2000 GAGT: Hesitation, High Idle, Headache.

[emmettk1]

O.K., heres the history: 2000 GAGT, 3400, we bought it used w/ about 65,000m. last August. Three days later it blew a head gasket. Used car dealership had their mechanic fix it (h/a). Around the beginning of Nov. engine was ticking, it sounded like it would be a lifter or valve. Our mechanic (who has been very good to us) said no, it was the bearing and we needed a whole new engine. He found us a used engine out of a 2003 GA(gt?), 30,000 miles with a warranty. They installed it for around 2400.00 total. There has been one consistant problem since the new engine was put in, there is a hesitation from a dead stop as soon as you give it gas. If you slowly feather into the pedal it does not do this. But if you just push right down (not flooring it, just a normal switching from brake to gas motion) it bogs right down. You can see the tach bounce down and then up. UP because it then lunges and runs incredibly. Other than the hesitation, this car screams. The mechanics have run every test known, and availabe to them. Asked everyone they know for ideas and the only thing they have found is that the hesitation is a spike in fuel pressure (too much, i forget the #'s but I rememeber it was out of the parameters) but they can't pinpoint the source. Does anyone have any ideas on that? The work they have done on this car to remedy this problem has helped some, when we first got car back w/ new engine the hesitation would occasionaly lead to a stall. Has not stalled in months, but hesitation is always there. They have put a lot of time into this car (for free) and believe me when I say my mechanics are getting just as sick of this as we are, probably moreso. The new problem is an occurance of an uncontrollable high idle. Since the engine was replaced in November it has been very cold here in Detroit, last week it got up to about 55 degrees, first time in months. When my girlfriend started it up after work the idle raced up to around 3000 rpm. She called me I told her to shut it off and restart, she did, it dropped it down to about a 2500 rpm idle. She drove it home and idled down the road at about 40 mph, having to ride the brake to go slower. She stopped to pick up our son and after restarting it ran fine. It has not been that warm since then and we have not had the problem since then. From a thread search for "high idle" the most common solution is vaccum leak. So if anyone has any ideas, I'm all ears. (well in this case eyes.)

[xeroinfinity]

Well if your fuel pressure is high your fuel pressure regulator would be bad.

Could also hav some fuel contamination or an injector problem, clogged/damaged, causing your hesitation.

Has your fuel filter been changed ??

The idle is controled by the IAC- idle air control valve. If its dirty it can stick causing high idle. The #1 vacum leak that will cause problems is the one right below the coil pack. It has a larger hose with a smaller one together, which connets to where the O2 plugs into.