2002 6MT has what looks like a tee fitting in a hose running from the underside of the accordion hose, with one line running to the power brake booster. The tee fitting on mine came apart and caused the same symptoms; the tee is actually called a "suction pump" and is part of this assembly: https://www.ecstuning.com/ES2664091/...FY17fgod4yUIGQ
I glued mine back together with 5 minute epoxy ... 7 years ago ...

Did your symptoms only occur cold? I would think a vacuum leak would cause other problems as well. Mine runs fine once it warms up a bit.

[a4kamila6]

Whatever is leaking expands when the engine warms, thats why it feels a little better. I would check every visible connection or joint you can. Touch the vacuum lines, bend em back and forth a little. Thought mine were great and then i just touched it them and revealed a crack right by where the line meets the diverter valve for example. Hear any hissing?


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