severe bucking/overboosting

[Cesarlcase]

To get to the point My car is pretty much stock just a greddy b.o.v, t4 turbo and 2.5 inch exhaust. The car has been great since last summer;only 93 octane gas used. The problem with my 2g is whenever i give the car 2/4 of throttle it will buck severely,can't even go over 35-4000 rpm. But if i give it 1/4 throttle I could drive the car all the way up to 7k if i wanted. Pretty much the problem starts when the boost goes up, i could hear the turbo SPOOLING but no power.Once i release off the gas pedal and the boost goes back down,i could then give it more speed without the car bucking until the boost goes back up. I've read that it could be a leak in intercooler piping...idk if thats the case haven't checked yet. Also I'm guessing it could be a bad wastegate,is there anyway i could check if the wastegate isn't operating. Any other opinions would be much appreciated. Please help me out here. Don't want to give up on my car.

 

[90tsiawdturbo]

Id say the first place for you to start would be a boost leak test

 

[rlacasse1]

Boost leak first. That is what it sounds like to me.

 

[1bad4g]

x-3 on boost leak.....also check your base timing. (with timing light) next would be plug gaps. if thats all good. i would look in to bad FPR. or fuel pump about to kick.
do you have any dataloging stuff?

 

[Cesarlcase]

Yeah I'm going to bring it to a shop a.s.a.p to a boost leak test done,hopefully there is just a leak and can be easily found. unfortunately, I don't have any datalogging tools... do i really need one with my upgrades? I changed my spark plugs the other day with the ngk iridiums and 8mm ngk wires. The gap size is .30. Is that to big?

 

[gofer]

Yeah I'm going to bring it to a shop a.s.a.p to a boost leak test done,hopefully there is just a leak and can be easily found. unfortunately, I don't have any datalogging tools... do i really need one with my upgrades? I changed my spark plugs the other day with the ngk iridiums and 8mm ngk wires. The gap size is .30. Is that to big?

Gapping your plugs to .026 - .028 is optimal, was it bucking before you did the spark plugs? The symptoms your describing wouldn't suggest a bad wastegate, if it was the wastegate then your car wouldn't hesitate or buck it just wouldn't build any boost. Do a BLT (boost leak test) and make sure you get a reputable turbo knowledgable shop to do it, for me it meant taking it to a Mitsu dealer.

 

[sighless]

i just fixed this exact same problem yesterday morning by re-wiring my fuel pump./

i have owned the car for 6 months and spent so much time and money in parts.. and it turned out to be a 20$ kit to re-wire.

 

[Cesarlcase]

Gapping your plugs to .026 - .028 is optimal, was it bucking before you did the spark plugs? The symptoms your describing wouldn't suggest a bad wastegate, if it was the wastegate then your car wouldn't hesitate or buck it just wouldn't build any boost. Do a BLT (boost leak test) and make sure you get a reputable turbo knowledgable shop to do it, for me it meant taking it to a Mitsu dealer.

Yeah it was bucking pretty bad before i did the spark plug and wire change... Yeah i just might take it to mitsubishi. I'll Update everyone once i fix the problem. Dam this car has been stressing the life out of me. Now the BISS screw is f-ed up... I'm about to sell it and get a geo prism

 

[gofer]

...I'm about to sell it and get a geo prism

I'm going to forget you said that...

 

[Cesarlcase]

I'm going to forget you said that...

 

[Cesarlcase]

I had no leaks in my car and my car is throwing no codes besides o2 sensor bank 2... where is that located? i have a feeling that's the problem.

 

[gofer]

o2 sensor bank 2 is the rear o2 located in the exhaust behind your catalytic converter, unfortunately it wouldn't cause your car to buck/hesitate like that. The rear o2 sensor does nothing but tell the ECU that your catalytic converter is working properly, now the front o2 is a different story but your not getting a front o2 CEL.

I'm not sure how much boost your trying to run or really what modifications you have done to your car since your profile list is weak. I'm going to assume that what your seeing when you start going into boost (16psi +) your fuel setup can't keep up with the amount of air the turbo's pushing into the motor, so basically your seeing fuel cut. Update your profile mods list with EVERYTHING thats on that car that way maybe I can see something in your setup for you to look at next.

 

[95greentsi]

Did you upgrade your injectors, fuel pump, fpr? Sounds like your car is starving for fuel

 

[Cesarlcase]

o2 sensor bank 2 is the rear o2 located in the exhaust behind your catalytic converter, unfortunately it wouldn't cause your car to buck/hesitate like that. The rear o2 sensor does nothing but tell the ECU that your catalytic converter is working properly, now the front o2 is a different story but your not getting a front o2 CEL.

I'm not sure how much boost your trying to run or really what modifications you have done to your car since your profile list is weak. I'm going to assume that what your seeing when you start going into boost (16psi +) your fuel setup can't keep up with the amount of air the turbo's pushing into the motor, so basically your seeing fuel cut. Update your profile mods list with EVERYTHING thats on that car that way maybe I can see something in your setup for you to look at next.

Yeah,both of my o2s are bad! I was using a cheap scanner before. Brought it to autozone and they said both of my sensors are downed. So based off what you said, this very may well be causing this issue? Where is the front o2 sensor located and how would i go about removing it? . My car isn't heavily modded at all. Just a 2.5 exhaust,headers,CAI, t3/t4 turbo @8lbs, spark plugs and wires,and a new A/T transmission.

