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2000 GTP issues...

B

Blazeracer

New member
I have a 2000 GTP I've owned since new. Recently it started acting up under boost. When the motor is cold it runs like a scalded dog. Once it warms up it about loses all power. Ran a scan with HP Tuners today and getting a couple of codes here. 0300 for Engine Misfire and 0171 for Lean Bank 1.

Hooked a vacuum gauge up and all hoses are pulling 19 inches of vacuum. Fuel pressure is around 40-41 at idle and in the neighborhood of 50 or more at RPM.

When it start spitting in popping I'm also getting knock retard out the waa-zoo. If I take the blower belt off it seems to run good, of course with no power. Never did a scan with no blower belt.

Here's an HP Tuners snapshot at WOT. TPS is at 100%, rpm at a measly 3,976, MAP is reading 164, MAF is 23 lbs/min, injector pulse width for boat banks is at 17.9, timing advance is at 4.5 with KR at 6 peaking as high as 9. LTFT is at 7 and STFT is at zero. Looking at the LTFT and STFT histograms after the scan they are both trying to add fuel like crazy.

And, the laptop just went dead... So any ideas. I was leaning toward the fuel pressure regulator but not to sure now. Is there something on the charger that adds fuel when under boost? I'm leaning toward a lean condition, but haven't a clue on the cause.
 


what kind of miles? clogged cat maybe?

does the cel light flashing when your flooring it? clogged cat, or the need for a tune up real bad will also do that.
 
Like I said, with the supercharger belt off it runs great. It will tach out way past 5 grand. When it's cold too, it screams. Will break the tires loose at 20 mph with TC off.
 
try moving the vac lines around and then spraying some carb cleaner at the vac line ends while its running. if the idle jumps up, you found a vac leak.
 
Carb cleaner not needed. I ran and actual vacuum gauge all the way through. Got 19 inches from front to back on the vacuum system. Carb cleaner's the shade tree way.

There is a gizmo that is between the FPR (which gets vacuum from the manifold) and the actuator for something on the inlet of the supercharger (probably to allow vacuum when the charger is under boost). That little gizmo connects the two sources of vacuum, the inlet of the charger and the manifold. When under boost the line out of the rear of the supercharger is under 5psi pressure, cause it's in boost. Just verified it with a guage. The one on the charger inlet is still under vacuum, again verified with a gauge.

Should the manifold vacuum port have a one way valve that will only allow vacumm and not pressure on it? That would seem logical. Hard to run vacuum stuff under pressure. I might try a bypass for the FPR and see what that does.
 


ADD, the little gizmo I'm talking about doesn't seem to do anything. No vacuum passes through it either way, on the throttle or off the throttle. It has an electrical connection on it. The other thing with the actuator on it is the boost bypass valve I guess.
 
what im saying is test the vac lines any way with carb cleaner while moving them up and down or wiggling them, as the ends crack. sitting still at idle the leak can hide, move the lines, and bam, leak area shows up. spray he solenoids also. anything a vac line plugs into.

theres no one way valves in the vac lines. on the boost solenoid there should be one open vac port, its supposed to have a little foam filter on it, but they fall off.
 
Ok. it has the open port with the little piece of foam on it but the foam is sideways and not covering the port. Read this trick on another thread and will try it on my way home.

"I ran across a thread where a wise person told the questioner to remove the vacuum hose between the BCS and FPR and run the hose JUST from the FPR to the snout and then unplug the BCS(electrical connection). READ post number 16 http://www.grandprixforums.net/booooost-68178.html (booooost)"
 
that to bypass it, if it works unplugged, from the harness and the vac line the boost solenoid is bad.

you can just pull the vac line off it, and jam a golf Tee or stick in the line to cap it. watch the line end, well check it for cracks when you take it off, they get real hard, and brittle and snap when pulled off over the hump on the vac port.

a 2 inch new piece of vac line will replace the factory end, just use a razor to cut it off the plastic line. most auto parts stores will not charge you for 2 inches of vac line, so just ask for it. stuff is cheap, cents per foot. maybe 10 cents if they charge you?
 
Didn't work, and with moving stuff around vac lines busted all over the place. NOW it's hard to start and runs bad. Gonna buy about 6 feet and replace all the little skinny plastic vacuum lines and go from there. How hard it was to start today, I'm suspecting fuel pump. I can't see pressure with the motor under load going down the road. I put an LS1 in my 70's jet boat last winter. It was acting similar to this the couple of times in the water. Run great on first start up then run like crap. Fuel pump fixed it.
 


advance auto sells these little white T's for the vac line, like 2 bucks for a pack of 2, its all you need for t's. ive yet to find anything as good anywhere else. as far as T's go.

you need to replace the T on the fpr, and under the snout.

heres a pic of the T's i used and vac line.

limjob11.jpg
 
I think I replaced the fuel pump about 5 or 6 years ago and was in a bind at the time, pretty sure it's an Ebay china pump. Already bought T's and fittings. We have O'rielly's here in Texas.
 
O'rielly's is the only parts store i dont have here lol, i got every other one under the sun it seems. all within 10 miles of me.
 


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