Yeah that's my plan today. Also want to check my eng bar fuses since they're related to the O2 sensors. Afr is actually reading on my AP, but my ltft switches between -.16 and 20.12 based on whether I'm on the gas or not. Car isn't dying when hitting bumps now with the new MAF.
PRV replaced, fuel pressure still tests low while off
- Thread starter Sand
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Lowboy_E
Greenie N00B Member
By the grace of the speed gods above I need some kind of reply to this thread… my short term and long term fuel trims have been the exact same -.16 at idle and once you get on the gas they drop to like -20/-15… have a cyl 4 misfire that decided to stick around on that cylinder, I’ve had a misfire on every cylinder except 3. As of rn there’s a misfire under load on cyl 4 and I’ve been overboosting yet I changed nothing from what the previous owner had.
Idk how this thread went from prv to stick fuel trims but yes I have stuck fuel trims for the last almost week after changing basically nothing… just new spark plugs that got fouled out
I work in a shop and even the master tech is kinda stumped my fuel pressures are over 1800 when they are commanded to be… smoke tested this thing 20 times to check for vac leaks I allegedly have 180 psi compression in all 4… no one at my shop has a leak down tester. I’m convinced these fuel trims may have some involvement with the misfire/ overboosting. Can’t find any other useful threads involving stuck fuel trims and I’ve been scouring the forums….
Idk how this thread went from prv to stick fuel trims but yes I have stuck fuel trims for the last almost week after changing basically nothing… just new spark plugs that got fouled out
I work in a shop and even the master tech is kinda stumped my fuel pressures are over 1800 when they are commanded to be… smoke tested this thing 20 times to check for vac leaks I allegedly have 180 psi compression in all 4… no one at my shop has a leak down tester. I’m convinced these fuel trims may have some involvement with the misfire/ overboosting. Can’t find any other useful threads involving stuck fuel trims and I’ve been scouring the forums….
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Well when I said last month that I'd be "replacing the check valve as part of a bigger job this weekend" Yeeeeah that didn't happen... I had to pull the engine for unrelated issues. I don't plan on getting the injectors cleaned but will replace that valve when I go back together and report back.
I'm not sure how that affects your problem tho
I'm not sure how that affects your problem tho
Update:
After getting the car back together and broken in, I finally got around to testing the hot engine, engine off fuel pressure thing and it was doing pretty much the same thing where the fuel pressure would slowly climb to about 1500psi, hang there, then slowly drop.
I retested the next day, this time pulling over on the side of the road after driving at like 45 mph for a little while (less idling around trying to get into my garage and heating up the fuel in the rail with the car running) and fuel pressure got to ~1800 psi and stayed there for a bit before dropping as it should
After getting the car back together and broken in, I finally got around to testing the hot engine, engine off fuel pressure thing and it was doing pretty much the same thing where the fuel pressure would slowly climb to about 1500psi, hang there, then slowly drop.
I retested the next day, this time pulling over on the side of the road after driving at like 45 mph for a little while (less idling around trying to get into my garage and heating up the fuel in the rail with the car running) and fuel pressure got to ~1800 psi and stayed there for a bit before dropping as it should
That's the part that tends to get missed. The test really needs to be done with the motor HOT
Francisco
Greenie N00B Member
Hey Cody, by any chance, when you said your car was fucked, was it sputtering when trying to drive? I'm having some issues right now with my car to where it pops up some codes for too rich at/off idle, and even crankshaft position sensor, which I've changed properly on the 20th tooth at TDC, but with my stft being -25, Will Dawson said Boost leaks can cause that code. My car is commanding too much fuel (in the 1000s) at idle, AFR at 10, but drops to 8-9 when I try pressing the gas, AFRs are at -25. Tried doing my own boost leak test with my homemade boost leak tester (hard to find one that fits the CS 4" intake, unless you guys know of one), and it only reads up to 15 psi being sent through the system, whereas it should go up to 30psi on the AP - I don't have a regulator, and Will Dawson said I'm able to monitor it through the AP and 30 is the target. I've checked and changed the fuel pressure regulator, spill valve(which helped drop my commanding pressure but still sputters), checked spark plugs, changed oil (fuel diluted) , checked for boost leaks as much as I could, and now I'm going to try doing the prv. I was just wondering if changing the prv and MAF fixed your issue?
If anyone else reads this and has more insight, please let me know. Thank you