Lean acceleration

[xracerx972]

So my cars been doing fine over the past few thousand miles, but one day just decides it wants to lean out (17:1)ridiculously under light to moderate acceleration. To me, it seems like a fuel delivery issue, but it goes away (normal afr)after the rpm equalizes with the throttle position. and it seems fine under boost.. It seems only affected during normal no boost driving.

The fuel pump seems fine, its wired through a relay to the battery. I run a map setup, so vacuum leaks are a highly unlikely culprit. Ive changed the fuel filter. The pump and injectors are less than a year old (not clogged or defective)

Im wondering if this sounds like a fuel pressure regulator issue, as in its not maintaining the pressure needed for sudden TPS fluctuations.

What do you guys think?

[Yellow4g63]

could be a exhaust leak before the 02 sensor. Or your fuel filter needs to be changed, or a voltage problem like battery or alternator going bad.

[xracerx972]

its not a faulty reading, you can actually feel the car bog for a second and Ive already changed the filter. Ive got a PFC and it shows 14v while running so I know my alternator is working.. hmm..

[Yellow4g63]

Did you turn off the 02 input on the PFC? and what kind of wideband do you have?

[xracerx972]

yes and innovate lc1.. i never leave o2 feedback on

[Yellow4g63]

Stock injectors? it sounds like it might be the injector lag time or latency isn't setup right.

[xracerx972]

Thats interesting, I can double check, but I havent changed those settings and it wasnt doing this before.
Old SIZE / New Size = Correction
New Latency - Old Latency = Latency Correction

Ive verified voltage at the pump @13.xV and tried a walbro 255 and cs340..

The only thing I can think of is maybe a hole in the line inside the tank or a faulty FPR.. what are symptoms of a dying FPR?

[Nesquick]

I had an Innovate LC-1 that went bad on me after about 600kms.
The car ran fine and nothing in the tune changed at all. It would just show 9.0 at idle and then --.- when driving.

I swapped to AEM and it was fin after that.

GL

[xracerx972]

http://youtu.be/Vuy8xmN63nM

I made a video to show what its doing, Im really leaning towards a sticky FPR at this point..

[mattblancarte]

Injector duty looks suspiciously low to me... I assume you have a good explanation for it going to 0% when you pop the throttle?

Why not just test the fuel pressure? Seems like the logical next step here.

[xracerx972]

IDC is low because the car is idling and I have 850cc injectors.

When it shows 0% momentarily, the engine is decelerating and the throttle is closed. This is normal.

I made the thread in hopes that someone with experience with a failing FPR would chime in and confirm or refute my findings, not because I'm so lost as to what's happening with my own car.

[mattblancarte]

Ah, 850cc injectors would have been good to know about... I wouldn't have asked if you had addressed injector size when it was asked earlier in the thread.

I didn't watch the video closely enough. I thought it was going to 0% as you hit the throttle, and only seeing it at 1-2% was surprising. I should have phrased it as, "why is your duty barely going up at all?"

You didn't find anything substantive to confirm or refute. Like I already asked, why not just test the fuel pressure? If the regulator is stuck and choking fuel, you can just watch it from the engine bay. No need to guess here. Do the basic diagnostic work.

No one said you are lost. Don't be rude, man.

[xracerx972]

Youre right, sorry.. Didnt mean to be rude..

I did verify the operation of the FPR by feeling the supply line pressurize after I pulled the vacuum line. Ive tried two different fuel pumps, both less than a year old..

I just think the FPR is not actuating as fast as it should..

and thank you for the input BTW, theres not much info out there about failing FPRs..

[mattblancarte]

No worries at all, man.

It just doesn't sound like a regulator issue to me, although it could be stuck... When FRP fail they tend to get a leaky diaphragm, which will over-pressurize your system and potentially cause it to run rich. You probably would have also noticed fuel in the vacuum line if that sort of failure had occurred.

That said, it's also possible to have the diaphragm stick (as you've been suggesting).

This video has a super clear explanation on how to diagnose potential failures around the FPR: https://www.youtube.com/watch?v=peh7-pFycyc

Either way, you are gonna want to get a pressure gauge/kit and do a real test. You might even just take off the FPR and inspect it.

[xracerx972]

Right, Im looking at an Aeromotive kit that will have a gauge, so that will easily diagnose fuel supply issues..

Hopefully someone else some day can also learn from this if they ever have the same issue..

[xracerx972]

Well, here's a dollar for mattblancarte - it was not the FPR. I installed rawbrokerage's aeromotive fpr kit and it did not solve the problem.

So far:
Fuel pump is receiving correct voltage
fuel rail is staying pressurized (FPR has a gauge)
CAS is set to 15° @ idle
Fuel filter is new
splitfire coils look to be in good shape (no cracks etc)
O2 sensor is new


Im starting to lean towards an ignition issue now.. this is killing me.. Its not enough of a problem to leave the car parked and not drive it.. just enough to piss you off every time you do..

[Yellow4g63]

did you hard wire fuel pump to battery and setup a relay to switch it on with the stock harness?

[xracerx972]

Yes and Ive been testing the wiring and replaced that wiring like 3 times now thinking thats what it was..

[xracerx972]

So today I verified mechanical timing and also did a compression test (no bueno) all 6 were around the 120 mark -_- To say this engine is tired may be an understatement.

Anyway, it would appear that one of the spark plugs is not firing so well - top left - which again points me towards faulty ignition.. Im getting tired of chasing demons..

I know some are saying "stop and rebuild/replace", but even then, I don't want to be dealing with this same issue..