Thread: Fueling Issue 2004 gtp

I have a 2004 grand prix gtp compg and I recently replaced the fuel pump and filter after noticing i was running lean at high rpm over 5k I also noticed that in my data log my injector duty cycle was well over 80% and went up to 105%. With the new pump and filter installed I measured fuel pressure and at key on and at idle it was around 60 but when i would rev the engine in park no load the fuel pressure would drop to about 50PSI. I recently just measured a voltage drop of 1 volt on the fuel pump power side of the circuit and replaced the ground wire with 12 gauge wire. Im waiting on some A replay and relay socket to get here so I can rewire the hot side of the fuel pump circuit. My question is would a voltage drop of 1 volt cause the drop in fuel pressure and cause my injector duty cycle to max out at high rpm? I dont know what it could be im hoping re wiring the pump will solve it. I havnt been able to find much information on the l32's and the returnless fuel system for this kind of problem.

Mods
Fenderwell intake
180 stat
Autolite 104 plugs
zzp pcm 1.0
3 inch catless downpipe

sounds like you have plenty of fuel pressure. your fuel pump will benefit from a rewire because then it wont be voltage starved as much. I would suspect that your zzp 1.0 pcm is commanding a lot of fuel, any idea what your AFR is at wot and what your LTFT's are?

Under medium acceleration when i get into power enrichment my afr will be around 11.0-12.0:1 But when im at WOT my AFR sits steady close to 13.0:1. My long term fuel trim is steady around +10 in WOT.

what pulley are you running? I would pull some timing to address that kr. I asked a guy I trust about your fuel issue and he said he had yet to see an hp tuners scan with a zzp 1.0 that didn't have issues. I don't know much about 04+ cars.

did you download your stock tune before the zzp 1.0

Im running my stock pulley and Yes I saved my stock tune.

Originally Posted by J57ltr

You aren't running out of injector for sure. The issue is that HPT displays the IPW based on old tables and the 04+ will go all the way to 34ms IPW without issue. This is a returnless system so the fuel pressure is fixed. Look into the tune file and check out your IFR table and make sure it's still stock. Also check the MAF table and see what is setup there. The timing vs time vs RPM or I can't remember what it is called is usually dropped a lot up to 15 seconds then they leave it stock. The voltage drop is likely due to the alternator cutout RPM. If your sparkplug wires are close to the signal from the fuel pressure sensor then it may be affecting the reading. I had an issue where my fuel pressure gauge would go dead when I got on the gas. I would have to shut the car off open the door to kill RAP and then restart the car to get it working again. I moved the wiring and it went away.

That's a start

Jeff

do this

I dont have a fuel pressure sensor I was measuring it with a Gauge sadly I cant watch the gauge while driving it is not long enough

Originally Posted by J57ltr

you need to compare the IFR vs KPA. I don't use HPT but why do you have 0.0 up to 8250Hz?

I was showing the amount the maf table was changed over stock. I did look at my IFR vs KPA it is the same as stock.
https://i.imgur.com/gBWG5pn.png This is what my Maf table looks like

the easiest way to get rid of your kr is to subtract timing advance from your high octane timing table. to do so, you find the cells that have the kr, then subtract from those cells.

Could I be getting KR becuase my AFR is not matching my commanded Ratio? I noticed that Theres a timing correction that adds timing depending on the commanded AFR

every stock car has kr. I don't know what that table is that you are referring to, but I would be skeptical something like that would cause kr.

Imgur: The magic of the Internet This is the Table. What other mods could I do to reduce KR?
I have
Catless 3in downpipe.
Autolite 104s
180 stat
Fenderwell intake
zzp pcm 1.0
Stock pulley

I would 0 out that whole table

there are a lot of mods you can do to get rid of kr, take a look at this thread:

Safely Modding Your 3800 Powered Car!!

Originally Posted by Scottydoggs

when does the commanded af not match the Wide band? idle? or wot. and how much off is it?

also what wb, what hpt unit, how is the wb being imported to hpt?

The wideband doesn't match when at WOT the commanded is 10.9:1 and im see anywhere from a 12.0:1-13.0:1 during a pull.
I have the PLX gen 4 Wideband sensor. And my HPT unit is the MPVI2 so I currently have no way of importing my wideband data into the logs.