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Let's diagnose a Honda! My buddy's car is misfiring 100% on #4. Important Details: - EG 1992 Civic with Mini-me swap completed 90 days ago and working fine - Traced misfire to cyl #4 by pulling plug wires - Removed plug and grounded against body and discovered very weak and erratic spark - Spark plug looks good - Disty rotor and button are new and in good shape. Sanded electrodes and no change was observed - Fuel smell in exhaust seems to indicate injector is fine - Revs ok, other than the misfire Not sure where to go from here, thoughts?
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Feb 6, 2015 21:35
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| # ? May 5, 2024 21:59 |
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Swap the HT lead over with a different cylinder (swap it at the dizzy end, too, duh!) and see if it follows.
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Feb 6, 2015 21:42
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revmoo posted:Let's diagnose a Honda! My buddy's car is misfiring 100% on #4. Important Details: Try here first Swap the plug and see if it follows. Did you check the gap? what about wires? those new? swap from 3 and see if it follows... etc.
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Feb 6, 2015 21:42
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revmoo posted:Let's diagnose a Honda! My buddy's car is misfiring 100% on #4. Important Details: Your best bet is to find a known good ECU and distributor if you checked the plug wires. Also double check the ECU ground on the thermostat. Do you know if it is an OEM distributor? The Ebay ones usually last about 6 months to a year. Are there any codes being thrown? (how to pull them) edit: You also will want to swap the #4 injector with one of the others to see if the misfire follows, it could be stuck open causing the misfire. doogle fucked around with this message at 22:52 on Feb 6, 2015 |
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Feb 6, 2015 22:43
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Tried swapping plugs and wires, no change. Dizzy is OEM. I'm a little scared to pull the fuel rail to swap injectors, how risky is that?
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Feb 7, 2015 18:02
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revmoo posted:Tried swapping plugs and wires, no change. Dizzy is OEM. Shouldn't be too bad. The biggest risk is tearing the oring seals. Which are dirt cheap.
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Feb 7, 2015 18:04
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Went ahead and pulled the rail and swapped injectors. No change. I took it for a spin and realized its not a 100% misfire like I thought, the issue goes away on high revs. Replacing alternator at the moment.
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Feb 7, 2015 19:31
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Replaced alternator. Took the car for a spin, running excellent, no misfire. Drive around for ten minutes and as we get back to the house the gauge on the A-pillar is showing 12 volts. Connect multimeter. 12.5 volts. What the gently caress? Also fu Honda for making owners put their alternators through this gap:  Btw confirmed thermostat ground is connected and clean.
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Feb 7, 2015 21:46
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revmoo posted:Replaced alternator. Took the car for a spin, running excellent, no misfire. Drive around for ten minutes and as we get back to the house the gauge on the A-pillar is showing 12 volts. Connect multimeter. 12.5 volts. I always put them in from the bottom on the D series, maybe I'm magical. I would have said check the thermostat ground as a previous poster said, but that's normally for a no start condition, which is usually the ECU not grounding. Really though, it's usually a cracked / corroded ECU. At least, that was what it was for me on my last EG. Stupid question : Can't see it in the pictures, but is the valvecover ground hooked up? That ground *IS* very much necessary. You can also try cleaning the the battery grounds where they connect to the unibody. Check the ground straps for corrosion, or at least check them for resistance.
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Feb 7, 2015 22:07
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This is a mini-me swap with the D16z6 head and it doesn't have a ground on the VC anymore. The ground has been run to the PS pump instead and has run fine for a couple months up until this point. I watched while my buddy drove it and it seemed like the volts would jump to 14 when shifting and then drop to 12.5 while accelerating. It's definitely a very intermittent issue and it is interesting that it persists with a different alternator.
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Feb 7, 2015 22:29
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revmoo posted:Replaced alternator. Took the car for a spin, running excellent, no misfire. Drive around for ten minutes and as we get back to the house the gauge on the A-pillar is showing 12 volts. Connect multimeter. 12.5 volts. You are supposed to pull the alternator through the bottom, but it sucks just as much as the top unless you pull an axle. From what you said, you are getting a solid white spark from #1-3 and an orange spark from #4? I also saw you were grounding against the body, try grounding the threads against the valve cover bolts instead, that is where they pull ground normally. Try cleaning the valve cover to body ground, the front and rear transmission grounds, and the negative terminal ground off of the battery. If that doesn't fix it you are going to need a known good or new distributor to test it out. One of your parts stores might have one in stock. (You'll need one from a civic si or del sol si, assuming you are working with a D15 with a Z6 head) If that doesn't fix it, it is most likely your ECU. edit: revmoo posted:This is a mini-me swap with the D16z6 head and it doesn't have a ground on the VC anymore. The ground has been run to the PS pump instead and has run fine for a couple months up until this point. Ignore all of the above and reconnect the valve cover ground first. edit 2: and double check the rest of the grounds are still there. edit 3: I worked on a CRX that someone did a wire tuck on and didn't want any engine grounds, the car ran fine except when under hard acceleration because the ECU was only really grounded through the engine mounts since there were no grounding straps on the motor. When the motor tilted from acceleration, the ECU lost ground and eventually fried itself causing a bunch of strange issues. doogle fucked around with this message at 22:44 on Feb 7, 2015 |
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Feb 7, 2015 22:39
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Fixed it! It was the ground. Holy poo poo. It was the ground that used to run to the VC that had been moved to the PS pump. Upon closer inspection it had one of those powdercoated washers on it. It was totally unnecessary. I ground off all of the contact points and refitted everything and the car drives like a dream now. Crazy stuff. Who puts a painted washer on an engine ground?!
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Feb 8, 2015 00:44
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revmoo posted:Fixed it! For no spark/inconsistent spark on a honda, you should always ground the plugs on the VC to ensure the head is actually grounded. Honda people do crazy poo poo with ground wires for some reason.
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Feb 8, 2015 04:22
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doogle posted:Honda people do crazy poo poo with ground wires for some reason. Seriously. Who ever thought that this would be acceptable must have been dropped on the head as a baby. 
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Feb 8, 2015 16:16
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