shroom

Hey guys.

I'm running a supercharged setup on a DE-K in my 96 SE. I bought the car from Matty who did all of the work as the previous owner. Car was running super great when I bought it, despite not having a proper tune, except for this weird issue which would arise sometimes where the engine would just geek out, lose torque and power, and the tone would change from sweet & perfect to lower and raspy and the exhaust would sound almost rattle-y. It will still drive in this state, but if I try to give it throttle to accelerate quickly it will run lean-ish, spiking up to 16 momentarily before catching up with itself, but it will keep spiking lean if I stay on the throttle. If I drive it conservatively it is safe to drive, albeit at a great loss of power, almost like it's running on fewer cylinders or in limp mode. Although if it were limp mode I don't think it would be able to stay at the same RPM levels, but it's still able to rev high enough for normal highway driving (3-5k is still fine).

I thought maybe it was the fuel pump causing this, so me and Matt replaced it this weekend. The car has definitely benefited from the new fuel pump and is a lot stronger, and the issue almost seemed to be gone as the car has been running great all weekend, but the issue still came up again this morning after about 20 miles of driving.

I am almost at a complete loss here as to what might be causing this. I may end up just replacing each thing until I run out of things to replace. MAF is next.

Anyone have any clue or experience anything like this?

Some info on what the car is running:
Vortec T trim V2 supercharger
00vi
Z32 MAF, Pathfinder TB
555cc injectors
Walbro 255 fuel pump
Greddy EManage Ultimate

I should also mention the car was tuned around September of last year. The issue has happened both before and after the tune so I do not think it is the map.

JvG

Gas filter could cause that issue. Generally when ever a lot of fuel runs through it.

Replace only what is really needed.

No need to waste money when you don't need to.

shroom

I've purchased a fuel filter even though I don't think that's the cause of the issue given the ON/OFF nature of how the issue occurs - normally it'll drive fine but either randomly or sometimes when I pull hard it will go into "**** mode" and start running like ***, with the loss of power and the weird change in the engine's tone.

I'm not getting any codes related to running lean or anything that would provide insight into this issue. No codes have come up specifically from this happening. Right now my CEL is a little cluttered with some other unresolved issues from damaged wiring (that's another story) but this issue preceded this damage and is unrelated from what I can tell, but nothing has come up exclusively when this issue happens.

Is this actually limp mode? It seems to clear itself when I leave the car off for a while, but I can rev the car as high as I normally can (well, sortof, I dont try because it seems to run leaner when it's like this) but apart from the change in sound and the loss of power and torque it seems to drive fine. So is this really even limp mode that it's going into? If it IS limp mode then I guess it could really be anything triggering it. I thought what was happening was just something going haywire every time and causing the behavior I described.

EDIT: Could this behavior be the car for some reason running on fewer cylinders? I mean, that's what it feels like, in my non-expert analysis

The Wizard

iTrader: (43)

I'd look at the FPR next.

shroom

Thanks Wiz, I'll check that next. My intuition has been telling me fuel delivery, but I really don't know.

It's worth noting I'm pretty new to this and don't know as much as I could. I have a pretty decent scan tool that hooks up to my tune PC ( ). The software is pretty feature rich but I don't know too well how to make use of all the information available to me. I know I should hook it up and do some data logging, but what should I be looking for?

Some more information about the issue that I can add:
The car is hard to start sometimes. I have to crank it a bit, and usually give it a little bit of gas to get it started, otherwise it just keeps trying to start and doesn't really go anywhere. Other times, it starts completely fine right away without touching the gas. Seems to be related to the colder weather. When it's warm, I have virtually no issues.
Car used to die in neutral sometimes. It hasn't happened lately anymore but I do notice the rare dip in RPM at idle. Perhaps misfires.
I do have a fuel pressure gauge on my pillar cluster. It hasn't been working lately, but when it did the fuel pressure always looked fine. Really need to get it reconnected.

jholley

iTrader: (13)

Almost certain you have a transducer in your fuel rail that coverts to an electrical fuel pressure gauge on your pillar. Troubleshoot that transducer and it's wires that no longer gives a reading to the electrical fuel pressure gauge. While doing that temporarily replace the transducer with a T fitted analog fuel pressure gauge for a more accurate reading.