2g bogs under boost

[Lucas03es]

Okay, I have a bone stock 99 GST with the only mods are a walbro 255 (old fuel pump was bad) a new radiator, and an exhaust. I just did the head gasket 133 miles ago. The HG was bad, so I swapped it, drove for a hundred miles or so on it and then finally I wanted to see what the car has. As soon as it starts to spool, the car bogs a bit, but then picks up but nothing like it should be. I figured it was a boost leak, so I tested it and the port on the turbo that goes to the WGA didnt have a hose on it, so I put it there. nothing happened still does it. I hooked the tester back up, and coolant starts to come out of the radiator hose? I just changed the HG wtf is that something bad again? I just deleted all but the necessary vacuum lines and it is still doing it! Any ideas on this? Thanks!

 

[dsmspoolin]

You might be over running your stock fpr with the 255 fp.

 

[kimcheefists]

Do you have a fuel pressure regulator to compensate for the 255 fuel pump?

 

[tenaciousd199]

No fuel pressure regulator

 

[Lucas03es]

There is no fpr, but my galant has a 255 and no fpr, and it does not bog down like that. Is there any way to make it not do so without putting in another fuel pump?

 

[kimcheefists]

I bet if that Galant has a wideband, it'd tell you you're running rich. The only fix is to get a fuel pressure regulator or ≤190 fuel pump.

 

[Lucas03es]

My galant does have a wideband and it sits between 14.6-15.0 at idle. Could it be because the galant has 510cc injectors with a 2g MAS and an SAFC, and the gst is stock? I just want to get this problem fixed asap if possible.

 

[tenaciousd199]

I bet if that Galant has a wideband, it'd tell you you're running rich. The only fix is to get a fuel pressure regulator or ≤190 fuel pump.

Don't worry about the galant...

 

[kimcheefists]

Since you have a 255 pump and nothing to compensate for that extra pressure, you're most likely running rich. The only quick fix would be to get a ≤190 pump from, say, a junkyard.

 

[Lucas03es]

Ill see what I can come up with. Ill see if I have another SAFC laying around I can put in it or find a different pump. Thanks.

 

[staztrx250]

the safc wont do it because the stock injectors are probably getting over run. I would try replacing your stock fpr with a new one or an evo one. The stock fpr can get weak over time. if that doesn't work switch to an AFPR.

 

[Dert]

FPR is usually required with a 255, bad plugs, wires may be also contributing

 

[99gst214]

the safc wont do it because the stock injectors are probably getting over run.

Yes, the safc is useless. You could try to adjust the fuel curve all day long, but the fuel will just keep coming. Get a AFPR!

 

[Lucas03es]

Ill see what I can d about getting a fuel pressure regulator. The plugs are new and properly gapped Denso's, and the wires are relatively new also.

 

[Lucas03es]

I just put in a good working OEM fuel pump, and the car is still doing this. I had the window down, and while the stuttering is happening, I can hear air coming from the drivers side that sounds like an exhaust leak. Could an exhaust leak cause this? What are the most common exhaust leak areas? Thanks again!

 

[Nati0nalxCrisis]

Could be a boost leak then.

 

[Lucas03es]

I checked for a boost leak and I wasn't getting anything

 

[Nati0nalxCrisis]

Hmm I don't see why an exhaust leak would cause it to only give 5 pounds, unless its pretty major.

Your expanding theory might have something to do with it, maybe an exhaust leak, when your car is cold a crack wouldn't be very big but when hot it widens possibly?

 

[ThomasG-1b]

Wait now. How much air were you putting in? Cause you said there is coolant coming out from the coolant hose. What one? Turbo lines? If your getting air in the coolant the hg is bad.

 

[Nati0nalxCrisis]

Thats not always necessarily true. You can have air in your coolant lines without having a blown HG

 

[Lucas03es]

I think I was putting in too much air, and it may have pushed a little coolant. I think its an exhaust leak because I can hear the air coming out and I can smell it also. I just picked up a new exhaust manifold gasket for it and I may get to it tonight - I'll let you guys know.

 

[JEFFREYCASTGSX]

Do another boost leak test, again, and re-check plugs to be sure they are the CORRECT for the application, the usual for our cars is the NGK BPR7's(our cars are tempermental with other plugs), and make sure they are a proper gap(around .28). Can you datalog?

The fuel pump has nothing to do with this problem, that big of a pump SOMETIMES cause the FPR to be overrun(and is more present in 2g's than 1g's) and cause sudden/intermittent rich conditions that is usually present at idle/cruise only, at wot the FPR is usually able to control the fuel pressure.

 

[Lucas03es]

That is the correct plugs that I have in the car properly gapped. I do not have a datalogger. I will be doing another boost leak test once I get a chance to swap that exhaust manifold gasket so maybe tonight if I have time.

 

[Lucas03es]

So I replaced the exhaust manifold gasket with a composite one (there was a two layer metal one on there? Is that stock?) that I also sprayed with copper spray. The car does build boost a bit but then starts to bog down again. While separating the turbo and the manifold to check out that gasket I broke the stud, so I have to get that fixed first before I can redo a boost leak test. Does anyone have any ideas of ### else could possibly cause this? I am very sick of this problem! Thanks!

 

[dsmkidd20]

my car bogs between 0 and 5psi but fine past that. any reasons why?