Breaking up at lower rpms

[JMoraru]

I'm pretty sure this is spark plug related, but I figured I'd get some other options before I start ordering replacements. My car is a 2007 GT with a Paxton Novi 2200, KB boost-a-pump, HT0 plugs, whatever injectors come with the kit (forgot the lbs - the blue ones), long tubes, etc. Car has 93k miles, has been boosted since about 30k miles. I last replaced the plugs at 71k miles - I forget the exact gap, but I checked them all before putting them in.

I feel like the drivability as a whole has been a little off recently, especially at lower RPMS. Within a few minutes after starting, it sometimes seems like the car is missing at low RPMs and then I finally get ignition at some point. It seems to get better once the car is warmed up. Even in parking lots or leaving a light it seems to be slightly more inclined to bog or want to die. It still pulls pretty good through the power band, but might be a little down on power (or I just crave more power).

As I type this I realize I'm probably due for a fuel filter change - could that be part of it?

Could the ignition coils themselves have something to do with it?

 

[redfirepearlgt]

May be time to check for vacuum leaks. I assume you aren't running cams so vacuum at idle on the car should be at 15" or higher in number. Another indication of this may be a slightly higher idle (If you don't have a vacuum boost gauge now is a good time to get one. It is a great asset). That be the case there are several methods to find the leak source. Propane tanks, TB or Brake cleaner can be used, anything that can be ingested through a leak that will change the burn causing the engine to either surge or struggle will work. I personally use a propane torch with the valve cracked slightly.

A clogged or slow fuel filter would likely cause cut out up higher as demand for fuel increases.

COP boots can cause issues if they have developed pinholes allowing the spark to arc to the head but that would likely be felt throughout the RPM range.

You could try pulling the plugs and read them to see if there is indication of a clogged or improperly atomizing fuel injector as well. Refer to the spark plug manufacturer website. Most have cards for reading the spark plugs to determine rich or lean; hot or cold; etc. If the injector is partly clogged it may not properly spray the fuel into the mix at lower demand but do so as demand (more throttle) increases.

Hope this helps.

 

[46addict]

Might be due for a throttle body cleaning.

 

[01yellerCobra]

22K is a little much for plugs in a boosted set up IMO. I usually change them around 10k. I'd pull the plugs and check them out. And look over the COP boots while you're there.

 

[truckman7]

Is the cel light on? Throwing codes? 1st might be dumb but check fuel reset button in ds kick panel. Get rid of the bap and get gt500 fuel pump. Those bap like mine were notorious for leaking and blowing off. Put comp on it and check the pids for fuel trims and pressure. Get a retune/dyno.


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[JMoraru]

Is the cel light on? Throwing codes? 1st might be dumb but check fuel reset button in ds kick panel. Get rid of the bap and get gt500 fuel pump. Those bap like mine were notorious for leaking and blowing off. Put comp on it and check the pids for fuel trims and pressure. Get a retune/dyno.


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No lights or codes. I have the Kenne Bell BAP, not the one that comes with the Paxton kit.

I'll pull the plugs and do come checking/cleaning this weekend. Thanks everyone for the input.

 

[01yellerCobra]

Is the cel light on? Throwing codes? 1st might be dumb but check fuel reset button in ds kick panel. Get rid of the bap and get gt500 fuel pump. Those bap like mine were notorious for leaking and blowing off. Put comp on it and check the pids for fuel trims and pressure. Get a retune/dyno.


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If the button was popped the car wouldn't run at all. No fuel=no start. How did your BAP leak? It's an electronic part.

 

[truckman7]

The clear corrugated line that comes with the kit would crack. Replaced it with rubber fuel line. For whatever reason if mine popped it would cut down on the fuel and the wrench light would be lit. Would be enough to start it and idle but nothing else. If I'd give it gas it would fall on its face.


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[01yellerCobra]

The clear corrugated line that comes with the kit would crack. Replaced it with rubber fuel line. For whatever reason if mine popped it would cut down on the fuel and the wrench light would be lit. Would be enough to start it and idle but nothing else. If I'd give it gas it would fall on its face.


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Are you talking about the line for the Hobbs switch? I can see how that would affect things if the BAP doesn't know when step up the voltage. I think that's why most people run them 100% all the time. Personally I'm not a fan of the BAP. I'd rather run larger pumps.

 

[truckman7]

Im not a fan of the bap at all. I couldn't tell u how many times I pulled out that back seat while on the street to fix that damn thing. Just went with the bigger pump and never looked back.


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[BruceH]

22K is a little much for plugs in a boosted set up IMO. I usually change them around 10k. I'd pull the plugs and check them out. And look over the COP boots while you're there.

Same here. On a boosted setup I always changed plugs every year or 10k, whichever was sooner. Boost is hard on plugs.