:::2/27/13:::

im just now finally getting my car started, and im having an issue with engine power.

at around 2000 rpms the car starts to feel like its dropping a cylinder or two, and runs a little rough, then cleans up around 2500 and at 3000 it revs perfectly smooth. it happens when free revving, and when driving.

Idle is great.


::::: DIAGNOSIS :::::

So far....

- Ive ohmed out each coil pack at 9 ohms (per factory spec .6 - 1.0 ohms)

- the injectors are brand new, i have not ohmed them out yet. but its one of the things on my list

- i just adjusted the TPS to 0.44v at idle, and it hits 4.51v at WOT and i didnt see any voltage drops of fluctuations no matter how slowly i opened the throttle.

- Timing i am not exactly sure on, i removed the CAS from the car, and put it in exactly how i took it out (matched up the dark marks) so i might still need to re-time it a bit. (but even 1 or 2 degrees of timing shouldnt effect just a specific RPM range?)

-Knock sensors are new, and not throwing codes.

-the only code i am getting out of the ECU is code 54 (transmission ecu missing obviously)

-fuel pump is getting perfect voltage, and is brand new

-MAF was cleaned with a MAF sensor cleaner aerosol.

-pcv is vented directly into a catch can, and then goes back into the intake pipe (there is no check valve, so the intake is constantly pulling on the PCV, will that make a negative difference?)

-I am not running any EGR, but i havent heard of anyone having a problem from that (and i havent on my KA which hasnt had an egr for years)

has anyone encountered this problem, or have any suggestions?

ive done a lot of searching and im trying out every suggestion i can find.

:: 2/28/13 ::

interesting development.. i dont know if it matters, but i ohmed out each of my injectors, and they all were at 36 ohms.. they are 370cc's. but they ohm a bit higher than stock, much different than the stock 10-14 ohms... MAF is showing good voltage.. .2v Key on, engine off.. 1.4v at idle, and steadily climbs through the rpm range. went out and checked the resistance of the actual injector coil, and it was 11.2 ohms.. at the harness 8 pin connector im getting 40 ohms... i checked the harness from the 8 pin connector to the injector clip and found 12 ohms worth of resistance built up in the wiring alone.. ill keep looking into other problems, but ill definitely choke this up to being potential for some failure.

:::3/1/13::::

i got a Fuel pressure gauge, and key on engine off its got 55 psi, and when running its sitting steady at 45psi, i disconnected the FPR, and it jumped up to 55 psi, so i believe everything in the fuel system is working properly.

I got a timing light, and found that i must be around 25 degrees btdc.. instead of 15.

using this method....

http://q45.org/checktiming.html

its at the last timing mark (going clockwise) so i need to adjust the timing a bit..



::::3/1/13... LATER THAT DAY::::
Ok, so i adjusted the timing to a perfect 15 btdc, and the car is idling a bit different, and i thought it might be on its way to being awesome.

i pulled out of the driveway and got to a straight street and the car actually accellerated very nicely, i shifted, turned around and drove back, and when i pulled into the driveway, i got to enjoy a lovely mis-fire. Fuel pressure still sitting at 45 psi, timing still nice at stuck at 15 btdc.

coil packs all ohm out good, injectors all ohm out good. timing is spot on.. it ran powerful for once, but after the awesome run, it started misfiring and running like ****.

still trying to figure out what could be going on..

oh yeah, knock sensors both ohm out to about 566k ohms

also still no CEL.

after several hours of pondering yesterday i think this issue happens only when the car goes into closed loop.. because right when i fire the car up, it idles perfect, and revs smooth, etc etc. once it goes into closed loop is when it starts to hesitate and mis-fire.

im thinking it could be an exhaust leak right before the o2 sensor. even though the car isnt throwing codes, im running 2 v bands on the headers, which i know are prone to leaking.. if a little bit of extra air is in there, the car might think its running lean, and start dumping fuel.. thats where i am sitting at now in my diagnostics / estimates.

please feel free to add any input.

injector ohms are way off, my car has dropped 6 of the 8 injectors in the past 2 years of running! just a thought, my car will sometimes run crappy after i flog on it hard and then i rev it up and it goes away, i think that another injector is going out! i would definitely look into the injectors just from my personal experience! best of luck! n/m just read the ohms reading you took at the injector!

most definitely not the injectors, as 1 - they are brand new, 2 - the injectors themselves ohm out at 11.2 ohms each (perfect within spec) still hunting down this bucking / hesitation issue

what fuel pump are you running?

newbissan-tech wrote:what fuel pump are you running?

circuit sports 300lph.

it holds a steady 45psi fuel pressure at all times.

and just as an update to reflect my other help threads i have posted around the internet...

I'm not tossing out black smoke. it just runs rich enough to mis-fire once warmed up. and there is the occasional popping in the exhaust

ill mess around with the MAF tonight and see if anything changes.. i checked the voltages, and they are pretty much spot on with what the factory recommends.. .2v key on engine off, and 1.3v idle running, and voltage steady climbs as you rev the engine

and for anyone who questions it, i have a 300LPH fuel pump, and a constant 45psi fuel pressure, all the time. period. never fluctuates, no matter how hard i mash the pedal.

interestingly, once the car warmed up and started running rough, i unplugged the o2 sensors, and there was zero change in the way the car ran. it still idled rough, and would misfire when lightly revving and start popping when blipping the throttle.

i havent found any thread of anyone having a similar issue, everyone claims its the MAF, but i checked the voltage at each rpm range, and the MAF is dead spot on. plus i can rev to 7000 with no problems.

i hooked up my consult and pulled up the ecu using Nistune's consult software. and what a f'ing nightmare...


all the gauges were moving and fluctuating except my TPS. The throttle position gauge wouldnt move. nistune showed the "throttle closed" red light when the throttle was closed, so i know that that part of the sensor works.

i checked my wiring and voltages at the tps (with the car key on engine off)

at the plug end of the harness coming off the ecu, on terminals A|B|C

A has no power, C has no power, and B has a solid 5v (A should be ground, B should be the signal voltage back to ECU, and C should be 5v)

once i plug in the TPS, when i back probe, i get like 0.17 v at pins C and B. i did swap my ecu after testing the TPS, so im going to swap my old ecu back in, and see if maybe the backup ECU is defective, and has a short to the TPS circuit or something..

thankfully i have my consult backing everything up..

one problem at a time

just as a follow up for anyone who might run into the same issue, or similar issue.

i had two things going against me.

1 - the ecu wasn't plugged in all the way, after back probing every wire for continuity, i wondered if it was tight enough. i managed to plug in the ecu plug another 1/4". 90% of the mis-firing went away

2 - the O2 sensors. one bank was fluctuating, the other was a steady 0.19v. i swapped the sensors from left to right, and the bad sensor changed banks. i bought 2 brand new NTK (ngk) o2 sensors, and plugged them in, all my drive-ability problems went away.

thanks for chronicling your problem and solution so well. Added this to my vh45 favs