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Old 08-22-2012, 07:26 PM   #1 (permalink)
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Video of "Cruise/Buck" & "Fickle Shift Light" (HF/Z1 Issues)

Hello everyone, I've been a lurker for some time & a sporadic poster at gassavers.org so I figure I need to spread my question around to a similar base to hopefully fix my problem & start enjoying my swap...4 years later. Here goes:

The long story is below:
'89 CRX HF + D15Z1 troubleshooting... - GasSavers.org - Helping You Save at the Pump Hypermiling and Fuel Efficiency Forum

The short story:
Issue 1: When decelerating in gear, the car cannot cruise smoothly. The vac gauge needle bounces/flutters slightly while the car "bucks/jerks" as if someone is lightly tapping the throttle & releasing in quick succession.
Issue 2: While accelerating (in 3rd gear mostly) the shift light flickers & acceleration smoothness suffers in direct relation.
Issue 3: In neutral, if I rev the engine, the revs do not come down gradually like every other car on the planet. The revs hang and slowly die off in an erratic (but always descending) manner. Imagine the engine falling down a flight of stairs, versus free falling.

Things to consider:

- I have NO CEL.
- I have thoroughly checked TPS & MAP sensors.
- I have cleaned the IACV port.
- I have ruled out the ECU & throttle body.
- If I reset the ECU by disconnecting the battery, she runs great for a few dozen miles before the symptoms resume.

Issue 1:


Issue 2:


Next up is vacuum testing the entire EGR/VX Control box system, including hoses.

Any help is appreciated, thanks,
Mak

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Old 09-05-2012, 03:16 AM   #2 (permalink)
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Update:

Replaced most vacuum hoses as some appeared OEM. I tested both the EGR and control box devices per HELMS to no avail, they seem to be doing their job fine & I cleaned the main thermostat ground just to be safe. It must be noted that if I unplug the TPS & drive every problem goes away, minus the code & very high idle. If I knew my MPG wouldn't suffer I'd unplug it & never look back, THAT'S how annoying & persistent this problem has been. Any ideas? I may remove the intake manifold and deep clean the EGR ports but I'd rather have a focus & not just randomly try/buy solutions that don't work & piss me off in the process. Thanks, Mak
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Old 09-05-2012, 10:06 AM   #3 (permalink)
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I read your posts at Gassavers.org
I would wager the EGR is loose at the gasket after numerous attempts to remove it have failed.
There are 2 holes that the EGR covers and regulates and the gasket seals between them , if there is a leak either between the 2 holes or outside of the gasket it will give you a horrible random bucking.
I would do what ever it takes to get the EGR removed and minimum use high heat RTV to reseal the gasket.
My VX has never had the bucking issue but I had a '79 Ford Fairmont 302 that had the exact same issue, solved the way I described.
Hope it helps.
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Old 09-11-2012, 03:44 AM   #4 (permalink)
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Thanks for the info WD40, if you truly read my entire post at gassavers.org you are a trooper, it goes for years & 100+ posts. Anyway, I have done everything imaginable to the EGR bolts to no avail, despite a heavy dose of PB blaster. I'd tried flare nut wrenches, locking pliers, etc. Once they rounded off something horrible I hammered a size smaller on each = fail. I even tried the chisel + hammer technique and finally a gator grip adjustable socket = fail. At this point my choices are drill it out or take off the entire intake manifold to gain better access around the fuel line/rail with monster locking pliers. I won't be able to remove the manifold until Project Darkness is complete, give a me a month or so & I may have an update.

Thanks,
Mak
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Old 09-11-2012, 09:23 AM   #5 (permalink)
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Have you tried using heat on the bolts? Cut a slot in the top of the bolt Then try using a torch to heat the bolt up. The bolts get heated/cycled every time the engine warms up cools down. Heat could expand it enough to break it loose.
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Old 09-11-2012, 10:16 AM   #6 (permalink)
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The bottom line is that the nuts need to come off.
I have had to use a chisel to split a nut that was stuck before.
You only need to split one side as it will spread easy once its split.
It does work really easy and the end result is you get the nut off.
You just need to try and stay away from the bolt itself, nuts are easily replaced.
The nuts are usually softer material then the bolts.
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Old 06-13-2013, 03:08 AM   #7 (permalink)
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Months & months later, some old crap I parked her for different periods to test my '97 Hatch+HX project but the in gear jerks remain among the rest of the symptoms. I've resorted to pulling the IACV plug & letting the CEL shine bright because other than a low idle & jerking in low RPM, low gear situations, she's fine. I may eventually hook up a 10watt, 10 ohm resistor to trick the ECU into turning off the CEL but for now she still hits VTEC & I imagine lean burn (won't know til a burn a tank & compare past numbers). BTW, blocking the IACV off completely but leaving it plugged in simply lowered idle & worsened my decel jerks. Go figure. Unplugging just the TPs had similar positive results except for an unacceptably high idle + CEL,

