ORIGINAL: Pson

Ok I have a 99 2.8L V6, auto tranny FWD (75,XXX miles). Now here is the thing I have had a rough idle for awhile now and a fulttering feeling when hitting the gas hard (around the 2,500 to 3,500 rpm) So hmm I was thinking motor mounts...changed them and the tranny mounts too. Still the same problem rough idle..so I drove it around and well it seems only to happen when its idling (800 rpms)(happens in the AM after the SAIP turns off)or hard on the gas (in just about everygear during the rpm range listed above) So start the car rough idle in (P)I put the car in(D) and bam rough idle, put the car in(R) and bam rough idle...put the car in N and smooth idle????? So I drive and it happens while driving I put it in (N) while driving and its still there going up or down a hill...still that fluttering during those rpm ranges. So I play around with the wheels and bam TRE's shot..I swap them get the alignment and most of the fluttering is gone...but its still there???? and the rough idle is still there too. Now I am just lost and pissed off now at my ride.Last night I am sitting at the light on an off ramp and the car started jumping or spiking the rpms??? I am lost and don't know what to do at this point so that is why I called for the masters to help me with this iusse...below is all the work I have done to the car in one year

Bilstiens shocks and H&R springs (60,000 miles)
Two new CV alxes (60,000 miles)
Timing belt, all gaskets, snub mount(68,000 miles)
PCV hose (60,000 miles)
New tranny filter and gasket, along with flush (mobil one ATF) (65,000 miles)
2 motormounts (75,000 miles)
2 tranny mounts (75,000 miles)
2 new TRE's (75,000 miles)
New spark plugs (65,000 miles)
Cleaned the TB (75,000 miles)

I am thinking ether coil pack or spark plug wires or even Tranny (which I don't know how for it happens while in Park and in N now??)

So what do you guys think about this problem?? I have dumped well over 3 grand in the POS in one year and it still can drive smooth hell a chevy rides better then this car now?

ORIGINAL: acetrebo

Have the codes read and see what comes up.

Sounds to me like you have a misfire. Its more evident at idle, and in nuetral the car idles higher than in drive, so thats probaly why its seems better.

Codes will tell you which cylinder(s) its in. Possible causes are Ignition control module, coil packs, spark plugs (you said you changed), among other things. The codes will help eliminate a lot of guess work and will set you on the correct troubleshooting path.

ORIGINAL: bentframe

you have inner and outer TREs. if the outers were bad and you drove on them for a while, chances are the inners are bad now too

ORIGINAL: acetrebo

Hmmm, no codes at all. Strange. What you describe definitely sounds like a misfire.

So, before going any furthur, try this: First, disconnect the negative battery cable for a few minutes (make sure you have your radio code). This will reset the ECU, possibly helping your car adjust better the idle.

Then, after reconnecting the battery, do a throttle body alignment, by turning the key to the on position, but not starting the car, and leaving it alone for about 1-2 minutes. Do not touch the gas pedal during this time. This resets the throttle linkage and body.

Then go for a good 5-10 mile drive, and see if any of this helps.

If that does not do anything, the next thing I would do is start pulling coilpacks cylinder by cylinder, to see if you can find a bad one. If you pull one out, and there is no change in the engine idle/roughness, then that pack may be bad.

Then, if it still continues, maybe try to read the codes again after some driving, and see if anything shows up now.

Good luck.