Sluggish miss in the lower RPMs

jusber15 · #1 10-28-2009, 09:26 PM

I have a 2005 Grand Prix GTP, supercharged 3800 with 43,000 miles. All original. I traded my 99 Regal GS with the supercharged 3800 in for this car. I've got about 4,000 miles on it since I bought it and I noticed that it didnt have the power that my Regal had. If I floored it, it would take off from a stop just fine but when it shifted into second, it just felt like it would fall flat on its face. About a week later I noticed that when the motor was cold, it would have a hesitation and a miss when taking off from a stop but went away once it warmed up. Now its missing on takeoffs just about all the time and still seems to lack overall power throughout the RPM range. I changed the air cleaner when I bought it and after reading on here, I bought some MAF sensor cleaner and cleaned that all out today with no change. I wish it would throw me a SES light, but still nothing. Got any ideas??

CrazyHorst · #2 11-02-2009, 04:42 AM

I would check easy stuff first.

Pre-number and pull all 6 plug wires off the coil packs and inspect the pack-lugs.

While you are at it, I'd also inspect the plug wires themselves. A little misrouting or a missing clip and they can chafe into each other and you lose all the spark energy that needs to goto the plug.

I would also change the fuel filter as again this falls into the "easier stuff" category.

tblake · #3 11-02-2009, 09:56 AM

But don't spend too much time looking for the fuel filter. I think in 04-05, the inline filter was phased out in the return-less type systems and now the filter is located in the fuel tank.

coolzzy · #4 11-03-2009, 12:49 AM

my 05 does the same thing, but only every 10th start or so. Stopping the car and restarting makes it go away. I too have no check engine lights and it behaves normally except for when it does this. It stutters and surges, lots of hesitation unless floored, and the MPG indicator shows very poor inst. mileage. after a restart, power comes back, is linear and inst. mileage indicator back to normal. I've seen a few posts on various forums about this, but no one has a fix. Some think its the computer causing it since a restart cures it.

I had an 02 regal that did it constantly unless i unplugged the MAF even though I had no codes (got it cheap cause i guess the previous owner coudlnt figure it out either). I replaced the MAF, O2 sensors, spark plugs, coil packs, plug wires, crank position sensor, catalytic converter, EGR valve, you name it. Spent a bunch of cash and still no change, no check engine lights either. Finally sold it and moved on, then I got my 05 GP a few years later and its happening again but thankfully only every once in a while. So long story short, don't start throwing parts at it, it may end up being a computer.

tblake · #5 11-04-2009, 08:56 PM

I think there is a GM TSB out in regards to 04+ 3800 motors and drivability issues which range from hard starts to poor accelleration, and no idle. The TSB recommends to remove the throttle body and clean it. Maybe you guys could give that a try. Just use specific t-body cleaner, and use a new gasket and you should be fine.

BNaylor · #6 11-04-2009, 09:19 PM

Quote:

Originally Posted by CrazyHorst

I would also change the fuel filter as again this falls into the "easier stuff" category.

There is no owner replaceable external fuel filter like the '97-'03 models.

We have old posts on similar issues on the '04 and up models. Do a search. Throttle body cleaning may help or there is an issue with the drive by wire system which means a trip to the GM dealership.

coolzzy · #7 11-04-2009, 10:24 PM

cleaning the throttle body will resolve the issue of starting and then immediatly dieing. I've done this and it cured that right up. Unfortuneatly it made no difference here. Again, the issue is very intermmittent, like maybe 1 out of every 10-12 starts.

tblake · #8 11-05-2009, 07:06 PM

Odd how turning it off and then back on would fix your issue. Sounds like some funky computer glitch....

roman1978 · #9 12-31-2009, 09:39 AM

I had an 05 Grand Prix GT with the same issue of hasitation at lower RPMs. Restarting the car did help but problem came back like a day or two later.I had the car at the dealer over 10 times they replaced everything from spark plugs to the computer and the issue was never resolved I had to sell the car becuse I could not take it anymore.

jusber15 · #10 12-31-2009, 11:18 AM

Well, so far I have replaced the plugs and wires and cleaned the MAF. Still no change.

CrazyHorst · #11 12-31-2009, 01:16 PM

I'd be interested to see what the A/F ratio (O2 signal) is doing during all of this....that would hint at what's going on.

Throttle response only (as in the ETC not responding appropriately) only would seem to be related to sluggish performance only.

However, I'm wondering outloud if there's a fuel system issue as that could lead to the misfiring AND lack of power....as there's no fuel filter...is this the "returnless" fuel system? A restart also causes a pressure "pulse" prior to restart. I wonder if there's a cavitation problem which is basically sending "foam" (of sorts, fewer bubbles) up into the fuel line/rail at a lower than expected pressure. Where the old returning fuel systems would have simply just purged this back to the tank, the newer systems have no choice but to push it thru the injectors. The restart could possibly allow the conditions which are causing cavitation to dissipate, settle down, and then the restart gets back to normal pressure which is enough to compress the "bubbles" into a volume where they're insignificant.

A theory at best. Fuel pressure issues normally generate zero OBD2 activity. I think if the O2 sensor voltage is being skewed down then this sensor is sensitive enough to pick up these type of problems. But you'd have to have live data feed ready and wait for the intermittent activity.

BNaylor · #12 12-31-2009, 01:29 PM

Quote:

Originally Posted by CrazyHorst

as there's no fuel filter...is this the "returnless" fuel system?

Good question. The answer is yes for all '04 and up with the SIII 3800 and 5.3L V8.

In addition with a scan tool that has the capability I'd check the short and long term fuel trims and the misfire counters for each cylinder. Also, I would not rule out a secondary ignition issue such as the coil packs. Swap them out with a known good one or around just to rule it out. Plus you can check primary and secondary coil resistance with a multimeter (DMM).

POST REPLY TO THIS THREAD