GTP Fuel Pressure Regulator?

[blazeracer]

Hello all. I had a problem pop up on my 2000 GTP a few weeks ago. The car started running like crap on the freeway whenever the gas was punched. With 130k on the clock my first guess and easiest fix was to put on a new fuel filter. The problem still existed. Next, I ordered a fuel pump rebuild kit, installed it yesterday and the problem still exists. On a hunch in the back of my head, pulled the supercharger belt and problem disappeared. Car pulls hard all through the RPM's until it shifts with no misses, however, there is no boost. Put the belt back and on and pulled the fuel pressure regulator out this morning, sucked on the vacuum port and it seems to actuate. Put it back on, started the car to check vacuum, it's there and strong. Pulled the high speed relay and bent back tab 85 to put the fuel pump in high speed, let car warm up, problem still exists. Pulled the other fuel pump relay, car won't start. Put the high speed relay in the other relay slot (they're the same part #), car starts fine. This tells me the relay is fine. I don't think it's the resistor because the car won't run correctly if it's bad, and it runs and idles fine, runs great and pulls hard with the SC belt off. It only runs bad under boost, to the point where it will actually slows down on the freeway with my foot to the floor. I can go to Northern Tool and get an Actron fuel pressure test kit but it would be tough to impossible to check fuel pressure under boost as popping the throttle in the driveway spins it up way too fast. It will hit the rev limiter first. When driving it takes about a second for the problem to appear, that's when I would need to see the fuel pressure reading and have to be driving the car to do that. BTW, wife took the car to the Valvoline shop up the street the other day and the dip$hit with a GED that works there talked her into a $70 fuel injector cleaner that did absolutely nothing for it. I'm thinking replacing the fuel pressure regulator is next but there may be something else I'm missing checking out first. Searching old posts didn't turn up any info on this one. Any ideas?

Blaze

[BNaylor]

Are sure you didn't get bad gas and are you running 91 octane or better premium unleaded? Sure sounds like the ignition timing is being retarded possibly due to detonation causing KR, of course it will be most noticeable under boost conditions only.

Your problem doesn't sound like the fuel pump resistor and maybe not the fuel pressure regulator either. But you can you test the FPR at idle and at rpms below the 4K rpm cutoff by removing the vacuum line. Should have no more than 5-6 psi deviation with and without vacuum but you will need the fuel pressure tester. Another symptom of a bad FPR is taking several seconds for the engine to start. With a hose extension on an Actron fuel pressure tester gauge you can monitor fuel pressure while driving.

When was the last basic tune up like spark plugs and ignition wires? No SES/CEL light?

[blazeracer]

I've gone through about 4 tanks of 91 octane gas with this going on so it's not the gas. I can be at idle at a red light and taking off under boost and will cut out. From idle to over 5,000 RPM when it shifts with my foot to the floor and no boost it's smooth as silk. I have gotten different misfire codes since the problem started. It first read misfire on four, then random, then misfire on 6, and so on. Now that the belt it off since yesterday, no code at all. I didn't clear the code, it did it on it's own after a good haul ass down the freeway. I'm at 130k now. The motor got a full rebulid last year at 122k which included all new OEM plugs and wires from Pace Pontiac. Also, engine starts immediately with no hesitation, belt on or off. Bottom line, when boost is on, even at half throttle, the car missfires more than it fires.

[BNaylor]

Try disconnecting the MAF sensor and run it disconnected to rule it out. Since you have a history of misfire DTCs that is the direction to head and it doesn't hurt to verify fuel pressure with a gauge to rule it out as a problem. You might consider testing the CAT convertor based on your symptoms and since you had random misfire DTCs. Also you can check for a clogged/flaky CAT with an automotive vacuum gauge (0-30 in-hg).

Regardless of whether it appears to work OK with the SC belt disconnected.

[Ogre1]

Check your spark plug wires, and the plugs themselves for that matter. I had a very similar issue with a smaller pulley and factory wires. Upgraded the wires, problem solved.

[blazeracer]

Had the MAF problem before this. It got a brand new one two months ago. But I'll try it...... OK, put the belt on, unpluged the MAF and took it for a drive. Same result with addition of the 0102 code. Possible but unlikely on the cat. Had a Random Technologies high flow cat put on it a few years ago running a 3 inch straight pipe back to a custom Y-pipe running 2 1/2 after that through Flowmaster 40 series. My exhaust flows..

Pulled all 6 plugs and verified the gaps a few weeks ago when I got the misfire on 4 code. They all looked clean and in good color. I was thinking getting some aftermarket coils and wires, but I've had this car since new in Jan of 2000. Bought it with 6 miles on it. Put my mods in at around 25,000. It's been fine until two months ago. Used to take it to the friday night drags, used to run at wide open on I40 going toward Flagstaff AZ, could hit the speed limiter without even breathing hard until two months ago. The difference with and without the SC belt on is like night at day.

[BNaylor]

Any other mods that may be relevant? What brand spark plugs?

[blazeracer]

I have a pulley one size under stock (3.4"? The only one available in 2000), a CAI and the exhaust. Oh, a butt load of stereo also.. LOL.. I wonder if the supercharger itself is going south? It started a slight whine from the snout last summer, it's been working fine and the whine hasn't gotten any worse.

[BNaylor]

Umm....it sounds like a you have a good head scratcher.

On the SC pulley most likely a 3.4" but you can measure it to be sure. No re-programmed PCM module like DHP or Powertuner custom programming?

Just to be clear was the misfire on #4 consistent or now random? Did you try replacing the respective ignition wire or move the coil packs around.

The scanner being used does it read out GM extended DTCs like P1XXX and not just generic like P0XXX? The reason why I ask is I'm wondering if you have an EST/IC/Bypass control problem which would be related to the ignition control module (ICM) and/or related circuits.

