misfire/sputter/bog

[RobGTP]

I have a 2000 grand prix gtp, with a cone filter on a pvc pipe haha, speed daddy headers, no cat, no res, new plugs (ACD) and new wires, the coils might be oldish, also O2 simlulator when i get on the gas it starts to bog sorta like wen the cat went bad but not quite that severe, it bogs wen it reaches higher rpm's, but if you drive it easier it drives completely normal, smooth and perfect, does it need to be tuned, could i get a 3800performance or overkill pcm? or the coil packs replaced? idrk it seems like it always has a misfire problem no matter what its pissing me off now. any thoughts would be cool, (fuel pressure regulator is new too and fuel filter) its got 172k

[Slick2500]

Misfires can be caused by many things on these engines.

• Faulty spark plugs or wires
• Faulty coil (pack)
• Faulty oxygen sensor(s)
• Faulty fuel injector(s)
• Burned exhaust valve
• Faulty catalytic converter(s)
• Stuck/blocked EGR valve / passages
• Faulty camshaft position sensor
• Defective computer

You said you already replaced plugs, wires and removed the cat so that eliminates those. Is the misfire on one cylinder or do you have code P0300?

[RobGTP]

its not throwing any codes right now, probbaly because i drive it normally since it runs like **** at high rpm's

[agentbluescreen]

First thing to check is for iron brake rotor filings stuck on the center magnet of the Crankshaft Position Sensor, these cannot only eventually disable the tach and/or complete ignition timing, fuel regulation and injection timebase, longer metal filings stuck there can completely screw up the virtual spark advance/retard operation. Also check that nobody has bypassed the fuel pump resistor, as chronic (rich) fuel overpressure will also give exactly these sorts of symptoms.

BTW a $2.00 12VDC 75Watt MR16 quartz halogen track lighting bulb is the best replacement for the not so cheap huge $30-40 TRW ceramic encased fuel pump resistor/fuse thingy that so often blows out leaving you stranded on the highway when the fuel pump hits a rock of crap in the gas tank pickup line at low pressure.

Seems GM neglected to use a durable DALE-type high power heat sinked power resistor with a secondary 8 amp fuse for safe low power fuel pump operation, electing to use the (now unreliable) resistor itself as the "secondary" low-voltage operation "fuse".

A sealed 12v quartz halogen bulb just goes full brightness whenever/if ever the fuel pump motor stalls at low speed, and restarting the engine will clear the blockage with full power to the pump motor. (it also doubles as a nice fairly useful engine compartment light that informs you of valid low fuel pressure pumping mode) When the quartz halogen is functioning in resistor (low fuel pump power) mode it simply, slowly, glows-up to cool soft yellow and cherry red, (10 watt brightness) rather than fully incandescing, and it also has much higher cold resistance giving a more graceful fuel pressure drop which the mechanical vacuum fuel pressure regulator handles more gracefully.

It also provides for a bit lower than stock low-fuel-pressures, meaning more accurate injection/cutoff, broader trim control range and better mileage.

Unlike the undependable original TRW potted-ceramic resistor-fuse thingy, the 75 Watt bulb will last you indefinitely (at 10 Watts), can be found in most dollar stores and only costs you $2 to replace. If it ever goes on you, you can get the engine going again with a single wire twist-tie...

[FordMan77]

Get it scanned and see if any codes show up. It's bogging when you get into boost. Could be a number of things. Also, check for vac leaks around every fitting, especially the vac T under the SC snout as it likes to crack there. Not sure about running no cat w/o a tune.

Never seen a CKPS cause bogging w/o other symptoms.

If you decide to replace the coils then make sure you go with stock ones. MSD and the like usually aren't the best for our cars.