Prelude won’t idle

[Cris]

I read the troubleshooting page about how to solve an idle problem and I’m still stumped. I have a 1994 Prelude Si H23A1 Automatic and long story short, it has a problem with idling. So a while back I noticed a hesitation from a stop, the RPM’s would be sluggish then the car would pick up speed. My water pump started to leak, so I replaced it as well as the timing belt. Once back I noticed I had more power, later that night my idle got really rough, but ran great above 2k RPM. I noticed the mechanic left the throttle open to keep it from stalling, he told me to change the throttle body, so I got a used complete OEM one. So new TPS and FITV. The TPS was replaced before and had a rough idle and it would get low and stall once at operating temperature. Before the timing belt job it would idle rough and low, but after this it would idle really really rough, the tension on the belt is nice and tight, but not so tight, just right. After the new throttle body was installed, the car came out worse, more hesitation and sluggish acceleration. If the throttle plate is closed the car would die unless I give it gas, so it was kept open, he said my IACV was bad, so got a used OEM Denso unit. He put it on and lol throttle still needs to be kept open. It runs better but still has that sluggish acceleration throughout all the RPM ranges. Sometimes it would accelerate normal others sluggish. I noticed in park or neutral the idle would be like at 1k rpm, but as soon as I pop it in park or reverse I can hear my cold air intake sucking in the air and the idle climbs to 1300 or so and stays there. I know Eric you said if the ECU can’t see the TPS is closed it’s not a good thing, maybe my ECU needs to re learn to idle? I have no CEl I even jumped the connector and no codes. Btw before the timing belt change if my alternator was unplugged or the old TPS at idle it would idle smoother and the idle wouldn’t go down to almost stalling. I doubt my MAP sensor or O2 sensors are bad since I have no CEL. I will check for a vacuum leaks tomorrow since It’s been a month since I last checked them. But any advice?

Topic

[dan]

is your timing correct and all lined up correctly? vacuum leaks are one of the primary causes for bad idle, ill give you a video on that however usually that will set a MIL

does the car smell like its running rich or lean? is your KIA correctly installed?

does sound like a issue with something with a intake, i recommend checking for vacuum leaks first in this link is everything for checking vacuum leaks including a demonstration video.

i would also try unplugging the battery terminals too let the ECU reset, checking its voltage and connections while you are at it, so there is a difference when its cold and warm huh? does the temp gauge work ok?

http://www.ericthecarguy.com/faq/solving-automotive-idle-problems?start=1#LookforVacuumLeaks

[Cris]

Yeah, both mechanical and ignition timing are set. Actually I think it is running a bit rich, but not enough that I have black smoke coming out of the exhaust. Will do that, And It’s the same cold or warm. and my temp gauge is working, my car overheats 1 bar then goes back to normal, then back up 1 then back down, but air is bled and it seems it overheats cause my radiator is clogged, but it is working fine.

[dan]

so you are saying your temperature on your gauge goes up and down a notch? from the half way point of the gauge? does it say its overheating about a quarter or eight of the full temp or just a little bit?

[Cris]

My temp goes up a little then back down, then back up and repeat, about 15 min of driving, mostly at low speeds or at idle. [IMG]http://i58.tinypic.com/nld3iw.jpg[/IMG] The right gauge is the temp, It stays in the middle like it’s supposed to then it goes up 1 bar then back down. It needs to go up 2 more bars for it to overheat completely

[Cris]

It didn’t overheat as much before but now that’s It’s hot it overheats more. My radiator has dried coolant all over the top I need to replace it lol

[dan]

looks normal, looks like its staying near the half way point, once it starts heading towards 3/4 of the way up the gauge THEN i would be concerned about overheat, if you feel the radiator needs replaced because there is something wrong with it replace it… nothing too lose in my opinion if you want too.

[Cris]

I am, but tomorrow I will check the vacuum hoses. Maybe the mechanic took off a vacuum hose during the timing belt change and put it in the wrong place? Will re set the ECU and close the throttle and see.

[dan]

yep check for vacuum leaks and unplugged or broken vacuum hoses, do all that jazz first thats my recomednation

[Cris]

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.It’s not making any noise, yet. 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. https://www.youtube.com/watch?v=Pg8iZ6cKJmg&feature=youtu.be

[Scott Allen]

Regarding whether you should or shouldn’t replace the distributor, if Eric has taught me anything it’s that trying to diagnose around known problems doesn’t work very well. If the rotor tip is burnt and there’s red dust everywhere, it’s gotta go. If the idle is still bad after you replace it, go back to diagnosis being absolutely sure that the distributor doesn’t have anything to do with it.

Just my 2c.

[dan]

it sounds almost like you have a vacuum leak somewhere but it also could be the Cold air intake, also if the Throttle Position Sensor is bad it will do funny things like this too, a Throttle Position sensor is essentially a variable resistor, test the throttle position sensor again just in case but mostly check its connections since you have already replaced it, if its connections arent bad go from there.

[video]http://https://www.youtube.com/watch?v=7Gfn2l3uUFY[/video]

it could be the wiring too the sensor, check for corrosion at the connector for the throttle position sensor, broken wires, ect…

how did you test for vacuum leaks?

[Cris]

I sprayed around the intake manifold with water. I tested the TPS, it read about 0.5V closed and 4.5V Wide open. Which is what Honda calls for I think

[Cris]

I noticed if I the throttle is closed if I rev it you can hear a loud sucking noise, then stall. But since my car would only run with the throttle open all the time if I plug the IACV hole and let go same thing a loud sucking noise then the idle surges then comes back down, IACV was replaced and it seems my old one wasn’t probably bad after all since it’s pretty much the same symptoms

[dan]

testing for vacuum leaks try this method instead

[video]http://https://www.youtube.com/watch?v=9CPqbaSgcok[/video]

[EricTheCarGuy]

My opinion, your mechanic doesn’t have a clue. If you read the article as you state, one thing I mention is that the TPS rarely goes bad on Hondas and messing with them usually results in making things worse. I think I also mentioned that aftermarket distributors are a known problem. I think I also mentioned that adjusting the idle screw to correct an idle issue is also a common cause of issues like this. I also mentioned that idle problems after timing belt and water pump changes are often the result of air in the cooling system. In short, I believe I’ve covered many of the problems you mentioned.

I think you’re doing well by checking for vacuum leaks, but the truth is with all that misguided work you’ve mentioned you’re starting from scratch and having to go back to the basics before you can find the cause of the issue. You might want to read the article again because as I stated, many of the things you mentioned are already covered there.

http://www.ericthecarguy.com/faq/solving-automotive-idle-problems

Honestly, I’d recommend you take it to someone that knows Hondas. I would wager it would be money well spent over trying to solve this yourself. In many ways you’ve been handicapped by the work that’s already been done in my opinion.

Good luck (seriously) and keep us posted.

[Author]

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