Kimini, the Prelude mid-engine Mini is getting toward being done, I started it today after sitting more then a year. The cooling system was dry so that was filled, a possible hint, see below.

Background:
H22A1, 5-sp, no accessaries other than alternator. Stock P13 ECU, stock thermostat. No power steering, power brakes, no ELD or EGR.

The Problem(s):
Starts up and goes into fast cold-idle just fine at about 1100 rpm. First problem is idle speed never comes down, even after coolent temp is up around 200deg F. Second problem, it was idling fine (at 1100rpm) until coolant temp got to about 150deg. It then starts this odd fast/slow/fast/slow idle, where "fast" is around 1500rpm, and "slow" about 1100rpm, at about once a second. Unplugging the IAC valve stops the up/down cycling, and it returns to 1100rpm. Another way to "fix it" is, while it's doing this up/down thing, is to open the throttle just off idle, up to 2000rpm or so, then *very slowly* let it back down - the problem goes away. However if I pop the throttle and let it snap shut, it'll fall back to 1100rpm and immediately starts the up/down/up/down thing again. It's very touchy, almost always starting the up/down idle all by itself, but I can always make it stop for a little while by the above method.

I have the Helms manual but haven't figured it out yet. No engine codes other then "20" are shown, which is the ELD. I would think *maybe* that has something to do with it but would expect the ELD to cause the problem all the time.

Any guesses from the experts? Your help is greatly appreciated and will help me get her on the road sooner.

One more thing, the manual says the correct idle is 550rpm. Is that true as it seems rather slow. I did doubleheck that my SPA tach is set for a 4-cyl engine, which it is.


Modified by kb58 at 2:55 AM 2/28/2005


Modified by kb58 at 3:35 AM 2/28/2005

 

what is your engine managment and what thermostat are you using?

BTW: You and your project are a true inspiration!

 

Doh, and I tried hard to include everything.

Stock P13 ECU and stock thermostat. Everything is stock for that matter, only a few things removed.


Modified by kb58 at 2:39 AM 2/28/2005

 

Did some more reading. One thing that concerns me is since coolant is run through the two thermo switches, I'd expect the hoses to be hot, but they aren't... A clue maybe. I'm also reading that the Fast Idle Air Valve could be a culpert, but since the engine has very low miles on it, for the moment I suspect an air bubble maybe. Can air in the lines leading to it cause this problem?


Modified by kb58 at 3:34 AM 2/28/2005

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kb58 &raquo;</TD></TR><TR><TD CLASS="quote">Can air in the lines leading to it cause this problem?</TD></TR></TABLE>

Yes. I had a hard time bleeding my coolant because of the pitch of my motor and had similar idle problems until the coolant was completely bled.

it will also do that (on a d-series and probably all honda motors) if you are using an auto ecu. but i think it only starts after it's warm.

I also have this theory that IACV's and distributers go bad when they sit for long periods of time. it's just so common for IACV's and dist to fail weeks after you buy a motor.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kb58 &raquo;</TD></TR><TR><TD CLASS="quote">I'm also reading that the Fast Idle Air Valve could be a culpert,Modified by kb58 at 3:34 AM 2/28/2005</TD></TR></TABLE>

take any intake tube off. start it and get it to bounce. stick you finger over the hole at the bottom of the tb, if there is vacume/it stops jumping it may be broke.

 

The idle is very normal at 550. And depending on how long you let the car idle it prolly just did not warm up yet. Mine has allways taken a pretty long time to get up to temp. In the winter and i can let the car idle for 30 min and the car will still not come up off cold.

Good luck on your project! I look forward to reading you weekend progress EVERY monday morning!! I look forward to seeing more vids, and expecially out on the track!

Good Luck
Kenlude97

 

Thanks guys. I want it done and drivable too!

Regarding "take the intake tube off. start it and get it to bounce. stick you finger over the hole at the bottom of the tb, if there is vacuum/it stops jumping, it may be broke."

I though the FIAV was open when the coolant is cold, allowing air to go around the throttle plate thereby making it idle fast. If so, there should be vacuum on the hole when it's cold, right? Once it's warmed up, the coolant temp shuts the valve, and the vacuum should be gone. How is my thinking wrong.

Anyway I'll check it out, thanks.

 

I have had that issue before. Make sure that there are no vacuum leaks from the hoses and if you eliminate that then make sure that the IM and TB are bolted on well.

If you still have the Fast Idle Thermo Valve located under the TB if that goes bad it will let more air into the manifold than you want. You can also take that off since you live in california as it is never cold. I took mine off and have no problems below freezing.

I think you can also get a bouncy idle from the EGR not closing all the way. You can fix that with a small piece of aluminum under it to block it off. I doubt it will significantly affect emissions.

Hope it goes well, it's always an awesome project.
Pirate

 

200deg seems hotter than normal. Is the thermo valve itself hot? If it is not plumbed into the coolant system or if it is not getting hot for some reason, it will stay open and cause a fast idle which will conflict with the target idle the ecu is trying to get with the idle solenoid. To see if the thermo valve is leaking, you can do as suggested and plug it's port just in front of the throttle plate with your finger while the engine is idling. I think it's the lower port.

 

PirateMcFred,
I've checked for vacuum leaks... I'll look again. It's basically a stock engine, with only the EGR being removed and blocked off,so everything is tight, including the IM and TB. I assume if I take off the FITV I must block the passages. I'm all for removing stuff, for simplicity sake.

Flyrod,
No, the thermo valve is not hot so I suspect an air bubble. Either way, I do need to get rid of the air bubbles.

