View Full Version : B5.5 1.8T weird idle issues and AC acting up?

2013.08.15, 10:11 AM
I bought a 2001.5 1.8T with TipTronic earlier this year, and it's been doing this since I've had it. With it being warmer lately, I've actually been using the AC. It doesn't blow very cold, but it's better than the ambient air. I'm guessing it needs to be recharged, but there's another issue:

When in gear with the AC on, the idle seems to drop and then over compensates and tries to move the car forward. If I have the brake pressed, it squats the rear end and is pretty violently trying to move forward. I normally put it in neutral at lights and in traffic. There's times it doesn't do it, but it's more often than not. I have been averaging about 20-21MPG mixed with the AC. I ran this last tank without AC and it was about 25 mixed. I know AC hurts MPGs, but I know that's a big jump and there's obviously and underlying issue. What would be causing this weird surging?

Without the AC on, it occasionally has a slight drop in idle and then smooths out (nowhere near as aggressive as with the AC on). I just had all vacuum lines, DV, PCV and related hoses replaced. I thought it seemed to help at first, but driving it the day after I realized that it didn't. What else should I look into?

Rabbit 16v
2013.08.16, 09:55 AM
Codes? Buildup on throttle body near butterfly? log MAF.

2013.08.19, 05:42 AM
I didn't think about buildup around the TB...I'm going to check that out this week. As far as codes, there was an intermittent cam sensor failure but it hadn't been cleared in God knows how long and it didn't throw a CEL.

2013.09.09, 20:37 PM
Checked the TB butterfly and TIP, seems really clean to me (slightly oily, but no excess or puddles, just a thin film). I don't know when I'll be able to pull the codes next, but we'll see what that says.

Rabbit 16v
2013.09.10, 19:57 PM
Codes are very helpful. Have you taken the lower intercooler hose off to see how much oil is in there?

2013.09.12, 06:51 AM
Not yet, I was going to do that this weekend when I do an oil change on it. I should invest in a Vagcom cable... now that all 3 of my cars could use it.