OK, just got back from R&D Dyno-problems-PLEASE HELP!

[jdm_s14_zenki]

I have a s14 blacktop motor, toda 264 cams, ferrea stainless valves, port and polish head, toda valvesprings. stock everything else except for exhaust and S-AFC2.

Ok heres the story.

My MBC crapped out on me. It took me a while to find out what the problem was. I redid the timing, cleaned out throttle body, replaced vacuum hoses, got new hose clamps and couplings, cleaned sensors,ect ect.

Finally i replaced the MBC and that fixed the problem I was having. BUT, now my car feels less powerful. Last time I went to go get my AFC tuned, we managed to get the car to 255HP/255TQ @ 14psi boost.

I just went to get it retuned again today and pulled 230HP/230TQ @ 15psi (stock turbo)

So, we also noticed that when accelerating, the motor felt like it was slightly stumbling and this is probably the cause of lower horsepower.

I just got new sparkplugs a few days ago (NGK iridiums 7 gapped at 32)

When i went into the dyno, i was running VERY lean so im thinking maybe i fouled the new plugs already.

We tried to diagnose the problem by unplugging each coilpack and sure enough when we unplugged cylinder 3 & 4 my motor didnt stumble that much at all like the first 2 cylinders did.

I just need to know some of your opinions on what steps i should take in fixing the problem. Ive been though enough with this car and im tired and im broke. Let me kn ow what you guys think. Thanks!

[nrg]

first do a compression check.
pick up reg copper plugs for 1.98 ngk-r pre gapped to .028 and try those out
maybe bad coilpack and harness. check for ecu codes, boost leak, vaccum leak.

[jdm_s14_zenki]

i havent done a compression check yet but this is what i have done so far as of right now:

I replaced the 2 bad cylinder's spark plugs and regapped to .028 using same stage 7 iridiums NGK

I unplugged coilpacks again and nothing has changed so far.

So, i switched the coilpacks around. Problem did not move to the other cylinders. The problem stayed on #3 & #4. Therefor the coilpacks and spark plugs arent the problem at all.

However i was looking at the injector harness. its very close to the stock exhaust manifold and i dont have a heat shield on the manifold. I have a crappy looking heat cover on the harness itself though but it looks burnt up.

It may be possible that the heat might have slightly messed up the wires to the injectors??

Also another problem arised. I cannot bring up my idle past 850 with lights off and 770 with lights on. as soon as i turn on the headlights, my idle drops to 750-770...i unplugged tps and tried to set idle over again and it will not go up. only down. this is scaring me. hopefully its a bad wire or bad ground on the injector harness.

How do i check if the wiring/ground is bad on the injector harness?

BTW: My car drives OK when im driving...idle is horible though. but the idle doesnt fluctuate to much as if it were a vacuum leak or boost leak. i get full boost of 1bar.

[nrg]

How did you regap iridium plugs? didn't think you can.

check for check engine codes. sounds like a bad sensor.

[jdm_s14_zenki]

they come pregapped at .044
i was told at superautobacs that you can regap. shouldnt be a problem.

maybe i should try using the stock plugs again..maybe my car doesnt like those iridiums..

man im stumped..under throttle the car drives pretty good..im just not making the horsepower i used to..i was also told at the dyno that my boost would hit 1bar at around 3600 rpm then start dropping down to .9 afterwards but thats not that much of a difference..

it idles pretty consistently but sounds like crap..

how do i check for engine codes?

[SoSideways]

You gotta use the hook style regapper tool, instead of the "disk" styled ones. Disk styled ones break off electrode tips, ask me how I know :(

[Maeda]

Do a compression test. 1 bar on stock turbo leads to disaster time and again.

Oh and MBC = fail.

[jdm_s14_zenki]

1bar on a t28 with a built head should be ok for the motor?? at least thats what all the threads on fresh alloy and zilvia say...even heavy throttle says 15psi is max safe boost. i have an s14blacktop with stock t28 turbo, stock injectors, stock mafs.. maybe my mafs is taking a crap on me? when i unplug it my idle levels out and sounds a little better but the car eventually dies out..

i just picked up a compression tester, ill test it tonite and post the results...


when seeting idle speed, i unplug my tpc and my idle is anywhere fom 980-1100rpm, then when i plug it in, it drops to about 820-860

also when i turn on my headlights, my idle drops like 50-60rpm and stays, is this normal?

[jdm_s14_zenki]

You gotta use the hook style regapper tool, instead of the "disk" styled ones. Disk styled ones break off electrode tips, ask me how I know :(
u know what, ur right...i replaced 2 spark plugs with new plugs last nite..the tips on the old ones werent there...and the tips on the new ones look real fragile...where do i get the hook style gapper???

[jdm_s14_zenki]

update:
today at a shop, i tested the coilpacks again by unplugging them. all 4 stumble equally now..i did this on a warm engine..

It feels like im running REAL rich..my settings on the AFC are as follows.

throttle=30% low 50% high
LOW:
1000rpm=25
2000rpm=27
3000rpm=24
4000rpm=2
5000rpm=1
6000rpm= -1
8000rpm= -5

High:
1000rpm= 12
2000rpm= 18
3000rpm= 17
4000rpm= 8
5000rpm= -4
6000rpm= -11
8000rpm= -19

[jdm_s14_zenki]

ok grabbed some stock spark plugs at the dealership today...im going to do a compression test tonite, i will also reset the cam timing and start from scratch again..

any suggestions before i waste my time?

