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Old 08-09-2012   #1
the Uub
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Phantom Running Issue

I am having an issue on my 88 tpi 350 GTA. I almost always have the hard start/extended crank issue, but sometimes when I fire it up the idle goes between 500-1500 RPM and I can hear the fuel pump whirring in the back in time to the revs. I was having an issue when I pressed the gas real hard it would get to 3000-3500 and act like it hit a rev limiter. Replace d the MAM and that went away. Still having the hard start and intermittent idle issue. When that issue happens it does not matter if I try to drive or not, the revs still change and the fuel pump still changes pitch. I checked the fuel pressure, it was 40-41 PSI. I don't believe timing is an issue because I can drive for 3 weeks without any issues except for the hard start. If I drive my other vehicle for a few days and get back to the GTA, the problem magically fixes itself.
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Old 08-09-2012   #2
MunsonGTA
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GTA Year: 1987
GTA Engine: Custom
Re: Phantom Running Issue

well what is the info on your car? is it all stock? any mods? have you done anything to it recently?
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 08-10-2012   #3
merc3065
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Re: Phantom Running Issue

88's have hard start by default. The crank timing will allow for 3-4 complete revs of the motor before it starts to prime the engine's oil system and work up the fuel/air mixture for cold start. It's in the computer code. I modified my PROM to start .5s vs 3-4 seconds after the key was turned as I got tired of waiting for the engine to turn over and over before starting.

The idle problem...could be any number of things. Would need to see what the Idle Air Control motor is doing and what the computer is requesting in way of desired RPM.
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Old 08-11-2012   #4
YumikoGTA
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Re: Phantom Running Issue

Well I am unsure if your GTA has the cold start valve like the 1987 GTAs do, but when these engines are first started, it is normal for the rpms of the engine to go up to 1500 rpms right at first and after a few moments it then is supposed to slowly go to around 700 rpms. This is because the cold start valve is working and it puts more fuel into the engine when it is cold. From what I understand about it, the cold start valve functions on the fuel injection engines like a choke on the carborated engines does.

As I remember, once in the beginning of the 1990s, I brought my GTA to the Pontiac dealership for some engine maintenance. I was standing next to my GTA and one of the mechanics was sitting in it to drive it into the garage there. There were two other mechanics standing next to me. When he turned on my GTA, the mechanic inside my GTA commented to the other guys about how it was working properly how the rpms first went to around 1200 and then slowly the engine rpms went to around 700 rpm. He asked them if they noticed it and they asked why it did that and he explained it to them. I listened to what he was saying and that is how I first learned about it.

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Last edited by YumikoGTA; 08-11-2012 at 01:46 AM.
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Old 08-11-2012   #5
red88tagta
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Re: Phantom Running Issue

I have a stock 1988 GTA 305 engine. Starts everytime within 1 second even after sitting for weeks. I cannot hear the fuel pump running. May have been replaced by a P/O. The only problem similar to yours was the idle issue and a 33 cel code. MAF sensor which after sorting it out was the ecm not energizing the MAF burn off relay. I would start with do you have any codes? Second, Replace the fuel pump second. Third, is there something in the fuel tank that could be blocking the intake of the fuel pump intermittantly?
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Old 11-19-2012   #6
the Uub
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Re: Phantom Running Issue

Well, I found out the issue, after troubleshooting, (clamping off the fuel pressure and return lines with injector charged,) found that the check valve in the fuel pump is faulty, it allows fuel to leak back down when the pump is not running. Need to replace the fuel pump, any suggestions on brand? I was thinking Denso or Delco as an OE replacement part, but considering a Walboro 255lph pump as a performance upgrade.
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Old 11-19-2012   #7
MunsonGTA
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GTA Year: 1987
GTA Engine: Custom
Re: Phantom Running Issue

I did the walbro 255 upgrade on my car, very happy with it.
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 11-19-2012   #8
prokilllsx
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Re: Phantom Running Issue

What are your expectations for future performance upgrades, or goals?
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Old 11-22-2012   #9
89-5.7GTA
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GTA Year: 1989
GTA Engine: 350 TPI Automatic
Re: Phantom Running Issue

I used a Bosch unit from Rockauto.com. I don't plan any engine mods, except possible bolt on. The car now runs better than ever.

What is your fuel pressure? After my car sits for a while it bleeds down to zero, but instantly comes up with ignition switched on. From your description, do you mean that the faulty check valve allows the fuel to leak back, out of the fuel rails? I assume that the check valve is not intended to hold pressure when the car is not running, but keeps the fuel in the rails and injectors? Did I ask that question right?
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Old 11-22-2012   #10
MunsonGTA
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GTA Year: 1987
GTA Engine: Custom
Re: Phantom Running Issue

Eventually the system bleeds off all pressure, it happens even with the stock setup. It takes a couple of hours but it bleeds off on my gauge mounted to my fuel rails. I have never seen a setup that doesn't bleed off pressure.
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 11-22-2012   #11
prokilllsx
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Re: Phantom Running Issue

It seems like I've heard that the fuel pressure regulator can go bad and cause pressure issues and bleed off. Might be worth looking into.
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http://prokillcincy.com/ LS1/4l60e, 3,200 Edge stall, 9 bolt w 3.91's
445 rwhp 381 tq. 11.20 @ 121, 7.15 @ 96mph 1/8 mile w/ 1.55 60 ft. New times coming soon.
http://www.youtube.com/watch?v=PrFkd1XxrEw
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Old 03-20-2013   #12
the Uub
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Re: Phantom Running Issue

Sorry I haven't been on in a while Tony. I wound up replacing it with a Delphi. Fuel pressure is spot on at about 44PSI, and yes, the purpose of that check valve is to keep fuel pressure in the rails and at the injectors eliminating an extended crank time while the fuel pump primes the system. When I changed my pump out the exhaust was missing and I was able to let the suspension from the car due to the style of lift I was able to use. I still had to remove the panhard bars though. Somebody told me that if I wasn't careful that the rear could shift while the panhard bars were out and the suspension was hanging. I was fortunate and everything worked out and bolted back up smoothly.
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