It's been a while but my idle problem can't be fixed, It's been almost a year and I can't seem to figure it out. The mechanic I took it to replaced the throttle body and IACV, he also messed with the throttle screw and the car never idled the same ever since. The idle goes up to around 1300 RPM in gear (Auto tranny) and will surge sometimes in park or neutral, I noticed I can make it surge by moving the wheel, or turning on the A/C. Before the throttle needed to be kept open a bit so the engine won't stall out. If it was closed the engine would die out coming to a stop. I did a head gasket 2 weeks ago and timing was off so now the throttle is closed but that high idle is still there, also put in new intake manifold gaskets. I noticed all this happened after he replaced the throttle body last May. I got it used on eBay. Earlier I tested the voltage for the TPS and it was around 0.63 closed and 4.65 WOT, the cable is not tight and i can hear the throttle close, but is it possible somehow the butterfly is somehow a tiny bit open? Also I unplugged the TPS and got no CEL, put it into gear to see if it changed anything and the CEL never came on. Here's a video if it acting up.
https://www.youtube.com/watch?v=V8Pj...ature=youtu.be

 

Your TPS is not properly calibrated it should be 0.5V at idle and WOT is 4.5V, or if you have an obd2 scan tool plug it in and go to live data and go dow to TPS% it should be adjusted to 9.0%. ALso have you checked all your vacuum lines and I would leave the idle adjustment screw alone for now, that really is not your issue at the moment unless its adjusted all the way out or in.

 

Vacuum lines are where they need to be at, I checked them and they all seem good, no cracks at all and they are all nice and tight. Okay I will try to adjust the TPS and go from there. It looks like It's still the OEM TPS and never has been disturbed. I will see what happens.

 

Trust me it doesn't matter if its the oem TPS or a new aftermarket one on there it has been touched or is out of spec the numbers you got prove so. Just adjust it and see what happens, I remember when I worked at a shop and an Integra came in and the car was running, but running so poorly and it was just his TPS being out of spec that caused all his issues. I am also assuming that your throttle body has an FITV on the base of it and lines running to it? If so try cleaning that valve and see if your idle improves, may just be dirty in there.

 

First things first. You need your base idle to be able to get down to 500+-50rpms, which is that white line in the middle of 0 and 1000. If you can't do that, you won't be able to get your idle correct. So start there and go from there.

Warm the car up all the way. Turn it off, disconnect the iacv. Start the car, it should act like it's going to die, but it won't. See if the idle drops to that line. If not, then you need to need to turn the idle adjust screw clockwise so the idle drops to that line. If not, then you either have a vacuum leak, the iacv is bad, or the butterfly isn't closing, most likely because he screwed with the throttle stop screw, which is set by the factory and should never ever be touched. It's also possible the throttle cable is keeping the butterfly open, but you said there is slack so probably not.

If you can't get the idle down to that then you need to plug up the iacv port on the throttle body. If you can get the car to die then the butterfly should be closing properly. There are two ports, just get some very strong packaging tape and cover both up good so you know nothing is getting through. If you can't get the car to die then there is a vacuum leak, the iacv is bad, or the butterfly is open.

The idle adjust screw is at the top of the throttle body facing the passenger side, the throttle stop screw is what stops the butterfly from closing. They are totally different and have different purposes so don't mess them up.

At that point, report back here what's going on.

 

Random question: don't preludes idle at 750? I've had four 4th gens, all idled at 750. Or it's different for 5th gens?

Edit: helms says 750 idle. And furthermore, most cars idle at 750 from what I just saw on google.

 

Yes your right my lude has always idled at 750rpm. 500 to 550rpm would be too low almost chugging along.

 

Back, with the engine at temp there is no air being sucked in, now I unplugged the IACV and the engine started to surge between 1100 RPM to 1300 rather quicky, the engine didn't stall at all. While it was doing this I turned the idle adjusting screw and made no difference. I had a new aftermarket IACV installed on there, but when I did the HG I put the OEM one I got on eBay and they are both working. Since the same symptoms appear with either IACV so I'm assuming they're fine. Before the HG job I found no leaks by spraying carb cleaner all around the intake manifold. I put new gaskets in and they aren't leaking at all. I'm starting to think it might be something with that throttle stop screw, should I try a different throttle body?

 

You can easily adjust your throttle stop screw its the little allen screw with a 10mm nut on it, kind of a pain to get to when the throttle body is mounted on the intake manifold but just be patient if you want to do it this way. And it for sure has nothing to do with your IACV just leave that alone those things don't really go bad that often. I would say it has to be a vacuum line or your tps is still not properly calibrated. Have you adjusted your valves at all?

