Tyblat

Hey guys. The RX7 that we've been working on for awhile is nearly complete. The engine was built, assembled, and installed. Under WOT the car behaves perfectly fine, pulls hard. The issue is idle and driving normally. It bucks and then will die. The car does have a heavy racing clutch in it, I'm thinking that is the cause of the bucking at low speeds (or at least a possibility.) The car was originally an S5 GTU N/A, It now has a Jspec Turbo rebuilt motor in it, RETAINING the N/A harness, it has the N370 pressure sensor, and N370 ECU.

The TPS is brand new, and has been re calibrated. They for some reason did not hook up the BAC valve, so they just capped it off (which would explain why the car idles like absolute garbage from cold until it warms up, you have to keep your foot on the gas to keep it alive...I do not know WHY they simply did not hook it up, its literally one hose. but I digress.)


Even when warm, the car will just die. sometimes it will hold idle or surge a tiny bit hunting (a tiny bit.) but a significant amount of the time it just dies. Either you are WOT and pulling hard, or its bucking and wanting to die in neutral or at a stop in neutral..

I'm going down there to look at the car tomorrow and figure this out.

Could it be the shop connected the primaries/secondaries wrong? I figured given the length of the wire harness that would be difficult considering they aren't all equal length for each injector.
I thought this could be a possibility because at 3600RPM they are all firing regardless, which would explain why the issue isnt there when you are flooring it WOT to redline.

I'm doubting its the ECU, seeing as how the car starts eventually, and well, a WOT pull, that kind of makes me think its not ECU related. the ECU I installed is an N370, USDM Turbo II ECU.

.. The shop seemed to think it was related to the knock sensor sending the wrong signal to the ECU, as he said the power steering wire on the N/A harness is what would be for the knock sensor on the turbo engine. (I think he is referring to S4 Turbo II swaps, but this is obviously an S5)

If memory serves... you only have to change two wires on the N/A harness. One for the knock sensor that is ORIGINALLY for the VDI which you cut wire off the plug on N/A harness, splice into knock sensor. wire)

From what i've found and to my knowledge, this is all you need to change for an S5 NA harness to work on an S5 jspec swap:

1) Plug 6PI connector into turbo duty solenoid (ECU pin 3R)
2) Cut VDI plug off and connect ECU-side wire (Y/B) to knock sensor (ECU pin 2M)


I believe the line off the compressor outlet is going straight to wastegate. The car does not have a cat, just straight piped to two fart cans the previous owner put on it. I don't believe its hitting fuel cut because if it pulls hard under WOT, well, that pretty much rules that out for the most part.

Plenty of gas in the car. It just will not hold idle at all and bucks when gently driving it. Anyone have any suggestions? I'm going to check the injectors tomorrow. I wouldnt think it would be possible to confuse a primary connector with a secondary due to harness length like I said, but I'm going to check anyway.

Anyone have any ideas they could toss in, maybe somethng I'm missing? also, isnt the idle on the TII regulated by the BAC?

insightful

the BAC harness on the n/a usually won't reach on the turbo motors without extending the wires, and that's quite simply too much work to ask of some shops that do lazy work. which airflow meter is being used? who did the work?

if you continue having problems you can send me a pm, im not too far from you and could check out the car.

from your description of bucking it sounds like its running lean, ie a vacuum leak, low fuel pressure, or faulty airflow meter.

j9fd3s

iTrader: (3)

it will want the BAC to idle right, i'd also check it for codes too. there are a few that either don't light the light, and/or get stored but have a limp home/safety function, they tend to get set with the key on, but before the engine is all the way together too

Tyblat

Double post

Tyblat

Turned out to be an rx8 injector in the primary slot. Replaced with two 550ccs of proper impedance. Car runs fine..however on cold start or warm, if you cut it off and let it sit...it does not want to start back up easily. It will die right away or sometimes work itself up to normal idle. Leaky injectors maybe? Drives fine otherwise.

Also, car is running the NA MAF. 5lbs of boost stable.