Originally Posted by blazeracer

I wonder if the supercharger itself is going south? It started a slight whine from the snout last summer, it's been working fine and the whine hasn't gotten any worse.

Possible. No rattling sound like a coupler going bad? Did you check the boost control bypass valve? I get whine when boost kicks in but the snout is noise free at idle.

[blazeracer]

It's a stock PCM, in fact it's new. Was trying to track down a problem with the evap system to no avail when I put a new puter in it and it still didn't fix that problem (soleniod, pressure sensor and canister valve all check out OK). Would a stock PCM programmed to my VIN need a case read done? Well, it does the exact same thing with the original PCM if I put it back in.

I'll probably take it to the dealer and get them to scan correctly with a Tech2. My scanner is generic I guess, just does the P0XXX codes with the full descriptions. The misfires are random, the first misfire was 4, then it actually said "random", then it said 6 in the first couple of weeks, then I quit checking until today when the belt was off and the misfire was gone. I do get a code for the front O2 sensor once in a while. It will come on for a day then go away for a week. I know nothing about the EST/IC/Bypass control so I guess I'll do some reading on that since the car is gone for the day now. Wife went to work.

Oh, just clicked your time slip link.. that's sweet running a 12.6... I want to take mine down to Ennis and run it again one of these days. It's hasn't been on the strip since 2004 where it ran a respectable 14.6. Beat a stock GTP by about 5 lengths. I'm actually fixin to go back to Iraq next month and am going to completely go through the entire car when I get back. I'll be shooting for 12's then too.

Don't know how to check the boost control bypass valve.. more reading... I get the big honkin whine from the CAI when under boost, but the whine from the snout is there at idle. Yeah, I get a little rattling too like there's a BB inside there or something. Can't really tell if it's coming the case or the snout but it's been doing that since new, thought it was supposed to have a little rattle. I am getting good boost, the boost gauge pegs immediately, just don't seem to have any extra fuel accomponying the additional air.

[BNaylor]

Sounds good. At least until it is scanned with a better or high end scanner. The Tech II is still the best choice. Maybe the PCM history has some relevant extended DTCs. On any new PCM module the case learn should be run to illiminate or prevent false misfires but I doubt your original lost the settings. In the meantime I guess you can brush up on reading our old posts and keep us posted.

I bought my GTP new fully loaded back in early 1998 with about 4 miles on it and had it ever since. Over 10 years old now. Starting modding after 5 years of age. Just a toy now and I enjoy tuning it and drag racing as a hobby along with riding a MX bike. My Regal GS is my daily driver.

Iraq? Are you in the service?

[blazeracer]

I actually just got out, retired after 20 yrs. Went twice for God and country, now I'm going as a contractor for the almighty dollar.. I have a photoshop pic of what I want mine to look like after it's done. Here's a link to my GTP page.

http://www.geocities.com/blazeracer/gtp.html

[BNaylor]

Ah I see. What specific branch? I was a lifer in Army Air Defense Artillery. Just to help out a few days a week I work with the Army's Counter-Insurgency Program at Ft. Bliss where we train National Guard and Reserves (Army, Navy and Air Force) heading over to Iraq and Afghanistan. As an OPFOR. We cover ASO, Convoy Ops, Urban Ops, FOB, ROE, TCP, ECP, etc. Nice additional hobby and personal contribution to the war effort since it looks like we'll be there awhile.

Nice concept pic.

[blazeracer]

I was Army. Did the first tour in the initial invasion with 4th ID in 2003 and the second from the US Army Intel Center out of Ft. Huachuca in 2006. On this contract will be a site supervisor for 3rd country nationals pulling guard duty in the Green Zone. Should be a cush job.

My concept of the car has possibly an Otto-R body kit but will most likely have altered stock nose piece and side skirts and a rear spoiler from, dare I say.. a Honda Accord. There was a dude in Albuquerque I knew that had an Accord spoiler on his GTP done right and it looked tight. Not too over the top or anything. The real crazy stuff is underneath. I would like to attempt what Pontiac did with the original G8 in 1999. It had an LT1 with a Firebird rear subframe and an all wheel drive from an Aztec. I saw the car at the Phoenix NASCAR race and it was wicked rolling on 19's! Huge for the day.. Speaking of, the exhaust would side exit through a set of NASCAR boom tubes. At a minimum, it will get a Caddilac STS power train with a Northstar V8 and some custom made emblems where the GTP ones are now. Just cause.... Maybe like GTP-R or something unique.

Hey, If you're a 20 year retiree the company I work for is hiring. They pay $400 a day plus per diem and they ONLY hire retirees. They prefer combat arms or MP's but will take other MOS's if you were at OIF and went outside the wire. I was MI and they took me. The contract runs for 14 months, one year in country. I'll be there for four months then home for one, three times. They also match funds for both federal tax and 401k.

[BNaylor]

Very interesting. Thanks for sharing your thoughts. Other than possibly some more engine mods I really don't plan on doing much with mine. Added aftermarket 18" AR Casino wheels and Goodyear Eagle RSA tires last year. Still pristine with 95K miles.



For awhile I though you were going to mention the "B" word - Blackwater. ........ But they are not limited to hiring solely retirees. I put in over 20 years. Highest rank CWO4. Thanks for the heads up but I'll pass. I did my share of overseas tours of duty with Gulf War I and 3 years in Saudi Arabia with Raytheon. 6 years in Germany during the Cold War days. I was in Kuwait when Saddam launched the invasion. We shot down 21 of his fighter jets and 1 helicopter before having to leave and being overrun by his ground troops. That was enough for me.