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

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

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

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?

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?

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?

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.

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.

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

I've got plenty to check on my Z1, mainly each and every vac line, but I'll reset the idle per HELMS spec to rule that out. I had just figured that neither my TB's had been tampered w/ and were not out of factory spec. I'll make a list of every attempt I've made at locating the problem if this doesn't work to cut down on having to read the entire thread over for those w/ advice. Thanks, Mak

For the uninitiated: '89 CRX HF w/ D15Z1 swap (approx. 100k on motor), HF cable tranny, no A/C, stock airbox/stock exhaust dumps at pass. wheel/no muffler, 5-wire O2, P07 ECU

Problem: Cranks fine, warms up fine, idles like crap under certain conditions, bucks under in gear, no throttle deceleration. Here's the interesting part; today I warmed it up, it idles at 1.1k smooth. High, but smooth. I put on the parking lights, instantly has looping idle, 1.1k-1.3k, kinda fast. I turn it to lights, the idle loops higher and longer, say 1.4k-1.8k. I turn all lights off, she settles back down to 1.1k and holds steady. I hit the brake lights only, she goes back to when the headlights were on in loopiness factor. I let off the pedal, no lights, back to a steady 1.1k. Tried to set idle lower but it's already low enough when the IACV is unplugged. What gives?

Here's what I have so far...

1. cleaned IACV
2. Swapped/cleaned TB for known good one, cable adjusted
3. Liberally sprayed Carb cleaner multiple times on hoses, gaskets, no found leaks
4. Spark plugs correct and not worn
5. new plug wires
6. Dist. cap in good condition, no carbon build up
7. new fuel filter
8. mechanical and electrical timing spot on (when idle not fluctuating)

9. TPS voltages, engine off, ignition on; (Range is .5 - 4.5v, no spikes)
if yel/wht = a, red/blu = b, gr/wht = c, then:
a = 5v (red probe in "a", neg. on chassis ground, etc)
b = 0v
c = 0v
a(pos) + b(neg) = 3.5v
a + c = 5v

10. MAP voltages, engine off, ignition on:
if yel/wht = a, grn = b, red = c, then:
a = 3.6v
b = 0v
c = 5v
a + b = 3.6v
a + c = 0v
b + c =5v

11. EGR voltages, engine off, ignition on:
if yel = a, wht = b, grn = c, then:
a = 5v
b = 0v
c = 0v
a + b = 4v
a + c = 5v
b + c = 0v

12. Fuel injectors can be heard w/ a screwdriver ticking at idle, then shutting off when coming down from a high RPM.
13. P07 ECU swapped for a known good one, no change.
14. Tried to set idle according to HELMS, but she fluctuates lightly at an indicated 650-800 RPM, sometimes cuts off if I bring her down too fast.
15. New timing belt, water pump.
16. Temp. sensor has 5v, Ohms seem to be in spec (I forget the actual Ohms)
17. New 87 octane (just making sure)
18. Valves recently adjusted
19. The worst part, no CEL unless I unplug something! I reset the ECU after each provoked CEL though.
20. Unplugged the TPS for kicks one day, acceleration seemed better, no loopiness, idle was very high, doubt she bucked in gear w/ that much idle, and CEL of course.
21. Next up is fuel pressure, poss. new O2 (nooooo!), and a alternator/battery check from Autozone cuz it's free.

Any insight is appreciated, this issue is a nagging one... AD

When you unplug the IACV, the engine idles at _____.

Though it may not be your problem - looks like you've tried most everything else - have you tried cleaning the engine grounds?

I don't have a handheld tach, but the indicated RPM was lightly looping from 700-800. Also, some of my grounds were replaced/upgraded during the swap, including 4 gauge ones going straight from the neg. battery cable to the distributor, TB, and fuel rail to supplement 4 gauge neg to chassis and valve cover to chassis ground. Are there any others that need to be checked? I remember the one mounted to the thermostat housing is important....anyway, video of all of these issues is coming, hopefully in a few days.....AD

a flathead is all you need to solve the world...
 

