Random lean condition

[Carney714]

My car would randomly go lean and sputter while driving and at idle. It wants to turn off but barely kept alive. If given gas, itll go around 16.7 on my Wideband. This has happen to be before while driving a while back, and at times when i would turn on the car and let it idle.

Today, while driving to school i lost most of my power and it would sputter. Making my car lean, and throwing my car into neutral would result in my vehicle dying or almost dying. I would just throw it into first gear and jump start the vehicle

This is at random moments when it would happen, it can be at first start up or while driving. My usual fix for this is turning off the vehicle and turning it back on. Most of the time it fixes it, if not i switch over to E85 map and back to 91 map

98 GSX with 6 bolt swap
Evo Ecu
Speed density
1000 injectors
255 with rewired kit
AEM FailSafe wideband
t28 turbo (no shaft play)
and no boost leaks.

 

[iceguru1114]

This might be a 'no-duh' response, but the intermittent nature of the problem, combined with the fact that it can be solved by turning the car off and back on means that you almost certainly have an electrical issue. The fact that your engine is running lean under more conditions than just idle (you said you lost power while cruising) means that it is probably a fueling issue as opposed to an idle air control issue.

Has your car run correctly in the past with your current combination of parts and with the current ECU calibration?

Have you made any changes recently?

Did you just recently get new gas?

Can you verify that you are getting adequate fuel pressure?

Is your wiring done properly? Do you have crimped connections anywhere that could be loose? Are your grounds good?

^^That's what I'd check to start, in that order.

 

[curt-s]

Check the contacts on the harness connectors for things like the PTU, coil, and so forth. I had one that was barely making contact, and the vibration would sometimes cause intermittent hesitation, sputtering, and severe lean issue. Replaced the connector on the harness and it was solved.

Not saying this it IT, just a good thing to check anyway.

..found this out on the side of the road once.

 

[AJ2g4g63]

Hey I just joined this site and stumbled upon this thread. I too have a similar issue if any of you could help/ OP figured out the issue.

I have a fully built 2g making 405hp on E85. During my tune 2 months ago, my afrs were right around 12:1 at wot and stoich during cruise. Just over the past week, idling is maxed out (over 18:1) on my AEM Eugo Wideband and wot is right around 15.6:1. Needless to say, I haven't touched boost since this discovery. Things I have already checked/ done:

Cleaned fuel injectors properly
Replaced plugs
Changed fuel filter
Compression test (came out good)
Checked for vacuum leaks (none)
Checked turbo (running same boost with no shaft play)

Also!! It randomly started misfiring at constant cruise over 3000 rpms. All I have to do is turn the key off and back on while in gear and it drives normal again for 5-10 seconds. I have a feeling like these issues are related. Please help. Last thing I want is to melt a piston with this lean behavior after recently spending 10k on this build

 

[BlackWaspBG]

I would like to know too. When its idling sputters goes lean and dies. Before that it was chugin and goes leanish and couldn't let arond stoich. Sometimes I observed when i come back from a drive and look at the fuel pressure gauge in the engine bay that reads zero or close to around 10-15 psi.

 

[AJ2g4g63]

I would like to know too. When its idling sputters goes lean and dies. Before that it was chugin and goes leanish and couldn't let arond stoich. Sometimes I observed when i come back from a drive and look at the fuel pressure gauge in the engine bay that reads zero or close to around 10-15 psi.

Hey man, I ended up figuring this issue out. I had the same problem. For me, it was the fuel pressure regulator. Replace that, and I can almost guarantee it will work (given your fuel injectors are clean, and your fuel pump works efficiently)

If you are unsure where that is, or how to replace it-

It is the piece connected to the end of the fuel rail by the fuel return line. It is like a $10 part, but will make all the difference. Let me know if this solved the issue.

 

[AJ2g4g63]

Hey man, I ended up figuring this issue out. I had the same problem. For me, it was the fuel pressure regulator. Replace that, and I can almost guarantee it will work (given your fuel injectors are clean, and your fuel pump works efficiently)

If you are unsure where that is, or how to replace it-

It is the piece connected to the end of the fuel rail by the fuel return line. It is like a $10 part, but will make all the difference. Let me know if this solved the issue.

The problem is this: the FPU will remain open, thus returning more fuel than it should..... Thus leaving no fuel pressure in your rail. Btw, it is the piece directly connected to the return line. Not "by" it like I stated above. *brain fart*

 

[BlackWaspBG]

I have adjistable FPR. I switched a new walbro 255( I can hear it working) the gauge is reading around 25psi and it bleeds down slowly like it should but the problem is still there. By saying FPU what it stands for?

 

[AJ2g4g63]

I meant FPR. Fuel pressure regulator. Try cleaning your fuel injectors.... But with low fuel pressure, your problem has to lie either with the pump, the lines, or the FPR. Adjustable or not, it might be faulty

 

[AJ2g4g63]

I meant FPR. Fuel pressure regulator. Try cleaning your fuel injectors.... But with low fuel pressure, your problem has to lie either with the pump, the lines, or the FPR. Adjustable or not, it might be faulty

Doubtful, but the fuel filter is worth checking

 

[BlackWaspBG]

May be some line kinked. I didn't check for that. I have the SS line to the fuel rail and i put it sort of S- shape last year and ever since have no problems but the wheather here was below zero I think something happend. I am dealing with this for 4 hours and I am tired. It could be somethig electrical I have rewired the pump last summer.Put new filter. I will have to check everything but on he weekend. Thanks for your response man!

 

[iceguru1114]

May be some line kinked. I didn't check for that. I have the SS line to the fuel rail and i put it sort of S- shape last year and ever since have no problems but the wheather here was below zero I think something happend. I am dealing with this for 4 hours and I am tired. It could be somethig electrical I have rewired the pump last summer.Put new filter. I will have to check everything but on he weekend. Thanks for your response man!

First thing I'd do is remove the fuel feed line going to the rail, route it to a safe location to pour gas, then kick the pump on to sanity check that you have good flow to the rail. Note: pressure does not necessarily correlate to flow.

If you have an adjustable FPR, and you've successfully eliminated all other potential sources for fuel flow restriction/fluctation, AND you're also certain there are no air leaks and/or ECU idle map tuning issues be sure that:

1) Your FPR diaphram is not leaking
2) Your FPR ball valve is clean and seating properly
3) You have the appropriate spring in for your target fuel pressure
4) Probably the most important and often overlooked: you have to run an air reference line from post throttle manifold to the FPR diaphram to ensure a constant deltaP across the injectors

A note about injectors: just because your injectors are clean does not mean they are seating properly or flowing correctly; injectors get worn out especially if contaminated fuel was used at some point in time.

Also, speaking logically, if you made a change and the problem began after said change was made, that's a pretty good place to begin your troubleshooting.

Best of luck, man

 

[Stephen227]

What are your maf readings like when the car starts hesitating? See if there are any fluctuations(especially at cruise)

 

[Dsmkauai]

Why is your fuel pressure only 25psi? That's not right bro. Check it with the vac line off and make sure it's 43.5 which is the factory spec.

 

[BlackWaspBG]

Thanks to all for your replys. Found that the AFPR was thr culprit. Removed it put the stock fpr( I drive 1g) and problem is solved. Dissasembled the AFPR checked spring, diaphragm, ball seat everything looks ok. Now I am running with the stock fpr and the 255 walbro till i get another AFPR but this time wont be Aeromotive. Dissapointed! Very! So again thank you all! And sorry for my english