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Hello, i have a 2004 PT Cruiser GT Turbo 5-speed with a AGP stage 2 waste gate, 3" O2 housing and 3" cat-less down pipe, intake, HKS bov with block off plate and a Diablo Sport Intune on the 91 tune. It seemed fine for the first few months (ran 14.1 @ 101mph bogging off the line) and AFR's were about 11.2 maximum. Now even when i add as much fuel as the Diablo sport allows (i think it's like 40%) it starts fine ( >10.0 AFR ) then as it starts to go up in the RPM's, maybe around 4000rpm it will go to 12.5 AFR or 12.8 then i can feel it getting slower and i can see the boost drop from 17psi to about 12psi. I can also hear the waste gate sound changing. Last time i did a data log it showed 3.5 knock retard i think but it's probably worse now since back then it was only at 12.0 AFR. I was reading an old post on here and one guy had a similar problem and he fixed it by getting bigger injectors. Does any one have any ideas of what it could be? maybe a weak pump?



I've had the car for over a year and it's been great but i did only pay $500 for it since it needed a clutch slave cylinder. I originally bought it for an SRT swap for one of my 1st gen Dodge Neons but it was in great shape so i decided to start modifying it instead. I was gonna post on a PT forum but i feel like i'd get a better answer here. I do have an extra set of SRT-4 Injectors that i'm gonna try, hopefully that fixes it
 

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How many miles on your PT? Check fuel pressure, and boost leak test the car. Has the weather gotten cooler where you are at from when it was 11.2 AFR at WOT? KR and a LEAN AFR is not a good combo at all.
 

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If you had just a boost leak from somewhere in the intake tract, I'd normally expect the car to run as rich or richer. It is normal as the engine rpms increase for boost to drop but if you were holding decent air/fuel ratios before and now are going lean into high 12:1 range and getting knock, I'd second the suggestion to check fuel pressure. If the pump is weak and pressure is dropping as demand increase (from running more duty cycle, which keeps them open longer at higher rpms) it could cause those symptoms.

Since you have an inTune you could also try to data log all the sensor data, specifically the manifold absolute pressure (MAP) to see if it's off. That along with rpms, the intake air temp (IAT) and pre-programmed tables determine how much fueling the computer is commanding. You could also take a look at injector duty cycle and the short and long-term fuel trims (STFT/LTFT; adjustments the computer makes when it determines it needs to add or remove fueling over what it calculates should be needed). If the trim values show the computer is trying to also add more fuel that might further indicate a pressure problem.
 

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Great advice as usual^^^^

I didn't mean to correlate a boost leak with running leaner. It was just a statement that he probably needs to have it done AND check the fuel pressure. So many owners never boost leak their car and are losing out power
 

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Sorry for taking so long, it's been raining a lot and i've been busy.

Try the injectors and let us know,but are you sure you do not have a leak?
The Fuel rail on my PT had no schrader valve to test the fuel pressure but i had a spare 2003 fuel rail that has the valve but it had the pink injectors. I swapped the injectors to some 2004 SRT-4 injectors. Still the same problem with the different injectors but now it the AFR's start at 10.0 then spike to 11.7-12.0 so it seems to have helped a bit maybe. I ordered a fuel pressure tester on Amazon and just received it so i haven't had a chance to try it out yet.

How many miles on your PT? Check fuel pressure, and boost leak test the car. Has the weather gotten cooler where you are at from when it was 11.2 AFR at WOT? KR and a LEAN AFR is not a good combo at all.
About 188'000 kms (116'818 miles) on it and last time i did a boost leak test was last year and i installed a used HKS bov since then. I'll do a boost leak test and fuel pressure test as soon as possible and yes it has gotten colder out, I live in New Brunswick Canada. It was about 28C (83F) when i raced it at the track and now its about 12C (53F)

Since you have an inTune you could also try to data log all the sensor data, specifically the manifold absolute pressure (MAP) to see if it's off. That along with rpms, the intake air temp (IAT) and pre-programmed tables determine how much fueling the computer is commanding. You could also take a look at injector duty cycle and the short and long-term fuel trims (STFT/LTFT; adjustments the computer makes when it determines it needs to add or remove fueling over what it calculates should be needed). If the trim values show the computer is trying to also add more fuel that might further indicate a pressure problem.
I have a feeling it's the fuel pump. I've only tried data logging once since i'm not familiar with it at all, but i'll try to figure it out a bit more and i will post it on here. Also, i forgot to mention that i put on a brand new mopar map sensor and i run 1 step colder NGK iridium plugs gapped at around .040

Thanks everyone for the suggestions, this was my first post on here but i've been using this forum's sticky posts for quite a while
 
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