AudioFunk

I have a 1994 Prelude Si and I've always had an idle problem with it, long story short when I bought it the idle was rough but it was fine. Then I got a bouncy tach, was caused by a loose ground, but before I found that out I had my front neighbor try to diagnose it, he said it was my TPS, me knowing nothing about engines I said ok, we got one off a junkyard accord and put it on, no change, lol he also messed up my mechanical timing, by the time got there the car was running, I also cleaned my IACV. By the time he left it wasn't. Few weeks later my timing was fixed, but I noticed my idle was rougher, once at operating temperature the idle would be low in drive and reverse and stall once coming to a stop. Idle would also go down and up like this . The car idled better when the alternator was unplugged, and when the TPS was unplugged. I decided to put the old TPS on, I put it on and calibrated it. Idle was still rough but didn't go up or down like in the video, but still low and still stalled, but it took longer. Water pump started to leak, so I changed that and the timing belt. Before I had it changed I noticed a hesitation from a stop that wasn't there before, I would press the gas and the car just felt sluggish, the RPM's would climb a bit but no power. It does it more taking off from a stop or at low speeds. After the big job my car had more power, but the idle was crappy would die coming to a stop, unplugged the TPS and it didn't stall but didn't let me go pass 3k RPM and 40 MPH. So my mechanic adjusted the throttle cable so it would stay open. Idles at 1200. Then he told me to change my throttle body, Got a used OEM one put it on and this time the car wouldn't start when the throttle was closed, when it did start you have to give it gas, so once again throttle was held open car would stay on but had really bad hesitation and engine kept going forward at idle, he said my IACV was bad, I got a OEM used one, Denso. He put it on, but I noticed he still kept the throttle open, I'm guessing it won't idle with it closed or it's rough as hell? I still have the sluggish hesitation and now it does it around the 2500k-3000k RPM and low speeds/taking off from a stop, it would be sluggish then the car would just accelerate fast. Happens on all gears. When it park or neutral the idle would be low, then when I pop it in Reverse or Drive I can hear my CAI sucking in air and the idle would rise to 1300 or 1400. I'm stumped, no CEL. I wanna test the MAP sensor but I doubt it's bad since I have no CEL, but any ideas? New Throtte body and IACV and still won't idle right. The hesitation started before the timing belt change so I doubt it's a timing issue. Ignition timing is okay, I have more power now than before the timing belt change due to mechanical timing being of. I think the problem is something else that is also causing it not to idle correctly right? Will check my vacuum lines tomorrow but I will appreciate some input till then. Btw I forgot to add the hesitation I felt before the timing belt change when my throttle still idled with the throttle closed was worse when the IACV was bad and the throttle was kept open.

Sparksman

Off the top of my head I think this is all that can effect idle, I may be forgetting something;

- Ignition timing "make sure to jump service plug when doing"
- IACV "can be cleaned/replaced"
-FITV "can be cleaned/replace"
-MAP "can be cleaned/replaced"
-O2' sensor "can be cleaned/replaced"
-TPS "requires calibrating"
-EGR "cleaned replaced"
-EGR ports "cleaned"

Other possibilities;

- Clogged secondary fuel filter
- Injector(s) clogged or getting stuck open/closed
- Vacuum leak on intake manifold gasket
- Vacuum leak else where
- Idle screw has been turned too much
- Tune/injectors "never mind if stock ECU and stock injectors"

Im not sure what else to say other then give suggestions. Its incredibly hard to pin point a problem over the internet.

AudioFunk

True, but from the list you typed I can cross out a few. IACV replaced cause it failed, Throttle body replaced with a known working OEM unit, so new TPS, new FITV, and idle screw set, sprayed water over intake manifold no sign of a vacuum leak, but last checked 2 months ago, will double check tomorrow with Carb cleaner. Ignition timing set, service connector jumped while setting timing, Mechanical timing set correctly, have more power after the timing belt change, will run injector cleaner. Haven't checked EGR, O2, And MAP. No CEL. Oh and I have new NGK plugs, new NGK wires, and the whole distributor is less than a year old. Compression 175 on all 4.

holmesnmanny

No offense, but your mechanic is really bad. I would stop going to him.

Put the throttle back to oem specs, which is slightly a little slack in the cable.

If it was me I would first drop in a Denso oxygen sensor if you can't even remember the last time it was replaced. If you want, you can pull the oxygen sensor connector and let it throw a code and see if it idles better. If it does, you know the sensor is bad.

It can't be clogged egr ports since the egr doesn't work at idle.

You can check base idle by pulling the iacv connector and seeing what the idle looks like. It should be between 500-600. Keep in mind the first big line after 0 is 500 not 200 rpms.

AudioFunk

When checking base idle does it have to be in Park or Drive?

AudioFunk

So I checked for vacuum leaks and found nothing, but when I took off the distributor cap I noticed the rotor tip was like burnt, so I took it off and I noticed a red coppery powder on back of the rotor and on the plastic shield behind it, I had a spare cap and rotor and I put those on and the hesitation went away I drove it with no problem. The back of the dizzy where the ICM is I didn't notice the red powdery stuff. I bought the dizzy at autozone you guys think I should replace it? I have warranty on it. Anyways, I closed the throttle and reset the ECU, then I started the car, the idle is low and rough, then as soon as I rev the engine the car stalls, here I have a video. I noticed It's the same even after the IACV was replaced. I don't know where to look anymore. I'm gonna test the O2 tomorrow. https://www.youtube.com/watch?v=Pg8i...ature=youtu.be

AudioFunk

Some Notes. Idk what he did to mine but It's really unfortunate what happened to me, I took it in for a timing belt change, before the job the car would idle normally, it would be rough and low that it wants to stall once at operating temp, then I come back for it and the throttle is kept open, I close it to find out the engine idles really rough and shakes like hell, and stalls coming to stops, but smooth above 1300 RPM or so, engine has more power after the TB change. I take him a used throttle body cause he said that's why it died, I come back after he put it on and It's even worse! Hesitation, Sluggish acceleration, etc. I closed the throttle and it wouldn't start, tried again it started but stalls right out unless you keep the foot on the gas, took him a used IACV cause he said it went bad, then I go back for it again and It's better but when the throttle is closed it would still die when revved and the idle would be low then stall. Idk if he messed something up cause before the TB change everything was fine.

AudioFunk

I tried my friends ECU, since we have the same car. And no change, when the throttle is closed the idle will stay steady, once it starts to warm up it will start to miss and the idle will start to surge, but when the IACV is unplugged the idle stops surging. I just replaced the damn thing. Also I can hear a pop coming from the intake after it surges, weird.