Strange low-idle & RPM drop-off

[Jacooooob]

Hello everyone. I have a stock 2010 GTI with 130k that I have noticed that after a short, casual drive the car will idle up to ~1200 while coming to a stop before settling at 800. If I blip the throttle, the rpms will ride out on their own for a moment as though I were still pressing on the pedal.

It almost seems as though my PCV may be failing or that I may have a vacuum leak causing weird A/F ratios? I had the water pump replaced about 600 miles ago, or two weeks, but have not had any issues until just a day ago. The car has no hesitation, no stalls, no sounds, and normal power while driving.

I also just ordered from ross tech to check live data and it should be here by week’s end. Any thoughts? Thanks

 

[BudgetPhoenix]

Idle surging is common symptom of vac leak. PCV is a common culprit. No codes yet? Also the PCV can fail in multiple different ways, one of the most common is a torn diaphragm which you can diagnose by putting your finger over the breather hole to the right side of the circular cap with engine idling, if its sucking air in its a blown diaphragm. Usually though when this happens it causes idle surging with really bad misfires. There's also an interval valve that can fail or maybe the gasket is leaking and warped which are more subtle vacuum leaks. Check around the engine too for any obvious loose breather hoses, intake & manifold leaks etc.

 

[Joe_Mama]

Probably needs a good carbon cleaning.

 

[jay745]

Sounds like symptoms of a vacuum leak somewhere

 

[sterkrazzy]

Would be worth checking the intake manifold too.

 

[Jacooooob]

It did throw a code yesterday. P2187, lean at bank 1. That’s a few outcomes unfortunately, and the scanner I ordered is also delayed shipping due to weather. I pulled the pcv off and the valve on the bottom seemed slightly offset/stiff, but then it started raining and I have no garage. I will put it back on and check the small port that mentioned for leak, but likely order another part and update.

Also, there were no issues prior to this. No rough starts, hesitations, loss of power, misfires, smoke, etc. It was running like a top. I also hear no audible leaks, but I’ll spray some carb cleaner around and see if it inhales any. Thanks for some insight

 

[chuck43]

i literally had random misfires last week, changed coilpacks & spark plugs - didnt fix it, still had multiple misfires. I then ordered a PCV valve from amazon (will replace with a delete kit and catch can when this one fails if not before) and that sorted it.

I will be getting my timing and chain tension checked now though as it scared me

heres the link for the pcv mine needed

https://www.amazon.co.uk/gp/product/B07KP8MC2T/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

Hope this helps

 

[Joe_Mama]

Don't buy knock off PCV kits. OEM only please.

 

[BudgetPhoenix]

Don't buy knock off PCV kits. OEM only please.

+1 on this I learned my lesson.

 

[Jacooooob]

Yeahhhh... so about those oem parts. If you could just uh have those on my desk by Friiiday that’d be great.

With quarantine squeezing me for that extra $120 I did buy a Gates brand pcv. It wasn’t the cheapest, but now I’m showing misfire codes P0300, 0303, and 0304. The plugs are healthy NGKs with the red coil packs and those look fine.

I had the VAGCOM come in, but I’m not too familiar with using it to diagnose anything internally. I’d like to measure timing chain stretch with it. First things first gotta run right

 

[Joe_Mama]

Yeahhhh... so about those oem parts. If you could just uh have those on my desk by Friiiday that’d be great.

With quarantine squeezing me for that extra $120 I did buy a Gates brand pcv. It wasn’t the cheapest, but now I’m showing misfire codes P0300, 0303, and 0304. The plugs are healthy NGKs with the red coil packs and those look fine.

I had the VAGCOM come in, but I’m not too familiar with using it to diagnose anything internally. I’d like to measure timing chain stretch with it. First things first gotta run right

lol

 

[chuck43]

yeah big fan of OEM, dont normally buy cheap but thats all i could get in a day (need car as daily still), the local Vag parts supplier are about as useful as chocolate fire guard. You could literally take them the part, and they would still look at you with cross eyes!
Either way, it diagnosed the fault quickly (still working btw) & now Im in the process of finding OEM part or delete kit and catch can. Im just about to go and work In saudi (as im a race mechanic we are classed as athletes so we are allowed to travel with corona) Once im back ill be on my own car again.

On another side note, just about to fit DV+ this afternoon

 

[Joe_Mama]

wow cool enjoy saudi arabia and dont bring any liquor

 

[Francoleon91]

are vaico PCVs no good then?

 

[Joe_Mama]

Don't buy knock off PCV kits. OEM only please.