Rough Idle, Stalling

[darbyhouse]

Howdy All,

First post to this forum.

I have a 1993 Prelude Si, 140K miles.

Recently the wife decided to take the car on a 1/2 trip....my luck, the timing belt went, the car obviously died...she pulled over, tried to start it again and again. Well, as Im sure you have figured out, most of the valves were bent. I had the timing belt, valves replaced, head cut, new water pump, rotor, plug wires, etc. At $1800 after all work, we were good to go.

The car started to idle quite rough. I was thinking it was the timing. Took it back to the garage, explained what was going on. They said it should take a bit to "break in". Here I am, couple hundred miles later, and the problem has gotten worse. Run great once you are rolling, but coming up on a red light after higher revs, it would bounce around between 100-700 rpm.

So, Ive been searching through this forum, identified a potential solution with cleaning out the IAC. The screen was totally clogged. Cleaned it with Carb cleaner and reinstalled, reconnected the battery.

Started it up (had not been running today), the idle was up to around 1200-1300, idling fine. Got it out for a test drive....went about a mile, turned into a parking lot and now it totally stalls, every tiime.

All vacuum hoses are connected securely. PCV is clean (replaced it recently).

So, not sure where to go from here. Any thoughts?

Im pretty good under the hood (replaced the stock lower intake with a Motordyne MREV2 and installed a 5/16" spacer on my '04 350Z Roadster...running great).

Help.

:confused: :confused:

Thanks all.


Mike D.
Houston TX (Galleria)

[darbyhouse]

Update....playing around with the throttle body. There is a small hose which connects to the very center of the body...when I disconnect that hose while engine running, it smoothes out. When I cover the hole, the idle goes rough again.

Not sure what that connection does and will it hurt to leave that hose disconnected.

Thoughts?


Mike .

[darbyhouse]

Last post....experimenting as I go. Was just idling the engine without the hose on, let it get up to temp...covered up the same hole, and it stalled immediately. When not covered or the hose connected, idles fine.

Not sure what that vacuum inlet is for.

Thanks again.

Mike D.

[Eric]

just **** with it my friend had the same prob

[darbyhouse]

....I did, and runs alot better. But the hose is disconnected....want to know what that is for so I dont **** something else up down the line.

[Prelude13]

That's your PCV line and PCV valve.

http://upload.wikimedia.org/wikipedia/en/c/c3/Pcv_valve_1.jpg

You need to replace it(again) and then adjust your idle screw manually(if you have to). The proper idle is 800+/- 50, located on the inner side of your hood.

and yes, it's highly suggested that you have a fully functioning pcv system.

good luck!

[Q7prelude]

where is the idle screw?

[darbyhouse]

Thanks for the feedback Prelude13...however, the PCV valve is still connected....Im attaching another pic....the white circle is the PCV valve connection, the white circle is what Im asking about....thoughts?

[darbyhouse]

Sorry....RED circle is the one Im asking about....

[Prelude13]

I dont know exactly what that line is, the one circled in red.
It could be a line that goes to your FIV-fast idle valve.

http://mustardcat.brinkster.net/p3g/CommonProblemFixes/Bouncyidle/bouncyidle.htm

check that out, see if you can mod the FIV a little to make your idle nightmare go away...

good luck.

[darbyhouse]

Thanks much for the feedback. I had read through the link you sent a few days ago. There is a type of valve or something further down the hose; I have a feeling it is due to that. I may try to take it off and see what it does....not too sure.

[darbyhouse]

Actually, if you look at the last pic with the red and white circles, Im referring to the "valve" at the bottom middle of the pic connected to the hose. That hose is what Ive disconnected from the TB.

Thought?

[Prelude13]

Im just curious, does/has the car ever idle properly at 850-900ish?

also, get a better, clearer pic of what you actually disconnected.

:cool:


oh, and check for proper coolant levels since you've cleaned out the IAC before...

[darbyhouse]

Yep, definitely used to idle once up to temp around 700-800 before the valves being replaced with the cut head, water pump, etc.

Now having taken off that hose, it runs 1800 or so when cold, comes down to about 1000 after warming up. The coolant level is topped off.

The cam battery is charging now...will post a few more clearer pics shortly...took the first ones with my PDA.

thanks Chief.

Mike D Houston

[Prelude13]

Okay sounds good, you know where your idle screw is right?

[darbyhouse]

It's the gold hex screw on the side of the IAC, yes?

[darbyhouse]

Here are a few more pics...much easier to see than the first ones. Throwing one in of my 350Z Roadster as well...put a CAI, Voltage / Grounding Kit on, Motordyne MREV2 lower plenum intake and spacer...all added about 15whp.

Anyway, let me know what you think.

Thanks much for your time.

Mike D Houston

[Prelude13]

Oh wow, i really dont know what that line is for...

If you havent already, here is the online manual for you to download.
http://downloads.hondatech.info/Auto/Manuals/Prelude/Prelude%204/Ab0VE.Honda%20Prelude%20%2893%29%20Service%20Manua l.zip

I mean, your idling problem shouldn't be fixed to that one unhooked inlet/line.
You're not throwing any codes right? we can rule out a bad o2 sensor. . .or not? :confused:

check out your FIV(fast intake valve).



ps. your Z is SEXAY!!

[darbyhouse]

Nope, no codes (unless the CEL bulb is burned out).

I'll download the manual (thanks for the link) and see what that vacuum line is for. Yeah, doesnt make sense, but is working without problems at the moment.

The Z....yeah, Im diggin it....doesnt leave the garage much...the Honda is my daily driving vehicle.

I'll keep you posted on my progress.

Thanks much Chief.


Mike D. Houston

[darbyhouse]

Did some digging into that manual....that TB vacuum inlet is for the fuel pressure regulator....this may explain the rough idle and constant up and down of the rpms.

Going to replace it this afternoon.


Mike

[darbyhouse]

Last post....two primary causes I found to be the problems:

1) The fuel pressure regulator was bad.
2) Found a vacuum hose loose.
2) There is a very small filter which goes between the FPR and the fuel injection fuel bar...seems when the garage did the valve job, they didnt reinstall this item. I found it wedged below the TB.

Anyway, that's it. For whatever this post is worth to anyone.

Thanks.


Mike D houston

[chodecz]

Thanks for your help guys,.