SO,

Finally took the time to address some things on the car, I did the ignition hot wire mod, swapped in an intake manifold that I mildly gasket matched and ported. I have a cold air intake, but stock everything else. deleted all emissions, have only an IACV and AIC.

I also set up for TDC Compression and carefully set the DIST base timing making sure the dimple is aligned with the notch and that the rotor is directly under plug 1. I warmed the car, shut off and unplugged the TPS. started back up perfect idle at 700 rpm and set to 20 btdc. car has a new coolant temp sensor..

So before swap and ignition mod, I had a bad stutter around 2200 on hot days with car cold. Also had to max out the dist to get even close to 20 btdc. After swap things have improved everywhere expcept that if I am too quick on the throttle the car stutters terribly.

TPS was set to .5V at closed, and is smooth to 4V but never gets above that. MAF shows .9v at idle and shows smooth increase in voltage up past 2V which is as far as I can open the throttle without blowing up in nuetral. When I stab the throttle quickly I don't lose voltage on the MAF or TPS.

Also, under heavy electrical load lights- seatbelts-defrost I do lose 200-300 rpms. I show 13v at all times on the battery and have a direct power feed to my ignition coil now.

Oh one more thing, with the MAF unplugged I can stab throttle and rev quickly to 3 grand and then choke out. MAF plugged in stab throttle 9 out of 10 times I misfire bad.

HELP I am lost and about to start throwing parts at the car. snapping the throttle to quickly could me what? Crap coil?Fuel Pressure

Any things to check would be awesome....

No Replies?

I tested my fuel pressure, only getting 30 psi using a vaccum pump to apply as much vaccum to the regulator, tested my engines' vaccum 22inhg (pretty good), tested fuel pressure with regulator hooked up normal 28psi at idle only climbed to 30psi under open throttle. So I know this isn't within spec. I removed my fuel pressure tester and then regretted it cause I had another idea to test if my pressure was due to regulator or pump.

I started running the engine with my fuel return line pinched off forcing a rise in fuel pressure. I wish I had kept the gauge on to see what actually happened. But the car still misfired under fast throttle dumps. So I am thining I will repeat this test and see what my pressure is, but this is driving me crazy.

I can rev to 7 grand fine with slow throttle _ I feel a little rise and fall of pull/torque but nothing major. I did this in 5th gear so I could fully depress the throttle without doing double the speed limit. I don't think my TPS is bad or setup wrong, my MAF seems spot on the service manual, I don't seem to have a vaccum leak...

If i stop the gas the car jerks and pulses with a misfire da-da-da-da-da until I back of, then I can rusume acceleration with a slow throttle....???

SO:

I got the fuel pressure tester kit from Autozone again - and tested the Fuel Pump 28-30 Psi at idle, rev the engine drops (very wrong) to 26-27 Psi.

Pinched the return hose off and barely climbed to 31 PSI, completely pinched off return - no change.

Replaced the fuel pump - OH YEAH! Fixed..... No more stutter, no more misfire at gear changes when the RPMS dropped around 2200k.... Still not perfect but I am getting there. I think next I will tie the ECU ground into my new grounding rig.

Oh and I did a vaccum test a few days ago - 22 in Hg spot on.

I know this thread is old, but oh well; you might have helped solve a very long term problem with my car. Thank you. I'm gonna take a video of it for you and send it, and see if my problem is as similar as you are describing it.

Well, you don't accept PMs it looks like, so I'll post the video here: http://www.youtube.com/watch?v=Q9_yYRO- ... e=youtu.be

I will check this out tonight. And look into why I can't get PMs.

It vaguely says that you have this disabled. Something like, "User does not have PM receipt activated" I think.

Anyways, they way you described your problem was exactly what I've been looking for for over a year, probably a year and a half... I've for $1400 into a rebuilt motor from a guy, and received it still running like complete s***. Thanks to you though man, I finally have a tip on what direction to look in, and it hit the nail on the head. You've personally helped me achieve a milestone with this car. I'm sure in the right hands someone could have solved it long long ago, but the experience is what I'm looking for to work on things myself.

I really appreciate your post. It's seriously a big help.

Thanks man, I was surprised when I didn't get any replies. I found like ten threads with some but not all off my symptoms. It wasn't until I decided that even it killed me I would fix the damn thing.

I was being a little stubborn thinking it couldn't be fuel flow related since it was low RPM only but I was literally out of anything left to test. So glad Autozone had a nice kit for fuel pressure to borrow.

My car runs better than any ka 240 I've had or driven in now. The last thing is to check the actual signal at the ECU connector for coolant temp cause on the coldest days I still have a tiny hesitation when engine is cold.

I also want to get rid of the side feed fuel injectors but I need to find something that can drop in to work with OEM computer I need it to run every day.

Good luck. Don't ever sell the car, I regret letting go of my three previous s13s

PS just watched your Vid and that was a little worse than what I started with. But almost identical. Mine seemed to run a little better above 2800 than yours, the injectors in these things can vary so much car to car (i went through three this year) could be why.

Did you already get a new pump on?

Yea I'm pretty sure the thread I had way back when didn't get many replies. The autozone around here typically has s*** rental equipment, because no one checks it and it comes back damaged. Whole reason I had my motor rebuilt was the compression gauge I rented was f'ed up, and sure enough I figured my compression might just be so low that it ran like piss.

I did get my pump in, and it changed for the better. It went swell. However, I am down one cylinder, due to the injector from what I can see. I'm getting a couple tonight, so we will see what happens.

I've looked into doing some top feed shenanigans too, cause this stock rail is a complete PITA.

Replaced injector, spins to redline in second. Win.