After about a year of getting a major performace upgrade for my engine, I have been having an idle problem.

At first the engine would turn over with ease (like when you turn the key and it fires right away) but stumble while idling (RPM would drop to about 500 and serge back up and then idle normal).

This has going on for about 3yrs now. But just recently it's gotten worse where it takes a few seconds for it to turn over and now when I come to a stop the RPMs just drop to like 200 and slowly rise back to normal and sometimes it will stall. But if I slowly come to a stop, the RPMs will still drop but it won't stall. I've also noticed that when this occurs that my fuel prseeure drops too.

Now mind you this behaviour does not always happen. Sometimes the idle is rock solid when I come to a stop but the cranking is still the same.

I have read on a lot of other boards that the culprit could be the IAC/EACV valve or the FITV. So I decided to check that out.

From my Honda service manual it says that with the engine warm to plug the IAC valve (located in the TB) with your finger and if the idle drops then to replace it. So I did just that but nothing happened (hole #1).

I then went on to plug hole #2 with my finger and the engine "died". From what the diagram in the manual looks like, hole #1 should be the IAC valve but the picture of the IAC valve looks more like device #4 which I think is connected to hole #2. Is this correct?

I'm also thinking that it could be the PCV valve and I have yet to change that.

Can someone please list what the indicated #'s are and what I need to do in order to clean the screen for the IAC valve? And shed some light into what my problem can be?

Here's some more pictures.

 

#3 is the TPS I believe.

I had the same wandering idle.

I adjusted the The TPS, it can be adjusted back and forth just like the distributor.

Play with that a little and see if that helps.

 

yep..#3 is definitely TPS..

the drop in fuel pressure could be attributed to the drop in idle..
when you're lagging down to 200 rpm your alternator isn't pushing the same amperage and satisfying what your car is requiring, including your fuel pump, so everything starts to drop off..

let's say your FP needs 30 amp..
alternator is throwing 10..
what happens?? fp drops off, so does fuel pressure..

when's the last time you sent a can of tb cleaner down that throat??

 

I agree that it's the lower one... #4 Odds are though, all this speak of IAC has got you not thinking straight. It's very doubtful that the IAC amazingly and suddenly after the major upgrade started to malfunction.

what I'd like to know, is EXACTLY what fuel solution do you have (engine management?) cuz a great majority have just that - idle problems. Big injectors, slightly off fueling = stumbling. Your newly developed or worsening problem is likely a result of the ignition unable to light off an overly rich condition at idle cuz of component wear. See, the stock ECU is unable to recognize injectors bigger than 320ccs, so it fires a 440 injector as if it were a 320, creating your idle problem. Do you smell gas from the exhaust at idle?

 

Check your valve lash I had the same problem and the valves were tight.

 

Have yet to do that

Fuel manangement is handled by an FPR, FMU, and high flow fuel pump. Everything else is stock.

But how can this happen after about a year of working fine?
Won't lowering the fuel pressure help in the overly rich idle?
Yes I smell gas @ idle.

 

Well, after a year of working fine, maybe the spark started to slowly get weaker and it's now having trouble lighting the rich mixture.

If you smell gas at idle (even when the engine is warmed up???) then your tuning is off. It's not a sensor fault... more of a tuning problem very likely. That's one of the main problems with hacks... you end up sacrificing driveability a lot of the time. Think... what's changed from when you started having the problem? If you have a OBD2 scanner, get with your laptop and start checking out your running parameters. Check TPS, ECT, IAT, and O2 readings. It will give you fuel trim, idle speed (desired and actual)... pretty much every sensor readout you could want to look at. If it all checks out as being correct, it's time to get with a dyno fascility and start tuning.

 

But why would it happen randomly? Sometimes it's ok and other times not?

 

your FMU... what inputs does it use?

 

Vac comes from manifold and fuel inlet comes from FPR (AEM) outlet.

 

Do you have a vacuum reserve canister? Is your vacuum/boost gauge steady?? 12:1 disk, right?

Perhaps consider an S-AFC upgrade for easier tuneability. This is really tough to make a call. The problem is resolvable, but it'll take a commitment on your part to test, and test again until you track down the culprit. The throttle-body cleaner won't hurt, it's worth doing, but I think there may be more at work here than just some carbon buildup.

 

What's a vacuum reserve canister?
Gauge is steady at idle.
no disk. The FMU is adjustable. Dunno what it's at right now.

Well I do have a piggy back and which will control larger injectors (RC440) but I may wait until next seaon to put that in. But if this keeps on happening, I might just do it now.

 

did you get an SMC Plus? Well, vacuum reserve is as the name implies like a little tank for vacuum gets stored up in... but now that I think about it, that shouldn't affect the performance of the FMU.

 

Wow, surprised you knew about that device

 

bb knows all

 

I was just thinking that since I'm using the middle sized orifice in the AEM FPR exit port there's more fuel exiting the FPR into the Cartech FMU. Since that's the case wouldn't it be logical to reduce my fuel pressure/static pressure in the FMU to compensate for that?

 

Well, volume = diameter AND pressure, so if you want to maintain the same volume with increased diameter, then pressure must be reduced. So, you would be correct in assuming that's a good place to start.

Yes, I'm familiar with the SMC product... it's a very handy-dandy device, but a little impercise for my needs I'm looking to push the envelope on a stock block w/o losing driveability, so I need more percise metering control (w/o spending $1800 on Hondata).

 

Ok I tried adjusting my static pressures and it doesn't seem to be working.

The FMU won't go below 42psi and the AEM FPR is acting kinda weird. My static is equalling my fuel pressure (i.e. vac hose off and plugged 36psi. vac hose connected to FPR 36psi)

 

hmmm.... who tuned this for you in the first place many years ago? what is your FPR supposed to be set at? Normally it should be 42 psi prime, 36 psi running at idle.

 

It hasn't really been "tuned". Just set to specs called out from the instructions when I first got it installed. Then after a year it started happening and then I started swapping parts out as my knowledge grew on how to make this "thing" run/work" right. But this idle problem has not gone away and has just gotten worse when I just switched to an AEM FPR.