Guys, would incredibly bad ground wire cause random misfire at idle?
Had this used Fit for a little over a year now, 6 months ago MPG start going bad, and about 3 months ago I get this random misfire at idle.

It usually happen when I am at a stop light, and sometimes it happen, usually once every 2 lights, happens almost daily. I do drive short trips though, is only 15 min trip in the morning going to train station, and 15 minutes back at night. On highway or while it is moving, it drives fine... only feels gutless...

The engine was noisy, so I did valve adjustment last night (helped a bit with the noise), and I noticed the ground wire (left side of the engine going to the left bracket near the fender) were incredibly corroded, it has nearly 0.5mm rust on it, the bracket itself was super corroded, so is the bracket to frame...

So I took my ground wire and bracket out, filed out all the rust and wire-brushed it as clean as possible, same thing for the ground wire contact point. After my valve adjustment I took it out for a spin, noticed a slightly better power output (could just be my buttdyno) and it knocked ONCE. BUT THEN, it HAS NOT knock AT ALL last night and all day today.

My question is, would a super bad ground cause the engine to lose power and to random misfire at idle?

I will see tomorrow if it gets knock or not... if not, then I have some 1GA copper ground wire laying around (just need to get some copper ends) and may try to replace the ground wire all together.

Wires inside the loom were greenish as well...




Before grinding


After cleaning

 

replace the ground wires asap and run as many as you can from the (-) terminal . You wouldn't believe the problems that come from bad grounds:P

 

Well is always good to have good grounds, but I just want to isolate/confirm the problems here. Because my Fit is reaching 100k (99.1k right now lol) and I want to know whether I should bring it to dealer.

Would bad ground causes MPG to significantly suffer as well? They advertised like 7L/100km, mine is taking 10L...

 

misfiring is usually called by bad spark plugs or faulty coil packs. replace them ASAP. i had your symptoms before. at first, i thought it was the coil packs...but it was the SPARK PLUGS. faulty grounding may be a cause....but it doesnt relate to the suffering MPG problem and misfiring.

 

Spark plugs are brand new. I thought it might be the coil pack but I don't want to dump a couple of hundreds $ on the coil packs before i exhaust other problems. I've already tried cleaning the O2 sensor (using the civic O2 sensor cleaning trick)...

 

I had a member tell me that she had put a grounding kit on an older Honda that she had and could feel a difference in the way it ran.. I haven't had any wires or anything else become rusty on my car yet but it is inside the barn if it isn't being driven.. I've already bought some bulk cable to install if I ever have problems... I would assume that there was an ignition problem if my car was running rough at idle... The ignition systems are much higher voltage than in the old days and there is more dwell time at idle that causes it to be even higher than when at higher RPM and more capable of leaking to ground and causing a miss... The only place that is going to happen is at one of the coils... I have all of mine off right now and I will lube up the rubber boots with dielectric grease before I put everything back together... I would think that a car that is driven a lot in stop and go traffic would be having coil problems sooner than a car that doesn't idle as much... It gets real hot back where the coils are.

 

Ok, I will give that dielectric grease trick a try, I read it from another thread here, but haven't got around to buy extra grease yet. Also did you mean applying the grease to just the spirals in the coil pack? I don't see how the sparks could travel through the rubber though?

 

The rubber is probably leaking current at idle like old spark plug cables do when there is higher voltage going through them at low RPM at idle.. If so the arcing of current to ground will cause the winding of the coil to overheat and break or burn out... There is 50,000 or more volts building up in the coils and it can jump quite a ways to reach a grounded surface before reaching the spark plugs....

 

Second day, no knock/misfire. Knock on wood. I bought 2 packs of dielectric grease, but don't have time to apply it yet. And I couldn't find any place that sell copper ring connector to hook up with my 1GA wire... Will see in the upcoming day.

 

Open hood on dark night, should see arcing if it is, green copper wires equals rust of iron wires, use the connection grease on the contact area. Radio shack used to sell a high voltage insulating material you could paint on the wires and boots.

 

Alright, no misfire today. I also applied dielectric grease at the pink rubber boot area, inside and outside. Lets hope it was just a ground issue, and that with the grease it will cure the problem.

 

Hey, did putting dielectric grease fix your problem entirely?? My 07 Fit with 105K miles started running fairly rough at idle, I already had the valve clearance adjusted and it runs better but still runs rough at idle.

 

I thought it went away, but 3-4 days later the stupid misfire came back...
But the occurrence of the misfire did diminished though, from once a day to once couple of days. I highly doubt the dielectric grease did anything, if anything it would be cleaning my ground. Is your ground wire totally corroded too? (left side corner of your valve cover)

Next thing on my list, would be to replace my ground wire with a 1GA wire + copper ends. Then if that still doesn't solve it, I guess i will just gap my plug down a little.

Could someone show us where EXACTLY we should apply the dielectric grease on the boot? Is it the WHOLE COP or just the lower soft rubber part?

 

Honda's are know for idle misfires. Its was common with all my Honda cars. I can tell you its a lean condition and the timing is fluctuation. If it gets real bad I will put on the A/C to load the motor and it stops. It also happens when the weather changes and when I get off the highway. I can go months with no issues and I was never worried about it. I have a ultra gauge so I can see the conditions.

 

Honda ecus are slow to adjust and when conditions change it will hunt for proper tuning. There might be carbon build up especially on the 4th valve soaking up the fuel causing a lean condition. The best way to fix that make sure the motor is at temp and drive above 3500 to operated that 4th valve to clean the carbon build up.

 

Then I think you are just unlucky. I previously owned a 1992 Integra, and currently a 1999 Integra and 2007 Fit. My dad also had a 2004 Odyssey back then. My friend have a S2000, and another friend have a CSX. None of them have idle misfire.

How do you properly reset the ECU with the Fit? I pulled the battery terminal for 5 minutes when I first got the car to try to reset it. Is there a fuse for that? I hardly work on the Fit lol... I spend most of my time working on my Integra. XD

 

Hey I figured out the problem, I searched/read alot about the ignition coils going bad. I ordered new beck arnley coils and put them in yesterday and ALL symptoms of bad idle are gone!!! I was just going to replace the faulty one but didn't want to mess with it in the future anymore, unless these ones crap out of course, but they seem like good quality and they're made in Japan. The oem brand is garbage and they are Hitachi brand which napa sells. I read that Member "JoeF" bought them cheap and he still had the same problem with the news ones so I decided not to get those. I already had new plugs and did the valve clearance adjustment before replacing the coils but now that i put the new coils in, man the car runs like brand new again! I re-fell in love with my Fit again, lol. It's crazy, how much of a headache those crappy things give to everyone who has a Fit.

I was able to get that one hitachi coil to fail completely too by having a large electrical load at idle. I turned up the A/C full blast, turned on the lights, turned up my subwoofer and rolled up the windows after that it stopped working and finally it threw a code which cylinder was the culprit, so you can prob use this method if you want to just buy one ignition coil. If you do this its probably best to already have a new one on hand though.

 

Bad grounds in the right place means less voltage to the coil; less voltage, less spark; less spark more misfire.

 

Can you post where you got yours?

 

I got them from amazon,they have a blue tip tho, the picture shows a red tip.

Amazon.com: Beck Arnley 178-8374 Direct Ignition Coil: Automotive

Oh and I've never cleaned my ground but I did add a 8 gauge wire on top of the factory one cuz i have a subsoofer and it also ran a little better after that. The factory one to the block isn't even insulated and seems to be a light gauge. So this can prob help the car run a bit better.