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Geovannie
09-25-2005, 06:07 AM
background

S13 blacktop
GT25R
550s
Enthalpy ECU
Z32 Maf
AFC
Top Speed Intake Manifold
Walbro 255hp rewired
HKS 264s

I think that is everything major. Doing some racing yesterday running 19psi and pump gas as I usually run on the street I had a issue. I go around 2nd gear 45mph, shift to third all good but in the middle of third it started breaking up bad so I let off. Push the clutch in an free revved it sounds like a WRX. Pull over and go through everything.

Since the car sounds like it is on 2 cylinders I thought I blew it up however there is no blowby at all, car does not smoke, idles fine at the same 10" of vacuum as normal 950rpm. I start pulling coil pack clips and the tone changes as I pull each one indicating that they all work. 1 and 4 sometimes for some reason did not change the tone and after a few seconds it did. Then I did the same thing with injector clips. The car will run with 2 and 4 disconnected, but if I connect those 2 and unplug 1 it will try to die and if I disconnect 3 it will die. I can unplug 2 and 4 and start the car and have it run. It does change the tone of the exhaust indicating that they are working though.

I'm not sure what could be the problem. I just did a compression test and got 175,180,178,175. Everything seems fine but it definately does not run good at all. Anybody got any ideas?

ncsr20det
09-25-2005, 07:37 AM
Check the maf

cwdmark
09-25-2005, 10:46 AM
your compression looks fine, make sure you do the test at wot

change your plugs. if it still breaks up its either coilpacks or maf.

bl200sx
09-25-2005, 11:20 AM
Check your injector wires, when I installed my sard 550cc I didn't have one of the plugs on good, it ran on 3 cylinders, til I put it on.

rogoman
09-25-2005, 12:20 PM
idles fine at the same 10" of vacuum as normal 950rpm.



With the motor fully warmed up, the reading at idle should be 18 - 20 InHg instead of 10. You may have a major vacuum leak.

_Def_
09-25-2005, 12:43 PM
Big cams reduce vacuum at idle. -10 in-Hg is normal from what I hear with 264's.

Geovannie
09-25-2005, 05:54 PM
Maf wiring is fine, it is reading airflow as normal on the afc as well.

Spark plugs are in perfect condition. Burning great. They are Denso Iridiums. As somebody else said that is my normal vacuum.

I will hopefully look at it more tomorrow I had other stuff to do today.

BlazedGlory
09-25-2005, 05:59 PM
your compression looks fine, make sure you do the test at wot

change your plugs. if it still breaks up its either coilpacks or maf.



or the wiring... so test the harness plug for power first...

I recently had a coil pack go bad. It gradually went. It started missing when the car was cold for a couple days, then it would run on 3 cylinders for a while and occasionally hit. Then it just went bad. I ended up unplugging that injector and that coilpack so it wouldn't dump all that fuel in the cylinder then pop when it occasionally hit until I got my coilpack in. I did notice when I pulled the bad coil pack that the 3 connector things were kind of rusted out a bit. I don't know if that's what always happens when they go bad, but it's worth a check maybe.

Also, the only place I could find new coilpacks for my blacktop was charging like $79 each I think. With a careful selection I got 4 used coil packs, the harness, and even the harness mounting bracket for $65 shipped (ebay). The first coil pack I tried worked, so I'm assuming I have 3 working spares and the harness all for less than the cost of one new one =P.

Just make sure you check wires out too before you replace parts they are going to.

Good luck!

cwdmark
09-26-2005, 04:18 AM
Spark plugs are in perfect condition. Burning great. They are Denso Iridiums.


change them anyway. put in a set of cheap denso coppers from a 91 sentra se-r and see if that helps.

trust me, just changed what looked like a PERFECT set of plugs and that fixed the major breakup issue i was having. it wouldn't even get to 8psi before popping. i change plugs every 3k or less http://forums.freshalloy.com/images/graemlins/grin.gif

BlazedGlory
09-26-2005, 04:50 AM
Spark plugs are in perfect condition. Burning great. They are Denso Iridiums.


change them anyway. put in a set of cheap denso coppers from a 91 sentra se-r and see if that helps.

trust me, just changed what looked like a PERFECT set of plugs and that fixed the major breakup issue i was having. it wouldn't even get to 8psi before popping. i change plugs every 3k or less http://forums.freshalloy.com/images/graemlins/grin.gif



should he check the plug gap even maybe?

cwdmark
09-26-2005, 12:51 PM
plugs do open up gap over time, but usually don't need regapping (or so they say).

has it rained in your area lately? if so make sure the ecu isn't getting wet either, that happened to me a couple times and caused car to break up. yea, not good. gotta unplug it, blow any moisture out and put it back together.

Geovannie
09-26-2005, 05:58 PM
Nah no rain at all. I am going to borrow some coil packs hopefully tomorrow. Something is up with #4. It definately has a lot weaker spark if any than all the rest.

Geovannie
09-27-2005, 10:23 PM
Coil packs did not do anything along with new plugs. ECU flashes once then twice so code 12. Tomorrow I will check all grounds for the coil packs and the maf/afc wiring since that is what code 12 means.

Geovannie
09-28-2005, 07:38 PM
Checked coil pack grounds. Maf wiring, did not change the maf I did not think those really go bad. Physically it is fine. Maf wiring at the afc is fine.

I'm running out of ideas. If the ignitor was bad it would not run at all right?

DeatschWerks_Dave
09-29-2005, 05:22 AM
...did not change the maf I did not think those really go bad. Physically it is fine. Maf wiring at the afc is fine.



Are you joking? MAF's go bad all the time! They don't cause misfires though, unless it is just from dumping in way too much fuel

Geovannie
09-29-2005, 07:34 AM
Usually when a maf goes bad it won't even rev over 2k or so. This one revs fine, reads airflow fine on the afc as well. I will try somebody to let me try theirs for a few minutes to see if that is the problem.

Angel
09-29-2005, 09:49 AM
Usually when a maf goes bad it won't even rev over 2k or so. This one revs fine, reads airflow fine on the afc as well. I will try somebody to let me try theirs for a few minutes to see if that is the problem.



Geo
If you need to swap a few parts around with mine to diagnose just let me know. If you haven't already, check that the injectors are all firing and check the relevant grounds for the coilpacks. Also my car started acting up shortly after doing the swap and I could not find anything to explain it... I just went through and cleaned all grounds, connections, any electrical interface with electronics cleaner and a liberal coating of dielectric grease and it miraculously disapearred.

Geovannie
09-29-2005, 09:52 AM
Thanks Angel, one of the Enjuku guys offered the same so if I need something else I will let you know.

I will have to go through all the electrical connections today and make sure all injectors are working properly.

BlazedGlory
09-29-2005, 06:47 PM
Checked coil pack grounds. Maf wiring, did not change the maf I did not think those really go bad. Physically it is fine. Maf wiring at the afc is fine.

I'm running out of ideas. If the ignitor was bad it would not run at all right?



so you checked the coil pack wiring - did you try new coil packs?

Geovannie
10-01-2005, 10:18 AM
Problem was the #4 injector on the harness side had come unlose.

Finally!!!!!!!!!!!!!!!!!!