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Choppy when going into boost?

Joined
Aug 21, 2012
Messages
11
Location
Tallmadge, Ohio
I just finished with my build on my 1991 Galant VR-4, she sat in a barn for 9 years and my buddy and I saved her before the barn fell in. Upon getting the car home the motor was taken out finding a massive crack in the block I bought a used motor and sent off to the shop to be built. Wiseco 8.5-1 pistons 1g rods, both block and head were machined. The head was fitted with all stock components. After installing everything back into the car I added a Megan racing 3-inch downpipe going into a magnaflow cat and a straight 3-inch pipe all the way to the back and a walbro 255. It has a 14b and everything is stock. Anyways, the car drives great, however when getting into boost the car breaks up and wont accelerate, the car begins to sputter but wont drop boost or die. I've changed the coilpack, ignition module, spark plugs NGK BRP7ES gaped to 25, NGK spark plug wires, MAF, Fuel pressure regulator, and installed a Hallman MBC and a autometer boost gauge, still no change on any front. Any help would be appreciated. Thanks
 
Last edited:

James

Well-known member
Joined
Apr 7, 2012
Messages
1,322
Location
Port richey Florida
Plugs might need to be a hair wider, did you check for boost leaks yet?
 

desant78

Well-known member
Joined
Jun 23, 2010
Messages
732
Location
Clarksboro, NJ
What boost are you running? Also is there any engine management in place? You might get more help with these questions.

And the dumb question: Did you set the base timing?
 
Last edited:
Joined
Aug 21, 2012
Messages
11
Location
Tallmadge, Ohio
It was running 8lbs before the boost controller and now I turned it up to see if it was just getting too much fuel, no change. There is no engine management and base timing was set. I am waiting for my buddy to get his boost leak tester.
 

mikus

Well-known member
Joined
Jan 11, 2007
Messages
2,763
Location
Aurora IL
you'll find a boost leak for sure. Get down to home depot and build your own tester!
 

JNR

Well-known member
Joined
Apr 23, 2004
Messages
9,814
Location
ca
EDIT - NM, saw the new ignition wires...
 
Last edited:
Joined
Aug 21, 2012
Messages
11
Location
Tallmadge, Ohio
After the long process of getting a boost leak tester, I've finally built one and found the time to do it. Found a big leak at the boos controller so I took it off and ran it with the normal circulation. Took the car out on the highway and I could build 10lbs in every gear it wasn't breaking up. After about 10 min of driving the same problem came back. Got it back fixed the leaking parts of the boost controller and hooked it back up, still breaking up in boost. I've noticed that if I hol it while its breaking up it will keep blowing off like I'm letting off the accelerator. Don't know where to go from here any help is much appreciated.
 

James

Well-known member
Joined
Apr 7, 2012
Messages
1,322
Location
Port richey Florida
First off you should do the leak test without the MBC.

You should also do another leak test. If you found a big leak early in the tract (at the waste gate), then you could still have plenty more leaks all the way up to the intake mani.
 

James

Well-known member
Joined
Apr 7, 2012
Messages
1,322
Location
Port richey Florida
For reference here's how my leak testing went when I got my car... These were all leak spots

Turbo to Jpipe
Jpipe to licp
Intercooler to uicp
BOV flange
BOV diaphragm
TB elbow to TB
TB shaft seals
Fuel rail Orings
Intake manifold

Now this was an extreme case and I hope
It's not the same for you. My previous owner
Was just dumb as f***.
 

5OF2k

Well-known member
Joined
Mar 28, 2012
Messages
664
Location
colorado springs, colorado
I concur with everyone else, you have boost leaks. Easy way to help locate them is to mix up a little dawn dish soap and wter in a spray bottle, and spray everything down as it's pressurized(couplers, hoses, intercooler, intake manifold, flanges, etc etc etc). Also, if you're running the factory BOV, disconnect the recirc pipe while you're doing the leak check. Chances are the diaphragm on the stock BOV isnt holding anymore and thats where its leaking. You should easily see the car hold pressure for a couple minutes minimum in an ideal situation, FWIW.

Hope that helps!

-Jake
 

James

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Joined
Apr 7, 2012
Messages
1,322
Location
Port richey Florida
I'm not sure about how long a car should hold the boost for but mine goes down aprox 1psi every 1-2 seconds with no leaks.
 

Xcelerate

Active member
Joined
Jun 17, 2011
Messages
43
Location
North jersey
Just to let u guys know, when u boost leak a car you have to run enough air so your boost gauge will hit more than your boost target. Let say your want 18psi of boost, then your gauge should hit over. Of you only push 20psi from the boost leak tester then you won't see 20psi by the gauge, there will be a boost drop from the turbo to the manifold. Plus you will see more leak pushing more air by the tester. There will be leaks that you won't see on lower psi. I would literally push over 60psi just to see 30psi on my boost gauge.

If you don't have anymore leaks, then go with new plugs and wires and replace all your filters including fuel filters. And make sure to gap your plugs small about .022". Good luck
 

ade

Well-known member
Joined
Aug 16, 2011
Messages
303
Location
Paumanok NY
could it be fuel cut?
 
Joined
Aug 21, 2012
Messages
11
Location
Tallmadge, Ohio
Alright... A little update, so the radiator started leaking so while I was waiting for a replacement I tore down the stock intercooler and bought my buddies 1g front mount and fabbed it up rather nicely. Ran multiple boost leak tests, several were found where the new couplers were installed, fixed those leaks and found one at the egr block off plate, fixed that one ran more tests and found a couple more at the oil cap, capped vacuum houses on the throttle body, and the the hose going into the intake for boost. Ran another test and no leaks were heard or shown with the soapy water. Took the car down the street and the problem was still present. Would pull for the first 5-8lbs of boost and when the rpms went over 3000 and the boost was held at 5 or pushed to 12 the car would blow off while throttle was still down and backfire like I was using launch control. Took it home and ran another boos leak and couldn't find anything... Changed the throttle body with one I knew worked this way I could check if it was just one of my sensors acting up however there was no change in driving with the other throttle body... I'm lost any help or ideas would be much appreciated. Thank you all who have given there thoughts already.
 

James

Well-known member
Joined
Apr 7, 2012
Messages
1,322
Location
Port richey Florida
Bad plugs, bad injectors.
 

5OF2k

Well-known member
Joined
Mar 28, 2012
Messages
664
Location
colorado springs, colorado
Are all of your vacuum lines ran properly and all of your boost solenoids/etc properly connected? Is your timing terminal grounded, by chance?
 

DynastyLCD

Well-known member
Joined
May 12, 2006
Messages
761
Location
Harwinton, CT
do you have another coil pack, or transistor to try?

ive had this issue a few times over with my cars over the years, and a few times it was the coil pack, a few times it was the transistor. check both of those for the hell of it.
 
Joined
Aug 21, 2012
Messages
11
Location
Tallmadge, Ohio
Ive tried both the coil pack and two different transistors. No change. Dumb question but which which ground is the timing terminal ground? and if that was grounded wouldn't the car idle low?
 

DynastyLCD

Well-known member
Joined
May 12, 2006
Messages
761
Location
Harwinton, CT
it would run and drive like crap, as your timing advance would be locked at 5*.

i had an issue with 73/1000 where it ran great until you built boost around 3-4k and it ended up being the Cam Angle Sensor. clearly its not the right way to fix it by continuing to throwing parts at it, but if you have another one of those to try, i suggest it.
 
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