[smithers584]

well you stated that you were running very lean, i would check the fuel pressure regulator. you are also running +25% at idle on your SAFC II? Why? are you on the stock fuel pump? even then i wouldnt have +25 at idle on the low throttle setting. but then you confuse me cuz now you think you are running rich, any idea which it actually is? i imagine you are running really rich at idle and probably pretty lean at high throttle, just by looking at your settings. i would back down the fuel at all your low throttle settings, and probably at 1000 drop it down to about zero. usually you can back it down until you idel smooth and keep going down till its rough again, then add a little to smoothen it back out. if you are on the stock fuel pump your high throttle settings look extremely lean, but this is all going on the very little i know about SAFCII.

[jdm_s14_zenki]

i have a walbro fp as well. before i got it tuned yesterday i was running lean...1000rpm was at +3 (from what they told me) these are the settings they they put into my afc. i tried turning the fuel down @ 1000 but it started running real crappy..so i had to turn it up again to 25 and that smoothed it out better but still crappy..

[jdm_s14_zenki]

how do i check the FPR? or do u mean check the fuel pressure itself?

[smithers584]

yeah dude you might have some other issue causing it, i think you need to look at the FPR and the Fuel pressure to it. if you have the stock FPR, take of the vacumm line and plug it with your finger, youll need a gauge inline to tell if the pressure rises or not. if its good fuel pressure will increase as vacumm decreases, i believe with the vacum line on it should be set at 36 psi and with it off it should go up to 43. if all that looks good, i would probably get a new one or someone else to test anyways.

[jdm_s14_zenki]

man, this sux. it is a stock FPR...i was thinking more along the lines of timing cus i do have adjustable cam sprockets and when i had the valve cover open (a while ago) i advanced the timing like 5 degrees to make up for the loss of the bottom/midrange power that comes along with the cams i have. i dont know...i guess i'll take it to a shop and get my ass raped some more.

now that i think about it, i do have my boost guage hose hooked up the the FPR vacuum line..maybe theres a leak...but my boost guage reads vacuum and boost just fine...

[Maeda]

Try the fpr it could be stumbling because of that too...

If you can, try and swap ALL 4 coil packs. Dirty D had some stumbling problems and it was because they were a bit weak. They all worked but under heavy load they just couldnt put out enough spark.

[smithers584]

dont take it somewhere and get raped, just borrow some tools and download the FSM. if you are somewhat mechanically inclined you will learn tons from the FSM. you can do a lot of testing to narrow it down and learn a lot in the process. and, we are here to help you also. just take the time to atleast check all your sensors and wiring, maybe 30 minutes to do everything. first though we need to know if it is lean or rich, or any other conditions, when its happening, what engine temps, all that good stuff.

[smithers584]

also, my vacumm gauge read good on my car too, around 20psi, but when i hooked up my homemade leak tester, i found a big ass leak on my cold pipe, clamp wasnt tight enough around TB.

[Maeda]

Speaking of clamps. Are you using T-bolt clamps?

[smithers584]

yeah t bolts are a must, if you dont have them get them. here is a link on how to check your IC piping for leaks, really easy, give it a try. i made this for like 10 bucks.

http://www.zilvia.net/f/showthread.php?t=106184

[jdm_s14_zenki]

i dont have any t-bolt clamps, i do have the fsm and some tools..i need to find someone thats willing to swap out my coilpacks and MAFS. i dont have anything to read the engine temp. i do have a multimeter..

Well ill check everything out some more tonite and i'll post the results later tonite. thanks for the help guys.

btw, is there anyone in the socal area that knows this car better then i do? i need help checking these things out...i'll reward you if you help me! im in desperate need! haha..seriously though

[Maeda]

btw, is there anyone in the socal area that knows this car better then i do? i need help checking these things out...i'll reward you if you help me! im in desperate need! haha..seriously though

You live too far, and I don't have THAT much time to waste. :D

The forums will be here to help though.

Oh, and another thing. I swear R&D's dyno reads LOW.

[jdm_s14_zenki]

update!

-ok, checked timing...
the last time i checked my timing, i used that loop on the harness for a signal. This time i used the #1 cylinder harness for a signal. What i noticed is that #1 signal is MUCH more accurate for timing then the loop. If using the loop, the timing shows +5 to +10 advance. Thats where i messed up! So when i checked the timing today, using #1 cylinder, my timing was -5 to -8 degrees off (retarded)

-did the timing again, didnt even have to reset the cam gears, reset idle speed and we're good to go. Im running about 15 to 16 btdc and man, the car feels more powerful then ever!

Now i just need to make sure im not detonating either on low or high end..

Hey! do you know what to listen for or what pinging/detonating sounds like?
Should i be driving when i try to listen? isnt kinda hard with the exhaust and bov and turbo noise?

[fliprayzin240sx]

Umm...honestly i wouldnt recommend driving it and "listening" to it. Thats how you blow bottom ends up specially on a 370cc injectors. Find somebody with a wideband and street tune the car atleast.