Here are two videos, first is the various rev loops after the car is warm, noting the different patterns w/ brake lights, parking lights, headlights, vs. all off, etc.
Rev loop patterns

Video two is simply idle w/ IACV unplugged
IACV Unplugged

After I shot these I lowered the idle to an indicated 450 RPM, then hooked it all back up, erased CEL, then fired her up for a 3 mile test drive (it's too cold to be doing this in an open air shed = fingertips hurt from the cold). Anyway, 90% of the problems are gone as far as I can tell. The bucking has completely stopped as far as I can perceive, the idle is a low 650 +- 50, and the looping is still faintly there, but greatly diminished to about 15% of what it used to be, and it levels out much faster. It's more like the idle is 650, I kick on an accessory (say headlights) she idles up to 900, then falls back down, or depending, also falls a bit before returning. Not bad. And definitely something I can deal with on a daily basis. Sweet. I'll continue refining the drivability til she's as smooth as my '85 CRX Si w/ 238k, which is butter. Thanks everyone for their insight, I'll keep you posted once I get more time on the road, Mak

By any chance would you happen to have a picture of your vacuum lines from your egr, tps, etc. I did the same swap but some of the vacuum lines and maybe the 5 wire 02 aren't hooked up right.

well, I'm pretty bummed. After a brief problem-free run, she started acting up again. The bucking is back in full force, the idle doesn't loop anymore but it still doesn't settle low enough w/ the lights on, and on an unrelated note after a casual run she blew all of her coolant out via the overflow tank, boiling and steaming out. After a refill and tightening she is fine but the persistent cruise-buck is really irritating. I will be checking each and every vac line, then re-do some wiring, then O2 sensor, then I'm chucking her off a cliff, aflame. Mak

max - Ill try and find the diagram I used to hook all mine up.

That's not a good sign, you know. Replace the radiator cap... If you still get bubbles out the overflow, you could have a bad head gasket.

I've driven it 8 times since w/ no problems, dunno why the problems this car has are so intermittent. She's kept all her coolant since that drive. I did notice the cruise/buck is also hit or miss, sometimes not appearing until after I'm almost home, 3 miles down the road. It seems to be a closed loop only problem. Does this rule out vacuum, fuel pressure, and electrical issues? My guess is inching closer to the O2 (or other sensors, chime in please), as the symptoms only start acting up once the car reaches operating temp, or at least beyond "C". The test drive continues...40 miles and counting...Mak

110 miles and counting, no 'new' problems, just the persistent one. Quick Q, what would cause the upshift green arrow to spas out sometimes and flicker when accelerating kinda slow before deciding to say "yes, please shift" w/ a solid green light? Vac issues? Checked the EGR diaphragm, it moves easily enough, next up, full wiring reverse engineering (make sure what goes where is correct, as the old EGR 3-pin still has a current...hmmm) Mak

It's entirely up to the ECU to decide when to light the upshift indicator. There is a circuit board on the back of the gauge cluster that does the grunt work of actually applying power to the bulb and dimming it when the headlights are on, but it's a dumb circuit - it just responds to on/off signals from the ECU and parking lights.
If the light is behaving erratically, I would check the wiring between the ECU and gauge cluster connectors, and the connections on the back of the gauge cluster it self. If everything checks out in that respect, I would check the power supply and ground to the gauge cluster and ECU, then the possibility of a bad ECU.

I would really like a V tech light in mine, what wire is safe to tap a LED into?

What... like this?

Um, no :o

more news of the weird...The car recently started having a pronounced misfire when cold followed by rough running, light looping, warm idle so I hit the wiring harness for answers (Still no acceleration or light pedal cruise problems btw). After transcribing all of the OBD-0 wires under the dash that connect into my rywire harness and isolating the main sensor ones (TPS, MAP, EGR, O2, etc), I'm suspicious of my EGR wires when compared to HELMS. The power is still 5v, but the middle wire (can't remember color off hand) isn't the factory 1.2v w/ no vacuum, it's 0v w/ key power (Run) but no engine start....anyway, after simply handling the bundle, ECU, etc I start the car and virtually all my previous problems don't exist! No misfire at cold idle, no rough warm idle, no buck/jerk, not much rev hang in neutral... go figure... so I may have a short somewhere or a fickle EGR/sensor issue...260 miles in, she rides smooth, for now...Mak

Get the honda service manual, the helms manuals are absolutely useless. You can download the honda service manual online and will be far more detailed than the crap helms manuals you and I can get for $20.

The Helm's manual IS the Honda service manual, smart guy.

