'89 CRX HF + D15Z1 troubleshooting...

[MakDiesel]

I'll doublecheck the wiring soon, a used TB is on the way just for a quick rule out of the current one. I have checked the current TPS w/ a MM per HELMS and found it to be within specs, no unusual jumps w/ opening/closing but I didn't have a graph w/ my MM, I only saw a steady progression on the Volt readout. I'll also be replacing the TB gasket and IACV o-rings while I'm there for safe measure. Thanks, Mak

[MakDiesel]

checked the TPS wiring today w/ a MM, all connections have continuity to their respective ECU ports, although for my setup and the ECU reference sheet I've been using, D20 is the TPS reference voltage, D19 is ref. volt. for the MAP. Is this the same for you guys? Mak

[MakDiesel]

Well, disappointing news. I swapped the TB for a known good one and the problem did not go away The idle is lower, granted, to about 1.1k when it finally levels out but it still "hunts" up and down when in neutral and still bucks in gear while cruising. Ugh. Tested the volts of the MAP (w/o vac til I get a vac pump) and the white wire I believe is getting 3.6 volts, but some references I have say 3v (depending on temp.) and others 5v. Also, while idling in the driveway w/o any lights, she hums happy at 1.1k. I flip the parking lights on, she hunts between 1.1k and 1.3k. I turn on the fogs and she hints higher, say 1.3-1.5k. Any reason for this? I may have not noticed it before today or it's a result of the new TB. I'm guessing alternator volt. reg. or EL (electric load) device. Any insight would be helpful. Mak

[GasSavers_bobski]

It still sounds like a vacuum leak or IACV issue. Try pinching off the vacuum hoses again. Towards the beginning of the thread, you said the PCV valve hose made the idle speed drop... By how much?

[mrmad]

Not to jack your thread, but I've been having some similar idling issues on my CRX HF and thought my issues might shed some light on your issues and may be answer a few questions of my own.

First, my HF used to idle perfectly at ~750 rpm. Then it started intermittently getting around 1000-1100 and would intermittently bounce from 1000-1500. It would sometimes calm down back to 750 by blipping the throttle. I could try to set the idle air screw and it wouldn't seem to stay at what ever speed I set it at. I cleaned the IACV, throttle body, and sprayed carb cleaner through the idle air screw port to clean it out and reset the timing. I also checked to see if the TPS was functioning by measuring the voltage from it and it seemed to be fine. After cleaning out the throttle body I think I have gotten rid of the bouncy idle (though I've only driven it a few times and it could come back).

I did notice what you did with your throttle body when holding it up to light, when closed, there still is a small amount of a leak through it. Right now, I have the idle air screw all the way closed and it is idling ~800. Before I cleaned all the gunk from inside the throttle body, I think the gunk was clogging this small gap because it wouldn't run with the idle air screw all the way closed. I tried moving the set screw that is the stop for the throttle but even with it turned all the way out, the throttle plate would always have a tiny gap between it and the throttle body. I don't think this is the way it is supposed to be, I think the throttle butterfly should close all the way and the idle speed should be from the idle air screw. Now when I blip the throttle, it will idle at about 1000 rpm for a second or so and then settle down to about 750. Occasionally, it will drop down to about 500rpm and a blip of the throttle will bring it back up. I probably wouldn't care about this as long as it idles relatively OK, but I have to get the car to pass CA smog this month and am not sure it is stable enough to pass. I think my throttle body is worn where the throttle butterfly contacts it and it is leaking air through the gap. I imagine the butterfly isn't always closing at the exact same place each time the throttle moves. By the time the set screw on the throttle stop makes contact with the throttle, the gap is even bigger, so right now the main thing that is controlling the stop is where it ends up.

Sorry to write such a novel on the subject, but does anyone know if a new throttle butterfly closes all the way, or is there supposed to be a small gap between the butterfly and throttle body?

As far as the misfiring you are having, I didn't see if you've checked to see if it could be from old/worn distributer cap/rotor and or spark plug wires?

[GasSavers_bobski]

Originally Posted by mrmad

Sorry to write such a novel on the subject, but does anyone know if a new throttle butterfly closes all the way, or is there supposed to be a small gap between the butterfly and throttle body?

There should be a tiny gap there to deal with thermal expansion. If you look at the sides of the plate (where the throttle shaft meets the throttle body wall) you should see a similar gap. If the throttle stop screw is adjusted properly, the plate should never contact the wall, and as such there should never be any wear between the two.
When you adjust the idle speed, have you been disconnecting the EACV/IACV as the service manual says?

[mrmad]

Originally Posted by bobski

When you adjust the idle speed, have you been disconnecting the EACV/IACV as the service manual says?

I tried that today which meant having the idle air screw open about a turn. Once the EACV was plugged back in it started the idle surging with a vengance. With the EACV unplugged it would idle smoothly. I have a spare ECU I got on EBAY and tried it and it changed everything. Now the car idles perfect. I wouldn't have thought it would have been my ECU, but at this point I'm not going to complain.

[suspendedhatch]

Well did you reset the ECU after you adjusted the idle?! Put the old ECU back in and see how it idles.

$15 repair manual can save you lots of money and headaches. On an OBD1 Honda you let the engine warm up, jumper the diagnostic plug, disconnect the IACV harness, adjust the throttle body screw to the spec in the manual (usually 600 RPM), stop the engine, remove the jumper, and reset the ECU by pulling the 7.5A backup fuse under the hood. Drive it around the block and check it with a diagnostic tach to make sure it's idling within spec (usually 700+/-50).

If you adjust the throttle screw w/out jumpering the ECU and w/out resetting it afterward, the ECU continues to use it's "learned" settings resulting in an overly high idle. The reason it revs up and down is because the IACV is open too far in combination with the throttle screw which raises the RPM up until you hit the DFCO point which cuts fuel and makes it drop back down.

[mrmad]

Originally Posted by suspendedhatch

Well did you reset the ECU after you adjusted the idle?! Put the old ECU back in and see how it idles.

$15 repair manual can save you lots of money and headaches. On an OBD1 Honda you let the engine warm up, jumper the diagnostic plug, disconnect the IACV harness, adjust the throttle body screw to the spec in the manual (usually 600 RPM), stop the engine, remove the jumper, and reset the ECU by pulling the 7.5A backup fuse under the hood. Drive it around the block and check it with a diagnostic tach to make sure it's idling within spec (usually 700+/-50).

If you adjust the throttle screw w/out jumpering the ECU and w/out resetting it afterward, the ECU continues to use it's "learned" settings resulting in an overly high idle. The reason it revs up and down is because the IACV is open too far in combination with the throttle screw which raises the RPM up until you hit the DFCO point which cuts fuel and makes it drop back down.

Yes I reset the ECU and that's when it started idling worse until I swapped to my other ECU. And yes I have a manual.

[suspendedhatch]

Originally Posted by mrmad

Yes I reset the ECU and that's when it started idling worse until I swapped to my other ECU. And yes I have a manual.

Cool. Glad you figured it out then. That's pretty unusual but I guess it happens.