'89 CRX HF + D15Z1 troubleshooting...

[MakDiesel]

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

[MakDiesel]

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

[GasSavers_bobski]

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

[mrmad]

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

[MakDiesel]

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

[MakDiesel]

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

[GasSavers_maxpowers]

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.

[MakDiesel]

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.

[GasSavers_bobski]

Originally Posted by MakDiesel

on an unrelated note after a casual run she blew all of her coolant out via the overflow tank, boiling and steaming out.

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.

[MakDiesel]

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