I guess I confused it with the like of a chilton manual. As for the helms, I just call that the OEM service manual, but I guess Helm's is easier to say. Btw I thought I should mention that the idea to put a roll cage in your civic is a very BAD idea unless you plan on driving around with a helmet b/c that cage will cave in your skull w/o a helmet, even with padding on the cage.

Chilton and Haynes write their own service manuals... Helm, Inc. reprints factory service manuals.

Who said anything about a roll cage?

Sorry that post was directed towards the OP, I just thought you were the OP and figured I'd throw that in as well. Yes when you said Helm, I was thinking of Haynes and the like.

Re: '89 CRX HF + D15Z1 troubleshooting...
 

Hey buddy, did you ever end up resolving that bucking issue on your crx ? Im in Australia and I have the exact same problem ! Cant figure it out !!

Re: '89 CRX HF + D15Z1 troubleshooting...
 

Sadly, I never really figured out the cause. I continue to drive the car on weekends and for fun, maybe 4-5k miles a year and the buck issue comes and goes, right now it's in full force. Definitely irritating, but other priorities are taking up time. The Shift light still flickers before staying lit and the bucking seems to get worse after I've hammered her a little. Eh, I'm out of ideas but my guess is wiring or vacuum related. It's the only thing keeping this car from being 100% success tho. Mak

P.S. on the upside, MPG has been a consistent 55-60 this year!

Re: '89 CRX HF + D15Z1 troubleshooting...
 

Overdue update time...

I had a spare minute today and decided to play around with this everlasting buck problem that has persisted so long. I warmed the car up and drove her back to back with the TPS hooked up like normal and then without (with CEL glaring) and it was like night and day! With the TPS hooked up she's a temperamental beast, lower idler, studders mid-shift, and bucks randomly in gear w/ no throttle input. W/o the TPS hooked up, she rides like a caddy, accelerates without fuss, and DOES NOT flinch when decelerating in gear! If it wasn't for the high idle (1.6k-ish) I would just leave her unhooked and say f-it. Anyone want to chime in on how I can make this problem go away (with no CEL & high idle)? Thanks, Mak

P.S. The ECU has been checked w/ a known good one, the TPS (with sensor) has been checked before, and the wiring reports correct respective voltages as reported literally years ago in this thread.

Re: '89 CRX HF + D15Z1 troubleshooting...
 

bad wiring bad/intermittent failure of TPS sensor?

Re: '89 CRX HF + D15Z1 troubleshooting...
 

Perhaps in the wiring between the sensor and ECU.

Re: '89 CRX HF + D15Z1 troubleshooting...
 

I'm more than frustrated on this problem, as it has plagued me since day one of the successful swap. My next free day I'll rewire the sensor directly to the ECU pin-outs and then I should have my answer...or more difficult questions...hopefully it was a simple switch of the wires, a worn piece of wire grounding out, or possibly a Rywire fault on the conversion harness, altho that's remote.

Thanks, Mak

Re: '89 CRX HF + D15Z1 troubleshooting...
 

Spent several hours Friday tracking wires and voltages, long story short the TPS cannot be my problem, nor can the MAP or conversion harness. Considering that when I disconnect the TPS, the ECU artificially raises the idle to compensate & all my problems miraculously disappear, I'm going to reset the idle according to HELMS and go after the IACV and that other manifold sensor (TW in the book IIRC). After that, it's on to the O2 sensor and I do not want that to be a costly lesson in bought-but-didn't-fix lesson. Mak

Re: '89 CRX HF + D15Z1 troubleshooting...
 

if you do go ahead with cleaning the IACV, I suggest taking off the throttle body and giving it a thorough cleaning. I know on my throttle body there was a lot of gunk inside of the passages, especially in the passage for the the idle screw. Btw, have you replaced the PCV valve? Checked for vacuum leaks, etc?

Re: '89 CRX HF + D15Z1 troubleshooting...
 

When I swapped TB's I cleaned the newer one before installing, no change. I've cleaned the IACV recently, the mesh looked fine, now I'm leaning towards electrical issues with both sensors, something I haven't tested. The PCV valve is new, and with the straight-through VX design I don't see how it can fail, it's just a hollow elbow. I've sprayed at least a solid can of Carb Cleaner on every hose/intake manifold before trying to find vac leaks, but have never witnessed changes in idle. Has anyone ever deleted the IACV to get a more predictable idle, and erase common Honda surge issues or is this just more trouble than it's worth?

Mak