I have searched for quite a while now, and have checked timing, tps, vaccum leaks, played with the idle screw on top, and the 8mm one on the top side that controls the upper throttle plates.

Emissions are removed except BAC and air bypass solenoid valve.

The motor is supposedly a 3mm, street ported s4 n/a and I just finished swapping it.

You will see in the video the motor wants to rock alot at idle. I have played around with the tps while it was idling and it did not seem to help either. Is this how its soppose to run ported n all? or is something.

When driving it there is hesitation, and gives a feeling of boost (ITs not boosted), i.e when you floor it while driving it will hesitate a little till around 4k then take off normal after that. All of my grounds are present and in good condition just recently went through and hit them with a wire brush.

Does this leave fuel as my problem or is this strictly something else?


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Theres a tube right on top there thats kinked... could cause problems.

 

Even with that hose not connected or my bac unplugged it didnt change my idle

 

lol, that's the coolant hose that normally runs from the thermowax to the BAC, then to the rear iron. Except he looped it back on itself. It's not doing anything at this point. Take it off, it's useless.

 

I wasnt sure if I could have a vac leak thru there.

 

What is the idle speed?

 

Well i was able to get my idle normal. I had to reset my throttle plates to their original oem location (yes they had been messed with). Anyways was able to get it to start up rev to 3k and slowly die down to idle and hold at about 900. (streetported). Set my tps to 1 once it was warm, then took it around the block and drove it pretty hard, stopped the car and the idle was HUNTING at about 2k to 1500 and the screw on the top was all the way in. I tried adjusting the tps and it would not stop the hunting. If i somehow still have a vaccum leak why would it start after spirited driving?

 

probably cause the thermowax (n/a cars have that right?). im just making a wild guess, but perhaps when the car warms up the idle lowers and thus less vacuum causing small leaks to be more problematic than they would be at a higher idle.

i've had/still having similiar issues with my t2, but im not sure if they're the same you're experiencing. for one, with my old engine (i recently swapped a lower mileage jdm motor in) it would shake a lot because of misfires. with my jdm motor when the timing was off it would not idle steady either, but after adjusting the time it ran smooth as butter (when it was cold).

i just bypassed the coolant from my uim, replaced old hoses, clamped the crap out of hoses (intake hoses, brake booster, zip tied emission hoses), and replaced gaskets. i havent tested it out yet cause i just did it today and was super tired from working on it all day. though also i neglected to check my fast idle cam and i wonder if it needed to be adjusted. oh well..we'll see tomorrow if my work paid off..

 

Oh wait, you removed the coolant hoses from the uim? Well I guess the thermowax isnt effecting it.

 

No thermowax.

 

@rumblz thats basically what i did. I swapped a lower mileage motor. And it was shaking like the video. I went thru and copied all screw settings from an unmolested throttle body and it ran smooth intil warm where it hunts and idles high.

 

Yeah, same here, great idle when cold and then idle craps out when warm. Im guessing one of the sensors changes the fuel mixture at a certain temperature ? I also have no egr, i still have the a/p and jdm acv (has no wire connector, maybe an issue) installed, but i plan on removing those too. I figured I'd just delete all emissions to make it easier to work on, but you've already done that and still have this issue..dunno maybe someone can clarify what's happening.

Also by any chance do you have a lightweight flywheel on?

 

No i have a heavy *** flywheel and what appreas to be a dying clutch... but on another note. I playeda round with the screws and what not on the tb some more and was able to get it to not hunt again , but with the lights on and blower it wouldnt hold idle. Once i shut off those the idle would return. Im guessing my alternators bad or something now.

 

The BAC is still in place, perhaps it is stuck or has completely failed. That will help with your idle when extra loads are on.

 

That looped coolant hose to the BAC valve is doing nothing. (As stated above.) The function of that metal tube piece on the side of the BACV is to warm it up with the hot coolant/water that runs through it. It transfers coolant/water from one hose to the other. Since you probably have the associated nipples capped off, you can just take the two screws out of that metal tube piece on the side of the BACV and remove it.

Change the fuel filter and the intank filter or "fuel sock" on the fuel pump.

 

^Mmm, good point. I too have hesitation, but only when im drifting with less than half a tank of gas. How would that effect the idle when it's warm though?

 

I am advising to change the fuel filter and fuel sock because of the 4,000 RPM hesitation he is having.


The poor idle probably has to do with an improperly set or malfunctioning TPS. The OP claims that he "played around with the tps while it was idling and it did not seem to help"...

This is how to PROPERLY set your TPS...

With key to "ON"... Car not running.

 

Ah gotcha.

 

are you jumping the initial set coupler when you set the TPS?
Where's Satch when ya need him?..hhaha!

 

what the hell is the initial set coupler... guess its searching time. I just warm up the car and turn the key to on and set it.

5 mins later....

Ok so green dual connector by the leading coil. just bridge the two connections then proceed to adjust tps?

 

No. Do not jumper the initial set coupler while adjusting the TPS.

 

Well my cars idle is pretty solid now. just replaced my fuel filter and did the variable resistor/set coupler trick. , not sure where to get a sock for the fuel pump locally, but I will drive it tommorow and see if it still has the 4k hesitation.

 

first put a damn shroud on the radiator. next, check your boost or pressure sensor. next, check your injectors.

 

lemme know where you get the sock from, i have no clue where to get one either lol

 

Rock Auto: S4 Fuel Pump Strainer

eBay search: RX7 Fuel Sock