Flutter in idle; serious hesitation

[comanche]

99' Olds Alero 3.4L
(engine recently replaced, sold as 22k)

Idle when started flutters about 500 rpm back and forth 3-4 times.
Severe hesitation on acceleration (not all the time, usually after a couple minutes driving and most often after turning a corner)
New plugs, plug wires, fuel filter, air filter (also tried WAI)
Different EGR valve, MAP sensor, ignition module
Fuel injector cleaner run through multiple times
Vaccum lines checked, electrical connections cleaned.

Hesitation so severe at times it can be unsafe when trying to turn in front of oncoming traffic. Any ideas??

[cavaliers60]

you might have water leaking in somewhere.... I know my car did stuff like that when I got water IN the engine a couple times... Thank God it didn't hurt it... But yeah, sounds like something's leaking.... Might be a LIMG thing gone unfixed...

[SweetNLow]

o2 sensor

[antichrysler]

^ agreed.

Wouldn't hurt to try some condensation remover either in the gas tank.

[Cliff8928]

Were the old fuel injectors re-installed back onto the new engine?

[comanche]

Yeah, old fuel injecters were reinstalled. (the engine was a 00' so I had to switch out the injectors and harness.)

Which 02 sensor?

[Redog]

Most likey a downstream, but replacing both wouldn't hurt

Is the MAP plugged in all the way

[Gr1m]

get a voltmeter and check the o2 sensor pigtail after uve replaced it

[comanche]

MAP appears to be plugged in fully - Why? (The connector tab broke, but i taped the plugs together really good.
What exactly am I looking for on the voltmeter?

[jackal2000]

scan it for codes, not all codes set a MIL. i would clean the throttle body and change the tps too.

[jackal2000]

Most likey a downstream, but replacing both wouldn't hurt

no way is it the downstream sensor because all that sensor does is check to make sure the cat converter is working. that being said, if this problem is caused by an o2 then its the upstream one. they run about $85.

[comanche]

Took it to the dealer, talked to a friendly tech:
Test-drove it with the tech2, he said start with the MAF sensor, also clean the IAC.
Replaced the MAF with a rebuilt one, cleaned the IAC = no bouncy idle yet, but the hesitation is still the same.
He said it looked like the 02 sensor was good, & doing what it was supposed to.
It didn't cost anything at the dealer, but $106 w/tax for the unneccessary MAF kinda' hurts.

[comanche]

I did also put in a bottle of gasline antifreeze.

[Redog]

MAP appears to be plugged in fully - Why? (The connector tab broke, but i taped the plugs together really good.
What exactly am I looking for on the voltmeter?

I left mine unpluged once by accident and the car was revving from 500 to 1200 at idle

[Gr1m]

IAT sensor/pigtail...the car isnt throwing any codes?

[Jferg2223]

when my limg went it started doing that until the car got warm

[comanche]

This car only does once warmed up about 3-4 minutes.

At least the idle is fine now (so far) - replaced IAC sensor.

The only code is the system rich code.

[Jferg2223]

This car only does once warmed up about 3-4 minutes.

At least the idle is fine now (so far) - replaced IAC sensor.

The only code is the system rich code.

sounds like maf i think you mentioned a "rebuilt one" being put on if im not mistaken but thats the problem

[comanche]

Well, it looks like the LIM gasket is leaking. I'll start with that and see if the issue resolves itself.

[comanche]

LIM gasket replaced, same old problem just as bad!

[Ryan from Ohio]

I gotta ask since I didnt see it...

Fuel pressure @ the rail. Hit the valve and let the gas fly. Maybe you got air in there???

What about the temperature sensor? The one before the TB people "chip" with a resistor... Also TPS.

[comanche]

TPS replaced w/used.

No idea on fuel pressure - probably should check that, not sure exactly how...

Temperature sensor believed good... no idea.

[Ryan from Ohio]

Put it in run dont start.

Remove plastic cap on the fuel rail use small screwdriver to derpress valve. It should shoot right out of there.

Im not sure if there is a bleeder of any sorts. I git mine up every time the fuels been disconnected just in case.

[comanche]

For those who had input, the problem seems to be fixed. The GM dealer did a MAF relearn and that did the trick.