dennybalance

Hi guys i've been dealing with a weird ongoing issue with my 1990 240sx single cam, with it not being able to idle or run without stuttering bad and cutting out. I searched everywhere and everything before posting. I have the background and what's going on right now.

As of right now:
The engine is stock besides a megan racing exhaust + cat delete and an isr fuel pressure regulator.

I bought the car like this as a daily in pretty much full working condition and drove it a few months over 5,000 miles (I bought at 145,000 and now its at 150) and all of sudden this popped up

First of all, the FPR PSI is not effected when I connect or disconnect the vacuum line, and the needle on the gauge vibrates extremely fast so the psi is always fluctuating +/- 2 psi or so, many times a second

When the FPR is set to 43 PSI the car starts right up but won't stay alive without gas or the key being held to on,

Also, the previous owner had disconnected the starter from the ignition and had it run to a button instead, and the car runs much better when the key is twisted all the way (twisted to on as if to start the car again), when let go, the car dies

The only way the car runs is when I set the FPR to maxium

Even then, the car doesn't wanna idle for a few minutes and irregularly cuts out and wants to die again while driving, but is still semi drive able (with FPR all the way open)

THE BACK STORY:
This all started when I was driving on the freeway and like a complete idiot, I didn't have the battery tied down, nor terminals fully secured and they disconnected while driving and the car shut off. When I hooked it back up it wouldn't start until I blocked off the return line off the fuel rail and got it home, and it hasn't ran the same since

What i've replaced / done:
Fuel pump
Fuel pump cover gasket
Externally wired a relay for the fuel pump
Z32 fuel filter
All four injectors
Injector o rings
Spark Plugs
Spark Plug Wires
Ignition Coil
Distributor and rotor
Another ISR FPR
Made sure timing was perfect at 15 degrees btdc

And still the car will barely run unless I max out the FPR and even then it runs like sh*t, and it all started from the battery disconnecting.

Also, what I don't get is, why does the car run much better with the key fully twisted? It's almost like normal again (I can also prevent the car from dying if I twist the key as if I was trying to start it)

Any help guys?

Thanks for reading

Silv1401

Sounds like a metering issue. Clean your MAF, and make sure the plug is all the way plugged in. Also, I wouldn't recommend the constant turning of the key to the 'start' position. That is just running your starter motor, and by running that excessively, it will severely shorten the lifespan. The reason though that keeping the key turned keeps it going is because it is forcing the flywheel to spin, which is forcing the 4-cycles of the engine, irregardless of the metered inputs (i.e fuel, air, spark). I would also put your FPR back to how it was.


Also, on a side note, have you tested or replaced the battery? Made sure the power/ground wires aren't fried? If you keep pumping the throttle/bouncing the revs will it keep the engine alive?

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S14rebuild

Get a fpr that acually works properly...then go from there

dennybalance

The starter is connected to the button so when I turn the key it doesn’t turn the starter. The idle jumps up a few hundred rpm and it revs smoother with the key turned all the way

And thanks, gonna really get in the maf this time and do that

I haven’t tried the battery yet but that’s the next thing I’m gonna do, that and the connectors

And yeah the throttle will keep it alive mostly

dennybalance

Yeah

I tried two isr ones, two stock ones and two eBay ones with all the same results, any other ones I should try?

Silv1401

I don't think your problem is fuel delivery. It sounds more like air metering or electrical. I had a buddy who was having power, charging, rough idle, and ignition issues. I told him to check his battery like 20 times after he had done a bunch of other dumb shit. Finally listened to me, turned out he had a couple dead cells in the battery. Replaced it, and all was good.

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dennybalance

Gotchu man, thanks