Mak
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Old 07-13-2015, 06:02 PM   #8 (permalink)
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Ha, some things never die. Every year or two I get a notion that my issue is simple & if I just take another look the solution will be found. Fail. Maybe this time will be different.

Current setup: unplug the stock IACV (leave it bolted to manifold) & plug it's harness into a dummy IACV that isn't physically attached to anything. Simply unplug the TPS to prevent a high idle. Completely eliminates the cruising/jerk condition but it has trade offs. The idle upon cranking is rather low (no big deal) but the alt. volt reading is pegged at 14.4v, I assume the TPS CEL disables the ELD. I put everything else back stock & the jerk returns with a vengeance, but the volts fluctuate like they are supposed to. The fact that I can't figure out the problem is almost as infuriating as the side effects themselves. Any thoughts?

I've thought of slowly testing each component one at a time by making sub harnesses directly wired to the ECU in case the signal is getting molested along the way somehow. This IS an ODB-0 car with OBD-1 jump harness after all, and it has never behaved stock.
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Old 07-13-2015, 06:11 PM   #9 (permalink)
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Thunder - '85 Honda CRX Si
90 day: 44.84 mpg (US)

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90 day: 41.84 mpg (US)
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The original link in the first post is bad. Below is the correct one.

'89 CRX HF + D15Z1 troubleshooting... - Fuelly Forums
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Old 07-15-2020, 11:57 PM   #10 (permalink)
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Thunder - '85 Honda CRX Si
90 day: 44.84 mpg (US)

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90 day: 45.43 mpg (US)

The Darkness - '97 Honda Civic DX
90 day: 41.84 mpg (US)
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TL: DR - the cause of this 15 year headache has been a faulty sensor ground (D22) that tested fine but would intermittently short while the car was running.

Back from the dead! Hard to believe but I've been dealing with this problem for over 15 years but I believe the solution has been found. I've been living with this nagging issue the entire time and only after a pet peeve quota was reached would I hunker down and try to figure out the cause, fail, then go another few years and repeat the process using some other theory. Anyway, long story short it was a ground wire (D22) that provides logic ground to the throttle position sensor, the O2, the EGR etc. The conversion harness supplied by Rywire back in 05 had a single purple ground wire that was to be tapped into for all those sensors. Only after inspecting every single wire by hand did I reach the culprit. Where the ground wire goes through the firewall the insulation had been worn just enough to provide contact thus grounding the circuit improperly. Back in 08 (and 10, 12, 16) I had checked the TPS with the engine off and key on and the numbers came back good! What caused the issue did not present itself until the vibration of a running engine caused the wire to tap randomly into exposed metal which is why it was so hard to nail down. A new ground with solder, shrink wrap, and Super 33 tape solved the problem. I replaced any connections that looked suspect while I was there but only D22 had obvious damage. It's only been a week but I cannot remember a time the car has idled smoother, decelerated as linear or general driveability has been as pleasant. Still not new car smooth, but a Caddy by comparison to the way it was.

PS. the method I used to find the problem was to disconnect one sensor at a time until the symptom went away. After 15 years and multiple attempts to diagnose the problem the flowchart/helms way did not work in this case, it was too random vs a simple dead sensor. Unplugging the TPS left me with a high idle but smooth as glass decel with an obvious CEL for TPS but also O2. Going back to the wiring diagrams I saw that both sensors shared the D22 for logic ground and thus my discovery. I knew it wasn't the O2 bc she would act up on cold starts before the O2 even came onboard closed loop. Wasn't a vac leak because it was never consistent (and I'd regasketed the entire intake side over the years). To summarize, I hate wiring and it is occasionally the work of Satan.

Mak

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