4G63 Turbo bogging down under boost

[poppabear]

i actually have 2 questions.

1. For some reason if i was driving and decided to tip in to the throttle heavy, once it hits high boost it wants to bogg down. almost as if it was choking out, getting to much air or possible boost leak ? i have no CEL on and this is a stock 4G63 Turbo engine. What are some area's i can check to narrow it down ? If i give it gas slowly it will move just fine, but while in higher boost and heavier throttle it wants to sputter/spit/bog/choke, which ever word you like to use to describe it.

2. At 80 mph in 5th gear the car runs @ about 3,600 RPM's ... is this about right ? If not what should i be running @ and what are some possible reasons behind the high RPM's ?


Thanks for the help.

Remember, this vehicle is a completely stock 4G63 AWD Turbo
95 Eagle Talon Tsi

Thanks,
Mike

 

[rush2252]

Hello there Mike Welcome to the site!

To first address the problem your having you must first understand that the 2nd generation turbo cars were designed with some flaws. The first of which is the rich factory fuel maps. The cars run extremely rich from the factory. You either learn to deal with it or tune it. Secondly the plastic Blow off Valve or Pressure Release Valve that sits directly above the transmission inline with your upper Intercooler piping leaks. It leaks at idle it leaks at wide open throttle and even cruising speeds. You can confirm this by starting the car and removing the recirculation hose and visually seeing the diaphram opening and the boost charge leaking by. And third the stock T-25 turbo while spooling quickly isnt made for top end performance. It spools around 2800rpms and peaks at around 5000.

I believe with a combination of these will probably be the cause of your noticable "bog" under Wide Open Throttle.

One of the cheapest fixes is to purchase a 1g blow off valve. They can be found for around $40.00 I think there are a few in the classifieds. You will either have to modify your piping or buy the adapter. Either of which this should take care of some of the problem.

The 1g cars run between 12-14psi boost from the factory and the 2gs run around 8psi. BUT the 2g BOVs leak they always have and usually over time they get worse when the spring gets weaker.

Hopefully this will give you some insight
Kolby

I forgot to mention.. You might want to perform a boost leak test. You can search it and its fairly straightforward. Keep in mind also the stock boost gauge is useless. It doesnt actually read Manifold pressure. It reads from the MAF. It reads air being drawn through and guesstimates the amount of boost being put into the intake charge. You could very well just have a boost leak this could also account for some of the problem

 

[JEFFREYCASTGSX]

Hello there Mike Welcome to the site!

To first address the problem your having you must first understand that the 2nd generation turbo cars were designed with some flaws. The first of which is the rich factory fuel maps. The cars run extremely rich from the factory. You either learn to deal with it or tune it. Secondly the plastic Blow off Valve or Pressure Release Valve that sits directly above the transmission inline with your upper Intercooler piping leaks. It leaks at idle it leaks at wide open throttle and even cruising speeds. You can confirm this by starting the car and removing the recirculation hose and visually seeing the diaphram opening and the boost charge leaking by. And third the stock T-25 turbo while spooling quickly isnt made for top end performance. It spools around 2800rpms and peaks at around 5000.

I believe with a combination of these will probably be the cause of your noticable "bog" under Wide Open Throttle.

One of the cheapest fixes is to purchase a 1g blow off valve. They can be found for around $40.00 I think there are a few in the classifieds. You will either have to modify your piping or buy the adapter. Either of which this should take care of some of the problem.

The 1g cars run between 12-14psi boost from the factory and the 2gs run around 8psi. BUT the 2g BOVs leak they always have and usually over time they get worse when the spring gets weaker.

Hopefully this will give you some insight
Kolby

2g's run the 12psi and 1g's run 8psi

 

[rush2252]

2g's run the 12psi and 1g's run 8psi

Im not going to get into an argument on the forums. But IVE tested both the T25 stock wastegate actuator and the 14b actuator. Im swapping to a 14b. My initial statement is true althought ive seen a few T25s hold 10psi before opening but this could be a fluctuation in the method and gauge being used. Keep in mind they bumped compression on the 2gs as well this is the reason for the lower boost levels.

Test Results: 14b/16g stock WGA opens at 12-13psi
Test Results: t25 stock WGA opens between 8-10psi

Keep in mind he is BONE STOCK meaning he still has the boost control solenoid hooked up.


