I assume that is the proper term for the flat head 'valve' located on the throttle body. I'm guessing it controls idle. Here is my plan-
Allow the car to come to full warm idle, which will no doubt be 'erratic' and loping.
Mark where the screw is now.
Turn it up to 180 degrees to the right slowly, noting the changes
Turn it up to 180 degrees past where it was to the left and note changes.

If this does not fix the idle problem. . . which sensor should I change next?

Not that it matters too much, but this is a 92DX auto which was swapped to a D16Z6 (I believe, because there is a VTEC selinoid, and there is also a MAP sensor on the throttle body and one mounted to the firewall) but the ECU wasn't swapped, so it is still DX mapped. I don't happen to have the 'book' here to determine the order of the change chain so help me out here.
Thanks
B

 

brian,

just a thought, but it could be a vac leak. are there any hoses off/cracked?

good luck.

you still got your si? i haven't seen you around for awhile.

 

Whats up man? Not sure who you are but I didn't look at your profile or anything. I don't have the 99 Si anymore but I use this name on like 3 or 4 other sites so I'm staying consistant. I haven't been around much because I haven't had my license in like 4 years so I've been veery careful. I get it back in May so especially now.
I have checked the vac lines and didn't see anything. I could replace them all cheaply I suppose rather than going elsewhere.

 

why no license?..........was the si too fast?


this is shawn...........went to school w/ you back in the day.....used to see you at damons when you worked there.....


Modified by thelate1 at 4:05 AM 1/8/2006

 

Remove the IAC valve and clean it with choke cleaner.(If that model has one) Warm the car up and unplug the connector to the IACV. Adjust the idle to between 450 and 550 RPM. Plug the connector back in and clear the codes. If the idle is still eratic....... Does that model have a Fast Idle valve. If it does, open it up and make sure the donut that surrounds the thimble is completely seated. Sometimes it gets unscrewed. Eratic idle happens when the ECT sensor says the engine is warm and the RPM is over 1100 and the throttle plate is closed. The ECU cuts off the fuel injectors, the RPM falls, the injectors cut back on, and the process starts all over again. It can be caused by anything that allows air into the combustion; IACV, FITV, vacuum leak, excessive idle screw bleed, or misadjusted TPS.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by amckee &raquo;</TD></TR><TR><TD CLASS="quote">Remove the IAC valve and clean it with choke cleaner.(If that model has one) Warm the car up and unplug the connector to the IACV. Adjust the idle to between 450 and 550 RPM. Plug the connector back in and clear the codes. If the idle is still eratic....... Does that model have a Fast Idle valve. If it does, open it up and make sure the donut that surrounds the thimble is completely seated. Sometimes it gets unscrewed. Eratic idle happens when the ECT sensor says the engine is warm and the RPM is over 1100 and the throttle plate is closed. The ECU cuts off the fuel injectors, the RPM falls, the injectors cut back on, and the process starts all over again. It can be caused by anything that allows air into the combustion; IACV, FITV, vacuum leak, excessive idle screw bleed, or misadjusted TPS. </TD></TR></TABLE>

Ok. I will do the IAC valve when I have a new washer/gasket jaunt to put in there. I'm sure it's a $2 part but feel it'd be best to replace to be sure.
The fast idle valve- is that the valve on the bottom of the TB that just has 2 coolant lines but no electrical con.?

I checked the vac lines by running my hands over them while the car was having the problems. I couldn't feel anything. I wrapped my palms around the lines to try to seal a potential leak. I removed the brake booster line and plugged the vac port with my thumb to rule out that hose. I disconnected other vac lines 1 at a time except for FPR of course, but that one is so short I feel confident I eliminated that as a possibility.

The spark plugs were just beyond hand tight. I didn't need the ratchet to remove 2 of them. I removed and checked and they looked new. I replaced the cap/rotor because it was in shitty condition. The car started and had power like normal but of course the lope idle persists.

I don't think the idle screw is a factor because there is some gunk infront of it, as if someone JBwelded it into place, but it's a softer material, like dry cake icing.

I also don't think the TPS is out of adjustment as it still has the factory rivets, shows no signs of trauma, and responds to throttle inputs as it should. I believe it is the IAC because when cold, it idles high, until warm or until you 'blip' the throttle. Then the lope starts. It reminds me of this one DSM that did it and the guy said something about the O2 sensor and closed loop but I don't pay DSM people alot of attention.

I guess I'll tackle that IACV w/o disconnecting the coolant lines? Just spray the thimble with some choke cleaner shiznit, let it drip down? Word. I'll go there and post back.

 

hmmm. I never worked at Damons. Only place I worked at in Park City was GAP and that was back in the 90's. hmmm what car did you have when I had the Si? And I lost my license in a long story situation. Basically, took the Si off the road for the winter due to blown engine. Replaced engine, got it running the same day my ex-gf ran a light, got t-boned, totaled her car. I had to start driving right away- no problem except no insurance. I just forgot to add it in the whole situation. Wouldn't be a problem except I did get stopped. Lost license for that, kept driving, got caught 2 times, and now here we are. I haven't been pulled over in 2 years and 10 days, so I'm nearing the end of my sentance. WORD!
B

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thelate1 &raquo;</TD></TR><TR><TD CLASS="quote">why no license?..........was the si too fast?


this is shawn...........went to school w/ you back in the day.....used to see you at damons when you worked there.....


Modified by thelate1 at 4:05 AM 1/8/2006</TD></TR></TABLE>

 

Fast idle valve is on the same side(front) of the plenum as the IACV. It has a small coolant line but no vacuum line. The IACV seal is oring style. It won't break when you remove it if you want to go ahead and do it. It is a cheap part, but my Honda dealer had to order all of those little seals on the TB. You probobly need to disconnect the coolant lines on the IACV because you may have to remove the screen to get all the deposits from behind it. That plug in the idle screw is the factory seal. Do everything else first, one thing at a time until you find the problem. Nothing is worse than doing too many things at once and not knowing exactly what fixed it. If you have the factory seal, you probably won't have to touch the idle.

 

ok. in this pic, you can see the IAC and the throttle body. I'm assuming the TB is where the fast idle valve is, correct?



B