vacuum leak??

[grandprixgtx00]

hey guys/girls, my SE has been acting weird for the past month or so now, and its really driving me nuts.

before i get started here, the car now has a Supercharged 3800. i did the swap last summer, and the engine has apx. 75K on it now.

when the car is idleing, the RMP's will fluctuate between 500 and 1000. once i get going, the car runs fine. i know the motor has a number of vaccum lines on the top end, and I've been checking them, but i havent found anything.

the car had new plugs/wires not too long after i put the motor in the car (had 60K on it, so apx. 15K ago) i also replaced the fuel filter, and all that good stuff.

no SES light or anything, so a scanner wont do much.

any help is appreciated! thanks again

[richtazz]

Did you put a GTP fuel pump module and PCM in it when you did the swap? The GTP's use a two-speed fuel pump with a PCM controlled resistor to vary the fuel pump speed depending on load, boost and RPM. An SE fuel pump cannot deliver the proper fuel pressure at high revs/boost, and if you didn't install a resistor with the GTP pump, you may be experiencing fuel cavitation. The GTP fuel pump at full speed will return so much fuel to the tank at idle/part throttle, it will cause a whirlpool vortex in the tank that can cause it to suck air.

[grandprixgtx00]

Originally Posted by richtazz

Did you put a GTP fuel pump module and PCM in it when you did the swap? The GTP's use a two-speed fuel pump with a PCM controlled resistor to vary the fuel pump speed depending on load, boost and RPM. An SE fuel pump cannot deliver the proper fuel pressure at high revs/boost, and if you didn't install a resistor with the GTP pump, you may be experiencing fuel cavitation. The GTP fuel pump at full speed will return so much fuel to the tank at idle/part throttle, it will cause a whirlpool vortex in the tank that can cause it to suck air.

yes, i had the PCM flashed and upgraded by ZZP, but did not change the fuel pump module. would it just all of a sudden start acting up if it was a problem w/ the module? i never had problems w/ the car untill about a month ago. i also do not experience a change in fuel mileage or anything. the car also runs just fine under boost.

i'm also wondering if maybe i should do some sort of exhaust upgrade, since the car still has just the single OEM exhaust system? this is a little side note though...haha

**edit** if this is the problem, would i need to change the whole pump??
thanks again

[richtazz]

IT may be difficult to put a GTP pump in, because your SE isn't wired for the resistor that is needed. IF the problem happened all of the sudden, I would check the TPS and MAF sensors to see if they are good. Does it sometimes start hard (long crank time), and or start then stall/stumble?

[grandprixgtx00]

nope...no problems starting besides the slow turnovers, considering the fact i still have the OEM AC Delco battery in there and the temps at night have been -15F for the past month or so.

it does seem like a MAF sensor now that you say something. since the RPM's just keep going up and down...I'm gonna try that this weekend

any other suggestions??

[BNaylor]

Before replacing the MAF sensor it is best to try a simple test first just so you don't waste any money. Just disconnect the electrical connector to it. The idle may be a little erratic until engine warmup but should stabilize. If it doesn't then it sounds like the MAF sensor. If idle is good then it is not the MAF sensor.

Also, you could be getting improper IAC counts via a bad or dirty IAC valve or a clogged port at the throttle body seat where the IAC mounts could be all carboned up.

[grandprixgtx00]

Originally Posted by BNaylor

Before replacing the MAF sensor it is best to try a simple test first just so you don't waste any money. Just disconnect the electrical connector to it.

yeah, thats what I'm gonna do...

Also, you could be getting improper IAC counts via a bad or dirty IAC valve or a clogged port at the throttle body seat where the IAC mounts could be all carboned up.

i put a MAP engineering throttle body spacer in it from 3800performance.com when i did the swap, and the throttle body seemed pretty clean when i put it in, so i dont think that could be an issue...

[BNaylor]

Did you ever remove the IAC and inspect the area where it mounts? Is the orifice clean or carbon free?

Another thing you can do is check engine vacuum and make sure it is in a range of 15-22 in-hg. All you need is a standard automotive vacuum tester (0-30 in-hg).

[grandprixgtx00]

Originally Posted by BNaylor

Did you ever remove the IAC and inspect the area where it mounts? Is the orifice clean or carbon free?

yeah, IAC seemed pretty clean. i was thinking about maybe doing a Northstar TB conversion, so a may not have to worry about it

[qoute]Another thing you can do is check engine vacuum and make sure it is in a range of 15-22 in-hg. All you need is a standard automotive vacuum tester (0-30 in-hg).[/quote]

yeah, vacuum leak is what i am leaning towards. I am going to contact my dad once he gets back from his trip to Mexico and see what he says. I'll see if he has a vacuum tester (which I'm sure he does) and see what he says about testing it for me. only thing that kinda sucks is that he lives 300 miles away from me...so I'd have to wait till next time i go up there to have it tested I'll let you guys know what happens.

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on another note...since you guys are so good w/ GP's, i am wondering what other mods i maybe should do to this car? I am not sure where i am at w/ KR, but the mods i currently have are as follows:

-gutted airbox w/ SLP cone CAI
-MAP Engineering Throttle body spacer
-ZZP 1.0 PCM
-ZZP Ubend delete w/ OEM 02 sensor put back in

not sure if i wanna go w/ the smaller pulley just yet, since i should prolly do more w/ the exhaust for support mods.

[tblake]

Originally Posted by richtazz

IT may be difficult to put a GTP pump in, because your SE isn't wired for the resistor that is needed. IF the problem happened all of the sudden, I would check the TPS and MAF sensors to see if they are good. Does it sometimes start hard (long crank time), and or start then stall/stumble?

Hey RICH, didn't the 2003 GTP's come with a different fuel pump set up/wiring? Would it be possible from him to swap in a fuel pump module from a 2003 GTP?

Just curious.....

[richtazz]

They did away with the fuel pump resistor in 01, and the fuel pump speed is controlled by the PCM on the 01-03 models. I'm not sure if the 01-03 PCM could be made to work in his year, because the 97's still used the 4T60-E transaxle that had a vacuum modulator. The 98-on models used the 4t65-E that is all electronic. As I read on, I'm shying away from the fuel pump as the cause, and looking more toward the MAF/IAC/TPS as the issue. The problem with swapped cars is that it's hard to say what was left unhooked/unplugged during the swap which could now be causing his issues. It'll be interesting to see how this pans out. Keep us informed grandprixgtx00!

[tblake]

ok, thanks for the info on the fuel pump!!

[grandprixgtx00]

Originally Posted by richtazz

Keep us informed grandprixgtx00!

will do...thanks for all the input!

now to add on...as i stated in a previous reply in here, do you guys have any suggestions for support mods? i am aiming for a 3.4 pulley, but i know i have to do something w/ the exhaust. any suggestions??

[tblake]

at the very least you have to do a u-bend delete to the exhaust. There are more supporting mods to do also. Wait for our moderators to chime in, they know thier stuff... Bob? Rich? GTPdad?

[grandprixgtx00]

well...this weekend, lets just say i was a busy guy.

i removed the TB from my car. i cleaned the MAF, TPS, and the whole TB. when i put it all back together...bam...no problems since

not sure which one did the trick. I dont think it was the IAC. the TB seemed real clean. I'm thinking that it is the MAF sensor. if the problem comes back i am just going to try replacing the MAF sensor.

i REALLY appreciate the help guys. you have no idea how much it helped out!

now onto some more mods