 

I'm worried, I am new to forums, so I don't know the proper etiquette. But I have a 95 lude bb1 and I'm having a weird idle problem like a lot of people do but mine idles super low at normal and cold temperatures.and when I put it in gear it kinda is lurchy until higher rpms..but I can't find a vaccum leaks.. And someone told me that I don't have a fitv..please help!!! I just bought this and hope its not another Dsm experience. Can I drive it like this to get it to my shop?? It was running just fine but then when I go to start it maybe 2 hrs later it started doing this..it used to idle at 1500 all the time_but now it surges from 750 to 1200

 

Your car shouldnt ever idle at 1500 rpm when its warmed up or are you talking about when its cold upon starting and it just idling at 1500rpm like how it should normally? Sounds like you need to check your lines going into your throttle body and make sure they are hooked up to the right spots if you are missing your fitv. Also try cleaning your idle air control valve and see if that helps any if not you may beed to replace it sometime soon.

 

I had a good look at it and I noticed the yellow paint on it seems untouched, but idk. Valves are adjusted, but the valvetrain is still noisy no matter what I do, when I did the head the cam caps and rockers and lobes don't have or very minimal scratches, last owner said it was a new head so maybe that's why, for a 211,000 engine with 170 PSI of compression across the engine runs rough, sounds unhealthy, and makes minimal power. Timing is good now but the engine isn't making power, never has, anyways, I'm gonna try calibrating the TPS next, BTW I was planning on replacing this engine with a H23 from Hmotors around August, but since I can't wait I'm gonna be swapping it out mid next month . I'm gonna still try to fix the idle problem, mainly cause Imma have to smog it and idk if that will make me fail. I'm gonna be selling the head since it's in good condition, had a pressure checked and resurfaced. But TPS next and we'll see.

 

Well you should pass smog no problems the higher idle wont be an issue they are just testing your emissions and your not throwing any check engine light codes so you are good to go.

 

Nice. It's not overheating anymore, so I think it should be good then. I have a CEL code tho, when I went to disconnect the Knock Sensor it broke, I got an aftermarket one that I have yet to put on. Still gonna try to fix the problem, lol. I want to know what is the issue

 

The knock sensor should take you about 10 minutes to install super easy.

 

I alright so, i pulled out the fitv and cleaned it. Now i dont know how far to screw it back in! Please help

 

So i replaced my fitv with a new one and i cpeaned my iac valve and it still stutters when i drive it at low rpms

 

If your screwed in the idle adjust screw all the way and it still didn't get lower then your iacv is either bad or you have a vacuum leak somewhere around the intake, especially since you said the factory yellow paint in your throttle stop screw has been untouched. Since you said you have tried two iacvs and the problem is still there suggests that the iacv isn't the problem.

Your tps isn't really that much out of calibration but even if it is out of calibration, that would cause your idle to drop lower than spec, not be higher.

Now you just gotta find the vacuum leak. It could be a hose, as gasket(throttle body, intake manifold), anywhere on the intake side.

Once you find and fix the vacuum leak you can go back and adjust your base idle as I suggested.

All of this assumes your fitv is working properly and you've already opened it up and turned the plastic piece down til it's snug.

 

I'm gonna look into the vacuum leak tomorrow and see what I find. I replaced all the intake gaskets when I did the head gasket since I had everything opened, they didn't seem to leak before (sprayed carb cleaner on intake side) what's weird is that if im not pressing the gas the car will still go and shift on its own to 2nd gear, could be cause the high idle tho, but whats interesting is before when it surges i could hear a pop coming from the intake itself, when the car is at temp and im cruising lets say in a parking lot ill be pressing the gas and ill be at almost 2k rpm and if i let go of the gas i can hear that "pop" noise from my intake and the rpm's will drop to like 1k, then the idle will quickly rise to 1400 again and its really annoying. i dont think its the tranny shifting cause you can feel when the tranny shifts. you can be right about the vacuum leak cause the porcelain on the plugs are white like snow and the ring is really black, i cleaned the pistons when i did the hg and theyre black again lol

 

I would run a compression test to just check the sealing of the head gasket, assuming you haven't yet.

 

Still 170 PSI across at temp, 165 on a lukewarm engine.

 

Is the high idle happening when the car is cold ? Cause thats what its supposed to do.

 

Cold or Hot, it would idle normally in park or reverse at around 1k RPM or lower, but as soon as you pop it into drive or reverse the idle kicks to 1400 only in gear, when put into park or neutral the rpms wouls shoot up then go down to 1k, sometimes it will stay or sometimes it would surge then calm itself.

 

Have you tightened down your fitv yet or not ?

 

I haven't had time, I'm gonna do it tomorrow for sure so by tomorrow night I'll report back.