Kolby


TO MIKE: Do a search on removing the stock BOOST control Solenoid as well. You can simply run a vacuum line from the nipple on the stock T25 compressor housing to the Wastegate actuator this should allow you to run the preset boost for the stock wastegate.
If the car is in fact bone stock it should have a T'd line running from the boost solenoid then to the BOV and the WGA keep the solenoid plugged in but route the vacuum lines as I stated. This will also help maintain your desired boost and if you leave the solenoid plugged in you should never see a Check Engine Light

 

[allthrottle]

I have a near stock 1g with a big 16g. My factory and autometer boost gauges are telling me I'm holding steady at 9psi. This is with the bcs restrictor removed. I've read the 1g's boost 8lbs and the 2g's closer to 14psi. I haven't done much research or testing, but this seems consistent with what I'm currently experiencing.

As far as the cruising rpm, that seems about right. If you're used to driving a big v8, I can see how that seems a little high for 80mph, but this is actually on the low side for most 4 cylinders. I have a scion xa that will be close to 4k rpm at 70mph, and all of the Honda's I've owned were about the same.

I have a similar bogging issue when not fully up to temp, regardless of how close it is. The logs lead me to believe mine is o2 sensor related, as it doesn't start showing any o2 voltage fluctuation until warm. You could look into a new o2 sensor if you have not yet, and you should also do a little researching on how to properly test and set the tps. That, a boost leak test, and checking the engine and ignition timing should help you diagnose your problem, and won't cost you much.

 

[92dsmgst]

I have a nearly bone stock 92 gst and i build up to 14 pounds on the factory gauge and roughly 16 on the aftermarket one....

 

[Jeff99GS]

i actually have 2 questions.

1. For some reason if i was driving and decided to tip in to the throttle heavy, once it hits high boost it wants to bogg down. almost as if it was choking out, getting to much air or possible boost leak ? i have no CEL on and this is a stock 4G63 Turbo engine. What are some area's i can check to narrow it down ? If i give it gas slowly it will move just fine, but while in higher boost and heavier throttle it wants to sputter/spit/bog/choke, which ever word you like to use to describe it.

2. At 80 mph in 5th gear the car runs @ about 3,600 RPM's ... is this about right ? If not what should i be running @ and what are some possible reasons behind the high RPM's ?


Thanks for the help.

Remember, this vehicle is a completely stock 4G63 AWD Turbo
95 Eagle Talon Tsi

Thanks,
Mike

Have you done your basic maintinence? On top of what the other guys mentioned I would clean/check/ and gap your spark plugs. Or get new ones. NGK Copper core BPR6ES.

Also...what kind of fuel you running?

 

[poppabear]

Have you done your basic maintinence? On top of what the other guys mentioned I would clean/check/ and gap your spark plugs. Or get new ones. NGK Copper core BPR6ES.

Also...what kind of fuel you running?

The first thing i did was change plugs, went with NGK Platinum.

I'm running premium unleaded fuel, i think maybe Octane 93 ?

Not sure, Speedway's Premium Unleaded fuel.


BTW: I am a Service Manager at a shop so i have access to the tools and resources, just need to know in which area's i should be checking.

I'm going to check TPS and WOT today and make sure we are getting good responses from the TPS ... maybe delayed responses could cause the fuel not to adjust fast enough with the extra air coming in ?

Anyways, thanks all for the help so far, i will update you on the TPS test results after work.

Mike

 

[Jeff99GS]

Platnum plugs are NOT the greatest plugs for our cars. I had a TERRIBLE experience with BOSCH platnum. They fouled out and misfired after 2 weeks of use. The Electrode is TOO small. They may last LONGER than a copper plug but the copper has a larger spark surface.

Do a boost leak test too. If you're leaking boost pressure the car will run really rich and BOG.

 

[Dsmj89]

As mentioned above. Make sure you do all your maintenance first. For spark plugs, i recommend you run ngk bpr6's for your setup as you are fairly stock and running stock boost levels.
Do a boost leak test, and change that garbage bov.
If you can find an evo9 bov get it, it pops right on to your stock intercooler pipe and has a really stiff spring, holds boost wonderfully.

 

[poppabear]

First, thanks for all the advise. I am going to change plug wires then move to checking the boost leaks.