 

[WannaBeBoosted]

The front sensor is located on your 02 housing next to the turbo. Should be pretty easy to replace but the rear is located underneath the car basically where your drivers seat is located. Youll have to remove your seat to access the plug that needs to be unplugged in order to remove the rear 02. All in all id say a 1hr job. Good luck!

If you can manage to get your hands underneath the seat the perhaps you wont have to remove the seat to unplug it but id recomend doing so.

 

[gofer]

Heres a picture of the location of your front o2 sensor, its wiring goes over the top of your exhaust manifold (heat shield if you have one) and is plugged into a connector on the passenger side of the engine bay. It's physically located on the driverside of the turbo, in whats called the o2 sensor housing (for obvious reasons) and can be a PITA to remove depending how long its been in there.
I know the picture shows two sensors there but your car will only have one, the extra sensor you see in the photo is an EGT sensor and is aftermarket.

You must be logged in to view this image or video.

If your unsure where it plugs in at use this write up from Brian Front o2 sensor Connector Location.


If your low on cash you can get away with just replacing the front o2 sensor for now to fix your cars bucking problem, then get to the rear o2 sensor when you've got spare money lying around. o2 sensors can be pricey from auto parts store so I always refer my dsm buddies to NGK NTK Oxygen Sensors | BOSCH Oxygen Sensors | DENSO Oxygen Sensors because they are cheap. I suggest getting a can of PB Blaster to make life easier on yourself when removing it. When you install the new sensor you'll want to put some Anti Seize Compound on the threads so if you ever have to remove the o2 sensor again it will make life a lot easier.

 

[Cesarlcase]

Thnksz bro...just got my o2 sensor today,going to install it a little later and update about the results.Hopefully this cures the problem.

 

[Hesh724]

i was overboosting and stuff like crazy bucking and cutting at like 5g and boost was goin to like 20psi. it was the line split and it was sucking outside air. just a quick cheap thing to check i guess. good luck

 

[Cesarlcase]

Sry for anyone lookin 4 updates on the problem if they maybe experiencing the same thing...I was in Ohio for a bit... But Umm pretty much, I put the o2 sensor in my car and the overheating problem that I had is gone now but is still there somewhat... didnt really get to test the car considering its still the same. as of now,my final guesses at this, until i could find a reasonable price and knowledgeable turbo mech, would be either the cat is causing back pressure from probably being screwed up by driving with the bad o2/it already look really worn out be4 this even happened/rattling sound is really evident. 2 would be a stuck open wastegate allowing heavy overboost and the eventual buck.and 3 which I doubt is the fuel filter,which i heard causes similar problems. After that I'm a pick up the car walk to the Verrazano Bridge and just throw that mother-f***er... sorry guys,but Im a bit stress. Any opinions on my guesses are much appreciated.

 

[Orangedsm95]

You might be over running the fuel system.

 

[Cesarlcase]

You might be over running the fuel system.

what do you mean by that?

I changed the cat...nothing happened besides increase in speed but still bucks and now it overboosts even higher.

 

[colbyc]

Stock injectors? stock fuel pump? and im guessing you still have the side mount with the stock side mount piping....correct?
idk why you'd throw a t3/t4 turbo on there with out doing the fuel system first man.
You should get some bigger injectors and a fuel pump with preferbely fpr with gauge. Also do a boost leak test asap then come back with results, if you have a boost leak then start from there dont want to screw that pretty little engine up

 

[killer_eclipse]

what he means by over running your fuel system is that for the amount of air you are pushing into the motor there is not enough fuel to match because your fuel system hasn't been upgraded enough..... what exact fuel mods do you have ????? in none you need some what exact turbo are you running? based on that will be what kind of mods you need for your fuel system.what boost are you tring to run? Also what kind of wastegate are you running internal or external?

 

[JusMX141]

I changed my spark plugs the other day with the ngk iridiums and 8mm ngk wires.

Get the Iridium plugs out of your car, replace them with standard copper-core NGK's and gap them .026-.028" if you're under 20psi of boost. Just because a plug costs more doesn't mean it's actually better.

You might be over running the fuel system.

Can't believe it took 20 posts to get to what is probably the right answer.

Any fuel mods on this car? Bigger injectors? Fuel pump? Something to tune with?

Believe it or not, the stock injectors and fuel pump only go so far with an upgraded turbo.

 

[gofer]

Can't believe it took 20 posts to get to what is probably the right answer.

Just 12...

o2 sensor bank 2 is the rear o2 located in the exhaust behind your catalytic converter, unfortunately it wouldn't cause your car to buck/hesitate like that. The rear o2 sensor does nothing but tell the ECU that your catalytic converter is working properly, now the front o2 is a different story but your not getting a front o2 CEL.

I'm not sure how much boost your trying to run or really what modifications you have done to your car since your profile list is weak. I'm going to assume that what your seeing when you start going into boost (16psi +) your fuel setup can't keep up with the amount of air the turbo's pushing into the motor, so basically your seeing fuel cut. Update your profile mods list with EVERYTHING thats on that car that way maybe I can see something in your setup for you to look at next.