Stumbling/hitting a wall in lower rpms

First off I have no check engine light at all

 

I have this weird like stumbling/bucking/like the car is almost hitting a wall in the lower rpms, mainly below 3k is when I notice it it's not like extremely harsh, but it will slightly kinda her so to speak, I'm at a complete loss

 

All mods are open sources tuned threw a reputable tuner, and the car did this before hand too

 

Mods include basic bolt ones, exhaust, vf52 turbo, dw65c, Cobb intake

 

I've checked vacuum lines and didn't see anything out of the ordinary, I've check all connections and nothing seems out of place

 

I don't even know we're to start with this? Any ideas would be greatly appreciated

Have you been able to get any ideas out of your tuner? Sometimes they can point you in the right direction. The fact that it happened before the tune tells me it could be mechanical?

Before I had it tuned I mentioned it, but ironically the car didn't really do it, and nothing showed up while tuning that he was able to point me in any sort of direction, he kinda shrugged it off since it didn't really do it when he was tuning

 

That's the thing if I drive it lightly (light on the gas) below 3k it pretty much doesn't happen, but if I kinda drive it aggressive and give it more gas below 3k as I'm shifting i can almost guarantee that the car will buck/stumble it's almost like something is just holding the car back

 

Kinda like a misfire, but idk if I would exactly say it was a mis fire

check all vaccuum lines again, clean your MAF sensor

I will clean the maf sensor again, but I cleaned it prior to the tune, and I've checked vacuum times a million times and I'm still not really finding anything out of place

 

Car also idle fine, doesn't fluctuate

Fuel pump?

Fuel pump was just replaced with a dw65c, I thought maybe it would help as well, but did it before and after the fuel pump

Check your grounds. Especially the grounds on the underside of the car. There's one on the passenger side that goes from the exhaust manifold heat shield to the frame. And another on the driver's side head to the frame. Make sure the connections are clean.

 

Also I would do a boost leak test since they are easy and can lead to big problems with tuning.

It could also be an OCV (Oil Control Valve) that is intermittently sticky.

 

Normally they throw a code, but stranger things have happened.

 

Here are a couple of links to help.

 

http://legacygt.com/forums/showthread.php/p0011-p0021-missfire-ocv-oil-flow-control-valve-141880.html

 

http://legacygt.com/forums/showpost.php?p=1943328&postcount=8

Yea a local told me to check the ocv as well

 

Best way to clean it?

OK so I'm going to bump this thread a little bit

 

I have pulled and cleaned both ocv, and neither of them really needed a cleaning, both functioned as should

 

Replaced front o2 sensor with a oem sensor, no change at all

 

Cleaned maf sensor, no change at all

 

Replaced both lower grounds under the engine, and the main one behind the tmic, no change at all

 

I'm honestly at a loss, no cel, seems to only really happen when the engine isn't full warmed up, but has on rare occasions done the same thing while the engine was fully warmed up

Have you logged this? I bet the ECU is pulling timing due to (perceived) knock.

I have not, but I'd assume that my tuner would have noticed it and said something

If it didn't happen when he was logging, then he wouldn't have seen it. You should log the car on your regular driving and when it happens, do something in the log to make it obvious where it happened (blip the throttle a couple times, etc). Then post it here or send it to your tuner.

And even if that were the case, why exactly would that mean or what would the fix be? Better tune? New engine?

How exactly would I log it? I don't know much about the tuning aspect of things

If it's just a little knock correction (whether it's real or not), then yes, likely you could tune it out. That's not to say anything negative about your tuner, but there's a reason tunes need revisions.

 

If you need help logging, you're probably best talking to your tuner. If you're using a Tactrix OP, there are ways to log without any extra hardware (directly to a microSD card). I log to my in-dash Android tablet using BtSsm, but you could also use a laptop.

OP: If you do want to log the car, there is a cheaper option than a Tactrix cable since you have an 05. I've been using a cable like the following for the last month or so without issue:

 

https://www.amazon.com/FT232RL-409-1-K-Line-KWP2000-ISO9141/dp/B00LJM9AHC/ref=sr_1_1?ie=UTF8&qid=1493677031&sr=8-1&keywords=VAG+KKL+OBD2+FT232RL

 

Mine was a different one that is apparently unavailable now, but the chip is the same.

 

This also helped me:

 

http://www.romraider.com/forum/viewtopic.php?f=33&t=5384

Well that's interesting

Oh, and this is a rabbithole I've been going down lately while chasing a misfire. Sound like your problem at all?

 

https://forums.nasioc.com/forums/showthread.php?t=2732703

I was reading about that the other day, or at least I came across the fpr kit

 

I mean kinda, but it's not really at 2800 rpms, it usually happens more so around 2k

 

Sonetines it's a very minor like "surge" you could call it I guess

Best way to describe it, is it feels like the car is in like 5th gear, going 25mph, and I'm giving it gas to go faster, we're it kinda hesitates and bucks so to speak

Get a cable. Get RomRaider. Take a log when it happens. Compare your accelerator angle to the throttle body angle. They should be identical. If they're not, your throttle body is likely failing.

 

Same thing happened to me. 203K on the original one.

The majority of us has issues with the FPR (Fuel Pressure Regulator), there are a few simple tricks to correct this or run a different FPR.

 

Here's the link: http://legacygt.com/forums/showthread.php/famous-stumble-fixedi-232816.html

 

 

Others that found different fixes:http://legacygt.com/forums/showthread.php/stumble-stutter-thread-182559p19.html

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