Something i may have forgotten to say that may help diag this issue.

When i sit in 'N' and REV the engine, i should be creating boost .. no ?

I can rev all the way upto like 6k and still barely move the stock boost gauge ... i don't hear any BOV either ..... HOWEVER, if in gear and driving it seems to be creating boost and on a good run i may hear a BOV ..... i assume this is NOT normal ... Possible bad turbo ? Maybe bad turbo causing the bucking, bogging, sputtering ????

Let me know your thoughts and ways to diag some of this.

Thanks,
Mike

 

[viperbenz1]

i would do a boost leak, i had the same problem i couldnt go over 10psi and the car choke at 5k

 

[TrevorS]

First, thanks for all the advise. I am going to change plug wires then move to checking the boost leaks.

Something i may have forgotten to say that may help diag this issue.

When i sit in 'N' and REV the engine, i should be creating boost .. no ?

I can rev all the way upto like 6k and still barely move the stock boost gauge ... i don't hear any BOV either ..... HOWEVER, if in gear and driving it seems to be creating boost and on a good run i may hear a BOV ..... i assume this is NOT normal ... Possible bad turbo ? Maybe bad turbo causing the bucking, bogging, sputtering ????

Let me know your thoughts and ways to diag some of this.

Thanks,
Mike

Reving the engine in neutral takes very little power, and so the exhaust flow is very low. Consequently, unless there is a real load being presented to the engine, there will not be any boost generated.

 

[poppabear]

ok, so i did the boost leak test, found a cut in the brake booster hose, replaced the hose and boost leak tested again, all seems good .... test drove and still has the bogging down issue ...

These are possible area's i can think of.

1. fuel filter - causing fuel cut and choking ok (running lean)
2. ign wires - braking down under high RPM's
3. ign coil pack('s) - braking down under high RPM's
4. fuel injector('s) - stuck open or closed (running rich or lean)
5. exhaust leak
6. bad turbo - checked shaft play today and have ZERO SHAFT PLAY ...
7. throttle body gasket leak - sprayed with throttle cleaner and made no difference in idle
8. turbo gasket('s) leaking - i do not know any other way to test for this besides boost leak test.


I'm not sure what is wrong or any ways to check AFR from stock ECU Data .. i have access to scan tools ect... as i am a service manager at a full auto service center.

Out of the list i provided if you guys can eliminate some from or add some to the list that would help. What area is most likely the issue, i work from a VERY tight budget ( i expect it to get better soon) and need to not just start replacing parts till its fixed as i want to spend the money tward upgrades/mods.

Little bit of info:

95 Talon Tsi AWD - T25 stock turbo (car is completely stock)
- took restriction out of the BCS (bypassed BCS, ran straight from compressor housing to WGA <- wastegate ?) <- yes i know, newb right
- Adjusted throttle cable and TPS to 100% WOT

- Vehicle runs fine under lower RPM's ...
- Vehicle runs fine on WOT while in lower boost levels, as soon as the stock boost gauge gets to the first line for the "+" boost it starts to bog, i have to let off the throttle just slightly and she goes right on down the road.
- If i am say at 4,500 RPM's then go WOT it seems like it runs with no issues.
- When at idle i can take RPM's up as far as 7k without a single misfire or stutter.
- Seems like i go through fuel like crazy, but this may just be the way i am driving it

Well, anyways i am BEGGING you professionals to help me diag this issue and point me in the right area so i can finally feel better about my purchase. I have big plans with the vehicle and plan to share everything with the dsm community.

If i can take advantage of the scan tool to grab any more info that you guys need to help me further, i will provide whatever you need to help me out. Thanks a bunch in advance.

Mike

 

[TrevorS]

Given you've performed a boost leak test, and after replacing the brake booster vacuum hose, there are no further leaks. If your plugs and gaps are as stock and in good shape (also the HT wires), and your fuel and air filters are also good, I would take a look at your O2 sensor. If you're running stock ECU, MAF, injectors, fuel pump, and FPR, plus fuel and air are present, and the plumbing is tight, something is throwing off your ECU and that strikes me as the most likely culprit. (Any ECU codes?)

