fragmare

I've been trying to wrangle a few various annoying idle problems for a couple of months now. Here is what the car has been doing:

1. Idle will surge extra high at initial startup.
2. Will occasionally fluctuate up and down until engine is somewhat warm.
3. Car will drop RPMs when shifting into gear, under electrical load, or when A/C is on.
4. After running idle adjusting procedure in service manual, idle RPMs will only be at around 550-600 RPM while engine is warm (engine should be idling at around 700 RPM).
5. In order to force the car to idle at 700 RPM, I had set base idle RPM to about 550 when IACV power is disconnected. Base idle should be around 420 with IACV power disconnected.

Here are things I have checked and/or tried in order to remedy the problem.

1. Double and triple checked the mechanical timing. It's absolutely 100% dead on.
2. Set ignition timing (since I did replace the dizzy recently). It's dead on at 700 RPM.
3. Bled coolant for a good 30 minutes with front of car jacked up. Squeezed hoses.
4. Poked around the vacuum hoses and connections several times with carb cleaner and/or starting fluid for vacuum leaks. None were found.
5. Removed IACV and thoroughly cleaned it. Resealed the seal around the IACV electrical connector with Hondabond (it was visibly cracked and leaked).
6. Removed and thoroughly cleaned throttle body. Replaced TB gasket.
7. Removed, disassembled and thoroughly cleaned the FITV. Replaced one cracked o-ring.
8. Tested ECU with multimeter for A/T Shift Signal, A/C Signal and Alternator Signal. I don't have the test harness, but when probing the connectors, all seemed to fall within spec.

My question is, is there anything left to troubleshoot? Should I start shopping around for IACV prices, or is there something I haven't tried yet? I am all ears if somebody can think of anything.

fragmare

Bump. Any input?

Former User

When the idle is surging and the engine fully warmed up, remove the air intake system to expose the throttle body (TB). Inside the TB, there is a hole/port leading to the IACV or FITV. Cover each hole with your finger one at a time. Does covering one of these holes eliminate the surging and drop the idle speed? Do you feel any air being pulled through the FITV port?

fragmare

The idle only surges and fluctuates on cold startup. I'll try that, though, next time it acts up, and post my results here.

fragmare

Okay, shortly after a cold start, I caught the idle fluctuating from maybe 1000-1500. This was maybe 1 or 2 minutes after startup, before the engine was at full operating temperature. Blocking either inlet hole decreased RPMs and there was plenty of suction on both. I could not get around to the front of the car in time to see if blocking one of the holes stopped the fluctuation, unfortunately. The idle will only jump up/down maybe 4-10 times before it settles down, so I'll either need to be quicker next time or get my shop assistant (aka my gf) to help out.

Anyway, I went ahead and let the car warm to full operating temperature. Then I blocked the FITV inlet and felt no suction and there was no drop in RPMs. I'm guessing that means the FITV is doing its job and closing after full engine warmup. When I blocked the IACV inlet, the engine died, so I guess that means I don't have any serious vacuum leaks anywhere that I missed.

fragmare

I finally caught it in time. And, yea, putting my finger over the IACV hole drops the idle and stops the fluctuation.

One thing I have not tried yet is taking the FITV back off and tightening the inner white cap all the way down. When I reassembled the FITV after cleaning it, I simply set it back to where it was before I took it apart. I might try that later tonight, though I doubt it will fix all my idle problems.