Okay, my car runs fine when cranking up and idling by itself for a really long time... the only time that it actually stalls is if I drive about 25+ miles and once I come to a stop if I dont have the a/c on the car dies and keeps doing it til car is cool again(turned off for a while. I have already cleaned the IACV and yes it was very dirty btw and ran seafoam treatment. My temp gauge is nice and where it needs to be too. NO CEL's

I will say this, I still have not put in the throttle stop screw that I got off of the y7 throttle body (mine was missing) a long time ago and have a feeling that this may have something to do with it so I will put this on tonight but its a pita to check because I have to drive far to get the car to start stalling again once its cool... Truthfully I almost want to say that cleaning the IACV almost made it worse but I dont want to guarantee that.

Also upon last inspection of the throttle body, the plate was really black and thick also when I took off the IACV the inside of the intake manifold was just as black... could this have something to do with this as well?

Also on the throttle stop screw, since mine is gone how I gauge the adjustment... They say NEVER mess with these screws but I dont have a choice and cant find a writeup.

 

1) You may need to replace the throttle. Try getting a replacement at a junk yard.

2) Regarding the low idle and black soot, are you regularly changing the engine oil? Have you tried replacing the PCV valve?

3) Regarding the low idle and IACV, if you disconnect the IACV connector while the engine is idling, does the idle speed increase? If not, you should replace the IACV.

 

1. Can it be cleaned? Or are you referring to the lost screw?

2. Regularly changed oil Supersyn mobil 1 if that makes a difference, + have not tried replacing pcv valve yet (where is it located?)

3. I need to do that test...just to be prepared it will throw cel when I pull IACV plug right?

1 more thing, I changed the TPS a while back... could this be causing it too? Drilled the old one out and put new bolts in...

 

1. You can clean the throttle body, but you need to properly install a stop screw or replace the throttle body.

2. The location of the PCV valve differs depending on year/engine.

3. Yes it will throw an IACV code, so afterwards clear the code from the ECU (remove 7.5A BACKUP fuse for about 1 minute).

4. Was the new TPS calibrated after installation? (= ~0.5V closed, ~4.5V WOT)

 

1. I have the y7 stock screw... it should have enough clearance and is the right setup for the y8 right?... little allen plus nut.

2.1998 D16y8 Coupe (ex)

3. thanks I hope I dont need new IACV I will be pissed its expensive!

4. must check (what wires am I tapping into to measure this do you have the colors or is this trial and error?)

 

1. It may not be that simple. The stop screw is adjusted at the factory.

2. Put the front end on stands. Reach your hand above the oil filter and follow the PCV rubber hose to the oil breather chamber where the PCV valve is inserted into a rubber grommet.

4. One way is to back probe ECU connector D:

 

Thanks Ronj... I will do this when I get home tonight...do I need to test TPS while car is running or car off with ignition on, or car off with ignition off? Just making sure, I have a very small window to do this in.

 

Turn the key to ON(II) without the engine running.

 

Adjust the stop screw so the throttle plate just closes fully, but does not slam against the sides of the throttle body.

Then, be sure to calibrate your TPS before doing anything else. You can also test at the center wire of the TPS under the hood. Like Ron said, turn the key on to power up the ECU and sensors, but do not start the engine.

With the IACV disconnected, rpm should decrease but the engine should not quite stall. While fully warmed up, adjust the air screw (not the stop screw) to get about 400 rpm with the IACV wire disconnected. In other words barely running but not stalling.

If you still have stalling issues you could try opening the air screw a little more. You just can't have it go over 750 rpm on air from the screw alone, as the ECU would not be able to slow it down and you will get a CEL.

 

Using this method, I think you need to back probe the TPS connector middle wire with the + voltmeter probe and ground the - voltmeter probe to the engine. Mk, please correct me if I'm wrong.