 

[poppabear]

Given you've performed a boost leak test, and after replacing the brake booster vacuum hose, there are no further leaks. If your plugs and gaps are as stock and in good shape (also the HT wires), and your fuel and air filters are also good, I would take a look at your O2 sensor. If you're running stock ECU, MAF, injectors, fuel pump, and FPR, plus fuel and air are present, and the plumbing is tight, something is throwing off your ECU and that strikes me as the most likely culprit. (Any ECU codes?)

No, there is no ECU codes at all.

So first steps from what your post states is the following.

1. replace wires with HT Wires
2. replace fuel filter
3. check 02 sensor

Is this correct ?

Mike

 

[TrevorS]

No, there is no ECU codes at all.

So first steps from what your post states is the following.

1. replace wires with HT Wires
2. replace fuel filter
3. check 02 sensor

Is this correct ?

Mike

Excuse me, by long habit I identify the spark plug wires as High Tension (due to the voltage). Just make sure they are in good condition, not old. Replacing the fuel filter is a good precaution if you're not sure of its condition. You don't mention the air filter, so apparently it's known to be good. The O2 sensor can be bad and the engine will still run, though with a rich AFR. However, in that situation, it's not presumed boost will work properly -- the goal is just to keep the engine running until the problem can be corrected.

As a side note, if your stock intake hose (from the MAF/air canister) has any inlets that are open to the atmosphere, they shouldn't be!

 

[poppabear]

Excuse me, by long habit I identify the spark plug wires as High Tension (due to the voltage). Just make sure they are in good condition, not old. Replacing the fuel filter is a good precaution if you're not sure of its condition. You don't mention the air filter, so apparently it's known to be good. The O2 sensor can be bad and the engine will still run, though with a rich AFR. However, in that situation, it's not presumed boost will work properly -- the goal is just to keep the engine running until the problem can be corrected.

As a side note, if your stock intake hose (from the MAF/air canister) has any inlets that are open to the atmosphere, they shouldn't be!

No openings in intake at all, i will replace wires and fuel filter tomorrow, then test drive her again, if not fixed i will check into an 02 sensor. Thanks for the help and i will update you guys tomorrow, for now good night

 

[poppabear]

ok guys, i have found another leak while doing the BLT .... its a screw thats in the throttle body, i have tried tightening it down and still leaks, what is this screw for exactly ? what can i do to seal it up ?

Thanks,
Mike

 

[nytescion]

Base idle set screw probably. It's used to set your idle. you might just need a new oring on it to seal it up.

 

[poppabear]

yea, well its def leaking .... and i just need to replace the screw itself instead of replacing just the oring ... can anyone suggest a vendor for this BISS ... I'm not trying to pay $10 for just a plastic screw

Thanks,
Mike

 

[TrevorS]

ok guys, i have found another leak while doing the BLT .... its a screw thats in the throttle body, i have tried tightening it down and still leaks, what is this screw for exactly ? what can i do to seal it up ?

Thanks,
Mike

I'd recommend posting a photo of the screw and its location before going any further. Also, if you don't have a Haynes or Chiltons manual for your car, I'd suggest getting one since that might also help with identification, plus ongoing issues and questions !

 

[poppabear]

I'd recommend posting a photo of the screw and its location before going any further. Also, if you don't have a Haynes or Chiltons manual for your car, I'd suggest getting one since that might also help with identification, plus ongoing issues and questions !

Well, i know what it is now .... its the BISS ...

Just need to know where a good place is to order it and get it quick ...

another thing:
picking up my 1g BOV tomorrow or monday .. comes with the 1g flange tube .. will i be able to make that work ?

Thanks,
Mike

 

[poppabear]

Ok, well i have replaced the BISS oring and done another BLT and all seems good, still having the bog issue.

I noticed a small exhaust leak around the exhaust mani that i do not believe is cause the issue. Its where a bolt had broken off into the Head, but it seems to be very minor.

I now fail to believe its a Boost Leak, i feel it may be in the fuel area ..

I think that if it was ignition issues (wires/plugs/coils) it would throw a CEL and also do it while in nutral reving the engine up.

I wish i knew what it was tho so i could finally fix the issue. Bought ready to give up

Anyone with anymore feedback would be helpful.

Thanks,
Mike

Also, please comment on the post above regarding the 1g BOV. My 2g BOV leaks at very low psi, like 5-6psi. Thanks.

 

[4cyls_of_fury]

does your scan tool have a graphing option? if so i would check the maf under load.