I actually have a small issue with my cars idle. Last fall I did a JDM motor swap in my 1993 Canadian FD, I got the motor from a guy who was doing a V8 swap and the engine ran fine for him. I hooked everything up properly and the car runs perfectly fine accept at idle. It sits at around 1500rpm. I sprayed some WD40 around the intake manifold to see if the idle would change but nothing so i don't think its leaking there. I also played with the throtle settings and 1500 is the best idle I can get from it. If I unplug the vacume line from the boost sensor the idle drops to about 500 rpm and is really rough. Does anyone have any theories what I can check or replace? Could a faulty one way check valve have wrecked my boost sensor? I'm running a pettit unlimited ecu. thanks for any help you can provide.

 

Check your idle position sensor.

 

Only place you should adjust idle is the air valve at the bottom of the TB ( below the elbow).

 

whats the idle position sensor, and where do i find it? The air valve your talking about is the screw in the TB at the bottom, correct?

 

Yes, turn it in for a lower rpm, if that doesn't work you have other issues.

 

I will dig into that tomorrow afternoon if time allows. If this does not work can you give me some clues as to what else it could be. thankyou for the information so far.

 

Something else to check is the throttle cable tension. With the swap, there is a chance that the two nuts may not be in the right position along the threads to allow the cable to return to a slack condition with the throttle in the idle position. There shouldn't be any tension on the cable at idle. Also, a slight vacuum leak will bump the idle up slightly, but if the leak is significant the idle quality will be low and lumpy. Try to think of what was removed and reinstalled on the engine during the swap as that normally helps you to logically rule things out.

 

ok, i checked the tension on the trottle cable and then loosened it slightly and got it down to aprox 1300rpm.

the screw in the TB was in all the way so something else must be wrong. So I played around a little bit. I noticed the one way check valve between the boost sensor and the tb was allowing air both ways. When i put a good kink in the hose to stop the suction on the boost sensor the idle went super low and horible. As i unturned the screw in the TB with the hose kinked the idle would get better and I belive I could get it just right by doing this. Before i do this I would need to get myself a new one way check valve. Is this proper? Or is there something else wrong. If this is correct what is the idle speed I should be aiming for??

Thankyou everyone for all the help so far.

 

By squeezing the map sensor line, your making the computer think it doesn't have vacuum so it would add more fuel making your car run rich, which would bring down the idle because the car barely wants to run. I don't think its that.

Have you tried your idle adjustment screw?



thewird

 

It's not a check valve ---it's a filter.I would suggest that you download the FSM section dealing with setting the idle and just go thru the procedure.

 

I stil have to try the fsm, which is what i'm giong to do right away. I have already tried that idle adjust screw in the picture. I was reading some other threads I ran across and I ended up unpluging a cylinder shapped item along the back of the throttle body. I saw the letters bavc or it could have been bacv writen on it. The idle dropped to 1100ish rpm. No check engine light came on when that was unplugged. I noticed that when I start the car the rpm sits around 800 to 900 until i give it throttle, when the needle drops back down it sits around 1100. I'm just trying to give as much info from my trials as i can.

 

Could be the fast idle cam is not disengaging when engine warms up--due to improper adjustment or the thermowax is caput.All covered in FSM.

 

I'm going away for a week for work so i'm putting this on hold for a little bit, when I get back next week i'm going to continue work on it. I'll post more once I know more. thankyou so much so far for the help.

 

ok, my idle is now doing good. I believe there was a number of problems with my car. I'll explain. I descided when I got home from being away that I might as well replace the injectors and replace the rats nest with another one I rebuilt. None of that fixed the idle so I knew for certain there was no leaks except maybe the LIM. I noticed the TPS was turned as far as it could go the one way so I turned the oposite and made the cars idle bounce up and down. This also made acceleration horrible in the low end. I unplugged the AWS( i think thats what it was) and the idle dropped to around 500rpm. I adjusted the little screw in the TB until I was around 800 to 1000rpm. The needle was bouncing away again and I adjusted TPS back to its original position. The idle increased to aboiut 1300 1400 rpm again. In small increments I adjusted the TPS back again until the idle dropped to about 800 to 1000 rpm without any bounce. Now I have generally smooth throttle response.

I don't know if this is related but when i let go of the accelerator while in gear the car has a slight jerking motion as it slows down. While tightening the TPS once I was done adjustments I accidently snapped off one of the screws some how. I thinik the other one should hold it for now, next time I pull off the TB i'll drill it out.

 

Thankyou everyone who gave me a helping hand in this matter. I greatly appreciate all of the input.

Another thing i noticed is my turbos sometimes don't kick in until over 4000rpm. The part that I don't understand is they usually work fine and then sometimes this happens.

 

4000-5000 RPM is transition so if you go WOT between that, they may not spool right away. My BNR's did the same thing. You learn to drive around it.

thewird