Thanks again guys.

 

Yes you have to block the passages on the FITV if you want to remove/disable it. You can follow the coolant lines back to the thermostat housing and just block them off there or you can fab a quick gasket to put between the TB and the FITV and keep it there for the sake of appearences only. Personally I would remove it all together. And while you are at it, remove the coolant lines going to the IAC too. Just my 2¢

Pirate

 

if I were you heres what I would check: Bleed FITV coolant lines/coolant system & use multimeter to check the TPS is working fine to spec.

 

The EGR can cause the bouncing idle syndrome.

This is generally when the EGR valve is sticking / has rough movement.

I was experiencing this problem after my swap.

If you are not using the EGR system, then you should cut out a metal cover plate and block the holes under the EGR valve.

Vacuum leaks can also cause increased idle speeds.

...as can an air bubble in the CAIV. (sp?) Keep in mind that it's the Control Air Idle Valve... not the COLD Air Idle Valve... So that valve is used to control the air mixture at idle. It can fail in a number of ways... if you haven't done this yet, try cleaning it with carb cleaner.

On the H22A4 for the 5th Gen, correct idle speed is 700 RPM +/- 50 RPM at 15 degrees BTDC +/- 2 degrees.

I've got to assume the 4th Gen P13 is similar.

The only time I've seen my 5th Gen idle at 550 RPM was when the injector timing was screwed up due to my inproperly installing an aftermarket distributor.

 

is yours a jdm or usdm h22, from my memory the jdm h22 does not have the cold start air valve, but if you have a usdm h22 it will have it, and this can also cause some problems.

First thing that came to my mind, was you had your egr removed, or do you have it just blocked off, the stock p13 with get very cranky when the egr is just strait out removed. i also doubt that the ELD being removed is causing your problem.

ok well here is a couple things you can do. with the intake pipe off, there are acouple ports exposed before the throttle plate. one if for the fast idle thermo valve, and the the other is for the IAC. once the car is warmed up you should not have any air being pulled into the port for the FITV. make sure you don't have any obvious vacume leaks, because the up/down is very clasic of a vacume leak as im sure you know.

the thing that you also mentioned that i thought odd was that once you unplug the iac your idle stablizes. i would take your iac off and get some carb / brake cleaner and clean all the crap out of the iac, they get so nasty. if the iac isn't all gummed up then sounds like air press is fluctiating in the manifold and the engine is trying to compensate with the iac to acheive proper idle rpm.

well i hope i was off alittle asistance, or atleast helped lead you in the dirrection of your problem. make sure you do post up the problem if you find it. certianly one dirrect route to go is , to block off the FITV and colt start air valve, to eliminate more variables.

edit: a 550 idle is very low, i think that is what the hels says, but the lowest i have seen it is 750 which is what your supposed to be at to set engine timing on the dizzy. but idle is completely warmed up with no electrical accessories on..... hmm.....electrical accessories, ELD can make the ecu increase or decrease idle. higher engine load requires greater idle speed............. just something to chew on, and a stab in the dark

 

Thanks for all the ideas. Since I've been spending all my time building the car I haven't become totally familiar with the ECU. I'll look into the following. (BTW, it's a USDM engine.)

1. Vacuum leak.
2. Air in the cooling system - likely since the system was just filled. Since I haven't run it to higher rpm, it's possible it won't self-purge until I do. Another hint is that the coolant lines to the two valves in question stay cold... not good.
3. IAC failure. I doubt it since unplugging it makes the engine run different, implying it is opening/closing the air bypass.

4. FITV. If hot coolant never reaches this, I can see how the high idle would be maintained forever.

Thanks for all the leads and I'll get to work on it.

 

Update:

It idles fine now - thanks for everyone's help. I removed both valves and bypassed the coolant. I still don't know what was going on... I suspect one was plugged up because while there was hot coolant in the line, it didn't appear to be circulating. There may have also been an issue with the MAP or TAP, but if there was it magically went away... we'll see.

Thanks again guys.

 

Glad to hear its coming on well, Can't wait to see a video of this thing once you've finished setting it all up props to you for having such dedication to such a cool and original project!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kb58 &raquo;</TD></TR><TR><TD CLASS="quote">Update:

It idles fine now - thanks for everyone's help. I removed both valves and bypassed the coolant. I still don't know what was going on... I suspect one was plugged up because while there was hot coolant in the line, it didn't appear to be circulating. There may have also been an issue with the MAP or TAP, but if there was it magically went away... we'll see.

Thanks again guys.</TD></TR></TABLE>


I read up on your site a little more... The reason you where getting the surging still was because you took the iacv off.. it will go away and come back. I had the same problem when i made a blockoff plate.

-Josh

 

Well I suppose that it's disappearance is good(?). Now if it never comes back that would be just fine

Pirate

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Blind Fashion &raquo;</TD></TR><TR><TD CLASS="quote">I read up on your site a little more... The reason you where getting the surging still was because you took the iacv off.. it will go away and come back. I had the same problem when i made a blockoff plate.

-Josh</TD></TR></TABLE>

That wouldn't surprise me, seeing how it just started working. I'll keep the IACV on the shelf just in case. There was a problem somewhere though...

Since the ECU no longer has any direct control over the idle I wonder what that remaining surge is from. I suspect it's the ECU fiddling with the A/F. Just wondering.

 

no pics of the car on your site or am I blind?

 

You have to go through the build diaries. It's in the final build up stage now so it's not complete yet. Here's a shot from about a year ago

http://www.kimini.com/Diaries/...2.JPG